Graphdiyne: Bridging SnO2 and Perovskite in Planar Solar Cells

Advancing SnO2 Electron Transport Layer for Efficient Perovskite Photovoltaics: A Critical Review

Currently, the latest photovoltaic technology based on perovskite solar cells (PSCs) has attracted much attention due to the low cost, exciting power conversion efficiency of over 26%, large scalability, and flexibility of PSCs. During the development course, optimization of the electron transport layer (ETL) plays an important role in boosting the photovoltaic performance of PSCs, where the use and modification of SnO2 with high chemical stability, low-temperature processability, and suitable energy band levels substantially are shown to solve the problems of poor charge transport, perovskite crystallization, and inferior stability at the PSC interface. Herein, we dedicate ourselves to providing a comprehensive review of the advanced development of the SnO2 ETL for realizing efficient PSCs. The fundamental properties of SnO2 and its key problems as an ETL in PSCs are summarized first. Then, the typical preparation methods are introduced, including chemical routes and physical routes. Sequentially, the state-of-the-art strategies for optimizing the quality of the SnO2 ETL are discussed, such as defect regulation, self-assembled monolayer modification, and double ETL construction. Finally, we shed some light on the existing challenges and future research directions for the large-scale development of SnO2-based PSCs.

Heterocyclic Conjugated Polydentate Ligands Facilitate Interfacial Charge Transfer of Air-Processed Carbon-Based All Inorganic Perovskite Solar Cells with an Efficiency Over 15

Modulating the charge transfer at the buried interface is crucial in carbon-based all-inorganic perovskite solar cells(C-PSCs). Nevertheless, most traditional organic modifiers present monofunctional and insulating characteristics which can impede charge transport potentially. Herein, a multifunctional heterocyclic conjugated polydentate modifier 4-imidazolylacrylic acid (UA) was proposed to modify buried interface. The results indicate that UA act as multifunctional roles due to its electron delocalization and polydentate feature, including increase the conductivity of tin oxide film, passivate interfacial defects, suppress recombination, enhance the energy level alignment, strengthen charge transport and eventually enable high performance C-PSCs prepared in air. Consequently, champion device present significant improvement in open circuit voltage (1.26 V), short circuit current density (15.69 mA cm-2), and fill factor (79%) after UA modification, and the power conversion efficiency (PCE) increased from 11.91% to 15.56% compared to the control device. Furthermore, long-term stability of unencapsulated UA modified device maintains 80.59% of initial efficiency in glove box after 800 h and 82.86% of initial efficiency in air after 400 h, exhibiting better stability than the control device. This research offers an innovative idea to facilitate charge transfer in buried interface of C-PSCs via conjugated polydentate ligand modification.

2,2'-Bipyridyl-4,4'-Dicarboxylic Acid Modified Buried Interface of High-Performance Perovskite Solar Cells

The regulation of interfaces remains a critical and challenging aspect in the pursuit of highly efficient and stable perovskite solar cells (PSCs). Here, 2,2'-bipyridyl-4,4'-dicarboxylic acid (HBPDC) is incorporated as an interfacial layer between SnO2 and perovskite layers in PSCs. The two carboxylic acid moieties on HBPDC bind to SnO2 through esterification, while its nitrogen atoms, possessing lone electron pairs, interact with uncoordinated lead (Pb2+) atoms through Lewis acid-base interactions. This dual functionality enables simultaneous passivation of surface defects on both the SnO2 and buried perovskite layers. In addition, the electron-deficient nature of HBPDC enhances interfacial energy band alignment and facilitates electron transfer from the perovskite to SnO2. Furthermore, the incorporation of HBPDC strengthens the interfacial adhesion, improving mechanical reliability. As a result, the PSCs exhibited an impressive power conversion efficiency (PCE) of 25.41 % under standard AM 1.5G conditions, along with remarkable environmental stability.

Multifunctional Graphdiyne Enables Efficient Perovskite Solar Cells via Anti-Solvent Additive Engineering

Finding ways to produce dense and smooth perovskite films with negligible defects is vital for achieving high-efficiency perovskite solar cells (PSCs). Herein, we aim to enhance the quality of the perovskite films through the utilization of a multifunctional additive in the perovskite anti-solvent, a strategy referred to as anti-solvent additive engineering. Specifically, we introduce ortho-substituted-4'-(4,4″-di-tert-butyl-1,1':3',1″-terphenyl)-graphdiyne (o-TB-GDY) as an AAE additive, characterized by its sp/sp2-cohybridized and highly π-conjugated structure, into the anti-solvent. o-TB-GDY not only significantly passivates undercoordinated lead defects (through potent coordination originating from specific high π-electron conjugation), but also serves as nucleation seeds to effectively enhance the nucleation and growth of perovskite crystals. This markedly reduces defects and non-radiative recombination, thereby increasing the power conversion efficiency (PCE) to 25.62% (certified as 25.01%). Meanwhile, the PSCs exhibit largely enhanced stability, maintaining 92.6% of their initial PCEs after 500 h continuous 1-sun illumination at ~ 23 °C in a nitrogen-filled glove box.

Improved self-powered perovskite CH3NH3PbI3/SnO2 heterojunction photodetectors achieved by interfacial engineering with a synergic effect

Lead halide perovskite heterojunctions have been considered as important building blocks for fabricating high-performance photodetectors (PDs). However, the interfacial defects induced non-radiative recombination and interfacial energy-level misalignment induced ineffective carrier transport severely limit the performance of photodetection of resulting devices. Herein, interfacial engineering with a spin-coating procedure has been studied to improve the photodetection performance of CH3NH3PbI3/SnO2 heterojunction PDs, which were fabricated by sputtering a SnO2 thin film on ITO glass followed by spin-coating a CH3NH3PbI3 thin film. It has shown that spin-coating of a SnO2 layer on the sputtered SnO2 thin films suppressed the surface oxygen vacancies of SnO2 thin films and up-shifted their conduction band, which suppressed the interfacial non-radiative recombination and enhanced the carriers transport at the CH3NH3PbI3/SnO2 interface, respectively. Accordingly, improved photodetection performance, such as the reduced dark current and increased photocurrent, has been observed in the CH3NH3PbI3/SnO2 heterojunction PDs, where the responsivity and detectivity of 0.077 A W-1 and 2.0 × 1011 jones, respectively, at the zero bias have been demonstrated. These results show a simple way to suppress the interfacial non-radiative recombination and enhance the carrier transport at the interface to fabricate improved perovskite heterojunction PDs in the future.

Universal Approach for Managing Iodine Migration in Inverted Single-Junction and Tandem Perovskite Solar Cells

Despite significant progress in the power-conversion efficiency (PCE) of perovskite solar cells (PSCs), the instability of devices remains a considerable obstacle for commercial applications. This instability primarily originates from the migration of halide ions-particularly iodide ions (I-). Under light exposure and thermal stress, I- migrates and transforms into I2, leading to irreversible degradation and performance loss. To address this issue, we introduced the additive 2,1,3-benzothiadiazole,5,6-difluoro-4,7-bis(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl) (BT2F-2B) into the perovskite. The strong coordination between the unhybridized p orbital and lone-pair electrons from I- inhibits the deprotonation of MAI/FAI and the subsequent conversion of I- to I₂. The highly electronegative fluorine enhances its electrostatic interaction with I-. Consequently, the synergistic effect of BT2F-2B effectively suppresses the decomposition of perovskite and the defect density of the iodide vacancies. This approach delivers a PCE over 26% for inverted single-junction PSCs, with exceptional operational stability. According to the ISOS-L-3 testing protocol (maximum power point tracking at 85 °C and 50% relative humidity), treated PSCs retain 85% of their original PCE after 1000 h of aging. When the BT2F-2B is applied to a wide-bandgap (1.77 eV) perovskite system, the PCE of all-perovskite tandem solar cells reaches 27.8%, confirming the universality of the proposed strategy.

Effect of Guanidinium Salt for Stress-Relaxation and Interfacial Engineering in Antisolvent Free Perovskite Solar Cells Fabricated Under Air Ambient

In perovskite solar cells, the presence of stress and defects at interfaces promotes performance degradation and poor stability of the devices. The formation of these defects is more prominent in two-step antisolvent-free perovskite film fabrication. This study addresses these challenges by introducing guanidine sulfate (Gua-S) at the tin oxide/formamidinium lead iodide perovskite interface, fabricated without antisolvent under ambient air. Interfacial Gua-S enhanced morphology by forming bonds between uncoordinated Pb2+ ions and I- vacancies at the interface and showed improvement in the crystallinity and quality of the perovskite film. Microstructural stress analysis indicated a substantial reduction in stress, decreasing from 50.6 to 20.72 MPa with the application of Gua-S. Moreover, the Gua-S treated solar cells showed significant improvements and achieved an open circuit voltage of 1.08 V and 22.34% efficiency. Further, electrochemical impedance spectroscopic analysis showed improved built-in potential, carrier lifetime, and charge recombination lifetime for treated devices. The devices retained over 87% of the initial power conversion efficiency after 2000 hours of operation. This comprehensive study addresses the fundamental issues of interfacial stress and defects in perovskite solar cells and demonstrates the efficacy of Gua-S salt in enhancing both the structural and functional aspects of the antisolvent-free device fabrication process.

Oxide Derivatives of Nb2CTx MXene and Their Application as Electron Transport Layers in Perovskite Solar Cells: Unraveling the Oxidation Process and Functionalization

In the realm of photovoltaic research, 2D transition metal carbides (MXenes) have gained significant interest due to their exceptional photoelectric capabilities. However, the instability of MXenes due to oxidation has a direct impact on their practical applications. In this work, the oxidation process of Nb2CTx MXene in aqueous systems is methodically simulated at the atomic level and nanosecond timescales, which elucidates the structural variations influenced by the synergistic effects of water and dissolved oxygen, predicting a transition from metal to semiconductor with 44% C atoms replaced by O atoms in Nb2CTx. Moreover, Nb2CTx with varying oxidation degrees is utilized as electron transport layers (ETLs) in perovskite solar cells (PSCs). Favorable energy level alignments with superior electron transfer capability are achieved by controlled oxidation. By further exploring the composites of Nb2CTx to its derivatives, the strong interaction of the nano-composites is demonstrated to be more effective for electron transport, thus the corresponding PSC achieves a better performance with long-term stability compared with the widely used ETLs like SnO2. This work unravels the oxidation dynamics of Nb2CTx and provides a promising approach to designing ETL by exploiting MXenes to their derivatives for photovoltaic technologies.

Bottom-Up Defect Modification Through Oily-Allicin Modified Buried Interface Achieving Highly Efficient and Stable Perovskite Solar Cells

The buried interface properties of the perovskite solar cells (PSCs) play a crucial role in the power conversion efficiency (PCE) and operational stability. The metal-oxide/perovskite heterogeneous interfaces are highly defective and cause serious ion migration. However, the buried and unexposed bottom interface and simultaneous stabilization of grain boundaries receive less attention and effective solutions. To tackle this problem, a solid-liquid strategy is employed by introducing oily-additive allicin at the buried interface to passivate the shallow (VI and Vo) and deep traps (VPb and PbI). Interestingly, oily status allicin fills the pinholes at the heterointerface and wraps the perovskite grains, suppressing the ion migration during the photoaging process. As a result, an outstanding PCE of 25.07% is achieved with a remarkable fill factor (FF) of 84.03%. The modified devices can maintain 94.51% of the original PCE after light soaking under 1-sun illumination for 1000 h. This work demonstrates a buried interface modification method that employs an eco-friendly additive, which helps promote the development of PSCs with high performance and stability.

Revealing the Roles of Guanidine Hydrochloride Ionic Liquid in Ion Inhibition and Defects Passivation for Efficient and Stable Perovskite Solar Cells

As a result of full-scale ongoing global efforts, the power conversion efficiency (PCE) of the organic-inorganic metal halide perovskite has skyrocketed. Unfortunately, the long-term operational stability for commercialization standards is still lagging owing to intrinsic defects such as ion migration-induced degradation, undercoordinated Pb2+, and shallow defects initiated by disordered crystal growth. Herein, we employed multifunctional, non-volatile tetra-methyl guanidine hydrochloride [TMGHCL] ionic liquid (IL) as an additive to elucidate defects' passivation effects on organic-inorganic metal halide perovskite. More specifically, the formation of hydrogen bonds between H+ in GA+ and I- and coordinate bonding between Cl- and undercoordinated Pb2+ could significantly passivate these defects. The hypothesis was confirmed by both experimental and DFT simulations displaying that the optimized ratio of IL integration restrains ion migration, improving grains' size, and significantly elongating the carrier lifetime. Remarkably, the modified cell achieved a peak efficiency of 22.00 % with negligible hysteresis, compared to the control device's PCE of 20.12 %. In addition, the TMGHCL-based device retains its 93.29 % efficiency after 16 days of continuous exposure to air with a relative humidity of 35±5% and temperature of 25±5 °C. This efficient approach of adding IL to perovskites absorber can produce high PCE and has strong commercialization potential.

Recent Advances in Interface Engineering for Enhanced Open-Circuit Voltage Regulation in Perovskite Solar Cells

In recent years, perovskite solar cells (PSCs) have attracted significant attention due to their excellent photoelectric properties. However, several key performance parameters of these devices still fall short of their theoretical limits. Among these parameters, the regulation of open-circuit voltage (VOC) has been a focal point of intensive research efforts, playing a pivotal role in advancing the efficiency of PSCs. This review first provides an overview of the generation and loss mechanism of VOC. It then discusses the significance of interface engineering in VOC regulation. Recent developments in high-efficiency PSCs realized via interface engineering have been summarized and categorized into three key areas: surface modification, interface structure optimization, and surface dimensional engineering. Finally, a comprehensive summary of past research in this domain and offered insights into the future prospects of enhancing VOC in PSCs is provided.

Residual Stress Mitigation in Perovskite Solar Cells via Butterfly-Inspired Hierarchical PbI2 Scaffold

Residual stress in metal halide perovskite films intimately affects the photovoltaic figure of merit and longevity of perovskite solar cells. A delicate management of the crystallization kinetics is critical to the preparation of high-quality perovskite films. Only very limited methods, however, are available to regulate the residual stress of a perovskite film in a controllable manner, particularly for a perovskite film fabricated by a two-step method. Here, we demonstrate the construction of a hierarchical PbI2 scaffold inspired by Archaeoprepona demophon butterfly by combining an interlayer guided growth of porous structure and nanoimprinting. The hierarchically structured PbI2 that emulates the physical structure of the butterfly wing scale permits unimpeded permeation of organic amine salts and sufficient space for volume expansion during the crystallization process, accompanied by preferential perovskite growth of a defectless (001) crystal plane. The optimized perovskite film outperforms the control with reduced residual stress and defect density. Consequently, perovskite solar cells with a respectable power conversion efficiency reaching 23.4% (certified 23%) and an impressive open-circuit voltage of 1.184 V can be achieved. The target device can maintain 80% of initial efficiency after maximum power point tracking under illumination for 700 h. This work expands the range of engineering toward PbI2 by exploring a simultaneously tailored morphology and crystallinity and highlights the significance of a hierarchical PbI2 scaffold as an alternative choice to mitigate residual stress in a two-step processed perovskite active layer and boost the longevity of perovskite solar cells.

Exciton Localization Modulated by Ultradeep Moiré Potential in Twisted Bilayer γ-Graphdiyne

Twisted moiré superlattice is featured with its moiré potential energy, the depth of which renders an effective approach to strengthening the exciton-exciton interaction and exciton localization toward high-performance quantum photonic devices. However, it remains as a long-standing challenge to further push the limit of moiré potential depth. Herein, owing to the pz orbital induced band edge states enabled by the unique sp-C in bilayer γ-graphdiyne (GDY), an ultradeep moiré potential of ∼289 meV is yielded. After being twisted into the hole-to-hole layer stacking configuration, the interlayer coupling is substantially intensified to augment the lattice potential of bilayer GDY up to 475%. The presence of lateral constrained moiré potential shifts the spatial distribution of electrons and holes in excitons from the regular alternating mode to their respective separated and localized mode. According to the well-established wave function distribution of electrons contained in excitons, the AA-stacked site is identified to serve for exciton localization. This work extends the materials systems available for moiré superlattice design further to serial carbon allotropes featured with benzene ring-alkyne chain coupling, unlocking tremendous potential for twistronic-based quantum device applications.

Fluorinated organic ammonium salt passivation for high-efficiency and stable inverted CsPbI2Br perovskite solar cells

All-inorganic CsPbI2Br inverted perovskite solar cells (PSCs) have drawn increasing attention because of their outstanding thermal stability and compatible process with tandem cells. However, relatively low open circuit voltage (Voc) has lagged their progress far behind theoretical limits. Herein, we introduce phenylmethylammonium iodide and 4-trifluoromethyl phenylmethylammonium iodide (CFPMAI) on the surface of a CsPbI2Br perovskite film and investigate their passivation effects. It is found that CFPMAI with a -CF3 substituent significantly decreases the trap density of the perovskite film by forming interactions with the under-coordinated Pb2+ ions and effectively suppresses the non-radiative recombination in the resulting PSC. In addition, CFPMAI surface passivation facilitates the optimization of energy-level alignment at the CsPbI2Br perovskite/[6,6]-phenyl C61 butyric acid methyl ester interface, resulting in improved charge extraction from the perovskite to the charge transport layer. Consequently, the optimized inverted CsPbI2Br device exhibits a markedly improved champion efficiency of 14.43% with a Voc of 1.12 V, a Jsc of 16.31 mA/cm2, and a fill factor of 79.02%, compared to the 10.92% (Voc of 0.95 V) efficiency of the control device. This study confirms the importance of substituent groups on surface passivation molecules for effective passivation of defects and optimization of energy levels, particularly for Voc improvement.

Localized Oxidation Embellishing Strategy Enables High-Performance Perovskite Solar Cells

Perovskite solar cell (pero-SC) has attracted extensive studies as a promising photovoltaic technology, wherein the electron extraction and transfer exhibit pivotal effect to the device performance. The planar SnO2 electron transport layer (ETL) has contributed the recent record power conversion efficiency (PCE) of the pero-SCs, yet still suffers from surface defects of SnO2 nanoparticles which brings energy loss and phase instability. Herein, we report a localized oxidation embellishing (LOE) strategy by applying (NH4 )2 CrO4 on the SnO2 ETL. The LOE strategy builds up plentiful nano-heterojunctions of p-Cr2 O3 /n-SnO2 and the nano-heterojunctions compensate the surface defects and realize benign energy alignment, which reduces surface non-radiative recombination and voltage loss of the pero-SCs. Meanwhile, the decrease of lattice mismatch released the lattice distortion and eliminated tensile stress, contributing to better stability of the devices. The pero-SCs based on α-FAPbI3 with the SnO2 ETL treated by the LOE strategy realized a PCE of 25.72 % (certified as 25.41 %), along with eminent stability performance of T90 >700 h. This work provides a brand-new view for defect modification of SnO2 electron transport layer.

Improved Photovoltaic Performance of Inverted Two-Dimensional Perovskite Solar Cells via a Simple Molecular Bridge on Buried Interface

NiOx-based two-dimensional perovskite solar cells (2D-PSCs) have the advantages of low fabrication temperature, suitable energy level matching, suppressed hysteresis, and superior stability, while the poor interfacial contacts between NiOx and perovskite layers limit the perovskite film growth and charge transfer. Herein, a simple molecule, urea, was used as a molecular modifier to form bifacial passivation on the buried interface of NiOx/perovskite, resulting in better interfacial contact and efficient bifacial passivation. We demonstrated that efficient bifacial passivation mainly comes from strong interactions between urea and NiOx or perovskite, which make urea a molecular bridge for smoother charge transfer. Moreover, urea can regulate the ratio of Ni3+/Ni2+, therefore boosting the conductivity of NiOx, and adjust the morphology of the NiOx film for better 2D-perovskite crystal growth. Besides, urea also passivates the bifacial defect states of both NiOx and perovskite film, yielding reduced defect density of the perovskite film and superior charge transfer on the buried interface. Consequently, inverted 2D-PSCs with urea modification proved significant improvements in short-circuit current density and fill factor, resulting in improved power conversion efficiency from 14.64 to 16.84% with better stability in air.

Passivating SnO2/perovskite interface via guanide hydrochloride toward efficient and stable n-i-p perovskite solar cells

Nonradiation recombination of interfacial carriers is a key factor hindering the improvement of efficiency and stability of perovskite solar cells (PSCs). Here, we report an effective electron transport layer/perovskite interface regulation strategy. By introducing the multifunctional molecule guanidine hydrochloride (GCl) on the surface of SnO2, we can enhance the electron extraction between SnO2 and perovskite and promote the growth of high-quality perovskite films. GCl is anchored on the surface of SnO2 and interacts with undercoordinated ions in perovskite. The experimental results show that GCl has interaction with both SnO2 and perovskite layer, and a "bridge" connection is formed between the two layers. This strategy not only passivates the SnO2/perovskite interface defects, improves the perovskite crystallization quality, but also helps to reduce the interface charge accumulation. More importantly, the PCE of GCl passivated device reached 21.63 %, which was much better than that of control device (19.56 %). In the air environment, after 30 days at room temperature, the GCl modified unpackaged device maintained 83 % of its initial efficiency. Therefore, interface modification with GCl is an effective strategy to improve the interface state, improve the crystallization quality and obtain high-performance PSCs.

Growth and Dispersion Control of SnO2 Nanocrystals Employing an Amino Acid Ester Hydrochloride in Solution Synthesis: Microstructures and Photovoltaic Applications

Tin oxide (SnO2) is a technologically important semiconductor with versatile applications. In particular, attention is being paid to nanostructured SnO2 materials for use as a part of the constituents in perovskite solar cells (PSCs), an emerging renewable energy technology. This is mainly because SnO2 has high electron mobility, making it favorable for use in the electron transport layer (ETL) in these devices, in which SnO2 thin films play a role in extracting electrons from the adjacent light-absorber, i.e., lead halide perovskite compounds. Investigation of SnO2 solution synthesis under diverse reaction conditions is crucial in order to lay the foundation for the cost-effective production of PSCs. This research focuses on the facile catalyst-free synthesis of single-nanometer-scale SnO2 nanocrystals employing an aromatic organic ligand (as the structure-directing agent) and Sn(IV) salt in an aqueous solution. Most notably, the use of an aromatic amino acid ester hydrochloride salt-i.e., phenylalanine methyl ester hydrochloride (denoted as L hereafter)-allowed us to obtain an aqueous precursor solution containing a higher concentration of ligand L, in addition to facilitating the growth of SnO2 nanoparticles as small as 3 nm with a narrow size distribution, which were analyzed by means of high-resolution transmission electron microscopy (HR-TEM). Moreover, the nanoparticles were proved to be crystallized and uniformly dispersed in the reaction mixture. The environmentally benign, ethanol-based SnO2 nanofluids stabilized with the capping agent L for the Sn(IV) ions were also successfully obtained and spin-coated to produce a SnO2 nanoparticle film to serve as an ETL for PSCs. Several SnO2 ETLs that were created by varying the temperature of nanoparticle synthesis were examined to gain insight into the performance of PSCs. It is thought that reaction conditions that utilize high concentrations of ligand L to control the growth and dispersion of SnO2 nanoparticles could serve as useful criteria for designing SnO2 ETLs, since hydrochloride salt L can offer significant potential as a functional compound by controlling the microstructures of individual SnO2 nanoparticles and the self-assembly process to form nanostructured SnO2 thin films.

Dual-Interface Engineering in Perovskite Solar Cells with 2D Carbides

Passivating the interfaces between the perovskite and charge transport layers is crucial for enhancing the power conversion efficiency (PCE) and stability in perovskite solar cells (PSCs). Here we report a dual-interface engineering approach to improving the performance of FA0.85 MA0.15 Pb(I0.95 Br0.05 )3 -based PSCs by incorporating Ti3 C2 Clx Nano-MXene and o-TB-GDY nanographdiyne (NanoGDY) into the electron transport layer (ETL)/perovskite and perovskite/ hole transport layer (HTL) interfaces, respectively. The dual-interface passivation simultaneously suppresses non-radiative recombination and promotes carrier extraction by forming the Pb-Cl chemical bond and strong coordination of π-electron conjugation with undercoordinated Pb defects. The resulting perovskite film has an ultralong carrier lifetime exceeding 10 μs and an enlarged crystal size exceeding 2.5 μm. A maximum PCE of 24.86 % is realized, with an open-circuit voltage of 1.20 V. Unencapsulated cells retain 92 % of their initial efficiency after 1464 hours in ambient air and 80 % after 1002 hours of thermal stability test at 85 °C.

Construction of Reinforced Self-Cleaning and Efficient Photothermal PDMS@GDY@Cu Sponges toward Anticorrosion and Antibacterial Applications

Copper (Cu)-based materials are widely used in many fields from industry to life, including marine, medical apparatus and instruments, and microelectronic devices owing to their superior thermal, electrical, and mechanical properties. However, the interaction of copper with aggressive and fouling liquids under normal circumstances easily brings about severe bacterial accumulation, resulting in undesirable functionality degeneration and bacterial infections. In this contribution, we reported a novel copper-based sponge, polydimethylsiloxane (PDMS)@graphdiyne (GDY)@Cu, constructed by in situ synthesis of GDY on a commercial Cu sponge, followed by the modification of PDMS. The as-fabricated PDMS@GDY@Cu sponge not only possesses excellent self-cleaning activity against the pollution of daily drinks and dirt due to an improved static contact angle (~136°), but also display a remarkably enhanced anticorrosion performance, attributed to intimate coverage of chemically stable GDY and PDMS on the Cu sponge. Based on high photothermal effect of GDY, the PDMS@GDY@Cu sponge also displays significantly improved antibacterial activities under irradiation. In addition, due to excellent chemical stability of PDMS and GDY, self-cleaning behavior and photothermal-assisted antibacterial performance are well maintained after long-term attack of bacteria. These results demonstrate that GDY-based functional coatings hold great promises in the protection of copper devices under harsh conditions.

Graphdiyne-Based Multiscale Catalysts for Ammonia Synthesis

Graphdiyne, a sp/sp2 -cohybridized two-dimensional all- carbon material, has many unique and fascinating properties of alkyne-rich structures, large π conjugated system, uniform pores, specific unevenly-distributed surface charge, and incomplete charge transfer properties provide promising potential in practical applications including catalysis, energy conversion and storage, intelligent devices, life science, photoelectric, etc. These superior advantages have made graphdiyne one of the hottest research frontiers of chemistry and materials science and produced a series of original and innovative research results in the fundamental and applied research of carbon materials. In recent years, considerable advances have been made toward the development of graphdiyne-based multiscale catalysts for nitrogen fixation and ammonia synthesis at room temperatures and ambient pressures. This review aims to provide a comprehensive update in regard to the synthesis of graphdiyne-based multiscale catalysts and their applications in the synthesis of ammonia. The unique features of graphdiyne are highlighted throughout the review. Finally, it concludes with the discussion of challenges and future perspectives relating to graphdiyne.

Ir0/graphdiyne atomic interface for selective epoxidation

The development of catalysts that can selectively and efficiently promote the alkene epoxidation at ambient temperatures and pressures is an important promising path to renewable synthesis of various chemical products. Here we report a new type of zerovalent atom catalysts comprised of zerovalent Ir atoms highly dispersed and anchored on graphdiyne (Ir⁰/GDY) wherein the Ir⁰ is stabilized by the incomplete charge transfer effect and the confined effect of GDY natural cavity. The Ir⁰/GDY can selectively and efficiently produce styrene oxides (SO) by electro-oxidizing styrene (ST) in aqueous solutions at ambient temperatures and pressures with high conversion efficiency of ∼100%, high SO selectivity of 85.5%, and high Faradaic efficiency (FE) of 55%. Experimental and density functional theory (DFT) calculation results show that the intrinsic activity and stability due to the incomplete charge transfer between Ir⁰ and GDY effectively promoted the electron exchange between the catalyst and reactant molecule, and realized the selective epoxidation of ST to SO. Studies of the reaction mechanism demonstrate that Ir⁰/GDY proceeds a distinctive pathway for highly selective and active alkene-to-epoxide conversion from the traditional processes. This work presents a new example of constructing zerovalent metal atoms within the GDY matrix toward selective electrocatalytic epoxidation.

Two-Dimensional Carbon Graphdiyne: Advances in Fundamental and Application Research

Graphdiyne (GDY), a rising star of carbon allotropes, features a two-dimensional all-carbon network with the cohybridization of sp and sp² carbon atoms and represents a trend and research direction in the development of carbon materials. The sp/sp²-hybridized structure of GDY endows it with numerous advantages and advancements in controlled growth, assembly, and performance tuning, and many studies have shown that GDY has been a key material for innovation and development in the fields of catalysis, energy, photoelectric conversion, mode conversion and transformation of electronic devices, detectors, life sciences, etc. In the past ten years, the fundamental scientific issues related to GDY have been understood, showing differences from traditional carbon materials in controlled growth, chemical and physical properties and mechanisms, and attracting extensive attention from many scientists. GDY has gradually developed into one of the frontiers of chemistry and materials science, and has entered the rapid development period, producing large numbers of fundamental and applied research achievements in the fundamental and applied research of carbon materials. For the exploration of frontier scientific concepts and phenomena in carbon science research, there is great potential to promote progress in the fields of energy, catalysis, intelligent information, optoelectronics, and life sciences. In this review, the growth, self-assembly method, aggregation structure, chemical modification, and doping of GDY are shown, and the theoretical calculation and simulation and fundamental properties of GDY are also fully introduced. In particular, the applications of GDY and its formed aggregates in catalysis, energy storage, photoelectronic, biomedicine, environmental science, life science, detectors, and material separation are introduced.

Self-Generated Buried Submicrocavities for High-Performance Near-Infrared Perovskite Light-Emitting Diode

Embedding submicrocavities is an effective approach to improve the light out-coupling efficiency (LOCE) for planar perovskite light-emitting diodes (PeLEDs). In this work, we employ phenethylammonium iodide (PEAI) to trigger the Ostwald ripening for the downward recrystallization of perovskite, resulting in spontaneous formation of buried submicrocavities as light output coupler. The simulation suggests the buried submicrocavities can improve the LOCE from 26.8 to 36.2% for near-infrared light. Therefore, PeLED yields peak external quantum efficiency (EQE) increasing from 17.3% at current density of 114 mA cm-2 to 25.5% at current density of 109 mA cm-2 and a radiance increasing from 109 to 487 W sr-1 m-2 with low rolling-off. The turn-on voltage decreased from 1.25 to 1.15 V at 0.1 W sr-1 m-2. Besides, downward recrystallization process slightly reduces the trap density from 8.90 × 1015 to 7.27 × 1015 cm-3. This work provides a self-assembly method to integrate buried output coupler for boosting the performance of PeLEDs.

One-pot synthesis of gamma-graphyne supported Pd nanoparticles with high catalytic activity

As a unique member of the graphyne family, gamma-graphyne (γ-graphyne) is a novel kind of 2D carbon allotrope with potential high carrier mobility and large surface area. It remains a great challenge to synthesize graphynes with targeted topologies and good performance. Herein, a novel one-pot method was applied to the synthesis of γ-graphyne using hexabromobenzene and acetylenedicarboxylic acid via a Pd-catalyzed decarboxylative coupling reaction, which is easy to perform with mild reaction conditions, facilitating the possibility of mass production. As a result, the synthesized γ-graphyne reveals a two-dimensional γ-graphyne structure consisting of 1 : 1 sp/sp² hybridized carbon atoms. Furthermore, γ-graphyne as a carrier for Pd (Pd/γ-graphyne) displayed a superior catalytic activity for the reduction of 4-nitrophenol with a short reaction time and high yields, even in aqueous media under aerobic conditions. Compared with Pd/GO, Pd/HGO, Pd/CNT, and commercial Pd/C, Pd/γ-graphyne showed more excellent catalytic performance with lower palladium loadings. Thus we expect that the novel approach for the synthesis of γ-graphyne will boost research on the design and application of graphyne-type functional materials for catalysis.

Step by Step Induced Growth of Zinc-Metal Interface on Graphdiyne for Aqueous Zinc-Ion Batteries

Rechargeable aqueous zinc ion batteries (AZIBs) promise high energy density, low redox potential, low cost and safety; however, their cycle performances are seriously insufficient to restrict the progress in this field. We propose a new concept of atomic electrode formed on the graphdiyne (GDY). This new idea electrode was synthesized by selectively, uniformly, and stably anchoring Zn atoms on GDY at the beginning of plating. The Zn atoms are induced to grow into larger size Zn clusters, which continue to grow into nanoflat. Finally, a new heterojunction interface is formed on GDY without any Zn dendrites and side reactions, even at high current densities. Such stepwise induction of growth greatly suppresses the formation of Zn dendrites, resulting in high electroplating/stripping reversibility and lifespan of AZIBs.

Graphdiyne and Its Derivatives as Efficient Charge Reservoirs and Transporters in Semiconductor Devices

2D graphdiyne (GDY), which is composed of sp and sp² hybridized carbon atoms, is a promising semiconductor material with a unique porous lamellar structure. It has high carrier mobility, tunable bandgap, high density of states, and strong electrostatic interaction ability with ions and organic functional units. In recent years, interests in applying GDYs (GDY and its derivatives) in semiconductor devices have been growing rapidly, and great achievements have been made. Attractively, GDYs could act as efficient reservoirs and transporters for both carriers and ions, which endows them with enormous potential in future novel optoelectronics. In this review, the progress in this field is systematically summarized, aiming to bring an in-depth insight into the GDYs' intrinsic uniqueness. Particularly, the effects of GDYs on carrier dynamics and ionic interactions in various semiconductor devices are succinctly described, analyzed, and concluded.

Perylene Monoimide Phosphorus Salt Interfacial Modified Crystallization for Highly Efficient and Stable Perovskite Solar Cells

Reducing the interfacial defects of perovskite films is key to improving the performance of perovskite solar cells (PSCs). In this study, two kinds of perylene monoimide (PMI) derivative phosphonium bromide salts were designed and used as a multifunctional interface-modified layer in PSCs. These two molecules are inserted between SnO₂ and perovskite to produce a bidirectional passivation effect. The interaction with SnO₂ reduces the oxygen vacancy on the surface of SnO₂ and tunes the energy level of the electron transport layer, making more matches with the perovskite layer. The modified layer can promote the growth of perovskite crystals and reduce the interfacial defects of the perovskite film. Furthermore, the power conversion efficiency (PCE) of PSCs increased from 19.49 to 22.85%, and the open-circuit voltage (V_OC) increased from 1.06 to 1.14 V. At the same time, the PCE of the SnO₂/PMI-TPP-based device remained 88% of the initial PCE after 240 h of continuous illumination. In addition, these two PMI derivatives with a quasi-planar structure can improve the flexibility of flexible PSCs. This study provided a new strategy for the interfacial modification of PSCs and a new insight into the application of flexible PSCs.

Pushing the Limit of Open-Circuit Voltage Deficit via Modifying Buried Interface in CsPbI3 Perovskite Solar Cells

Although CsPbI₃ perovskites have shown tremendous potential in the photovoltaic field owing to their excellent thermal stability, the device performance is seriously restricted by severe photovoltage loss. The buried titanium oxide/perovskite interface plays a critical role in interfacial charge transport and perovskite crystallization, which is closely related to open-circuit voltage deficit stemming from nonradiative recombination. Herein, target molecules named 3-sulphonatopropyl acrylate potassium salts are deliberately employed with special functional groups for modifying the buried interface, giving rise to favorable functions in terms of passivating interfacial defects, optimizing energetic alignment, and facilitating perovskite crystallization. Experimental characterizations and theoretical calculations reveal that the buried interface modification inhibits the electron transfer barrier and simultaneously improves perovskite crystal quality, thereby reducing trap-assisted charge recombination and interfacial energetic loss. Consequently, the omnibearing modification regarding the buried interface endows the devices with an impressive efficiency of 20.98%, achieving a record-low V_OC deficit of 0.451 V. The as-proposed buried interface modification strategy renders with a universal prescription to push the limit of V_OC deficit, showing a promising future in developing high-performance all-inorganic perovskite photovoltaics.

MXene‐Regulated Perovskite Vertical Growth for High‐Performance Solar Cells

Defects at the interfaces of perovskite (PVK) thin films are the main factors responsible for instability and low photoelectric conversion efficiency (PCE) of PVK solar cells (PSCs). Here, a SnO2‐MXene composite electron transport layer (ETL) is used in PSCs to improve interfacial contact and passivate defects at the SnO2/perovskite interface. The introduced MXene regulates SnO2dispersion and induces a vertical growth of PVK. The lattice matching of MXene and perovskite suppresses the concentration of interfacial stress, thereby obtaining a perovskite film with low defects. Compared with SnO2‐based device, the PCE of SnO2‐MXene‐based device is improved by 15 % and its short‐circuit current is up to 25.07 mA cm−2. Furthermore, unencapsulated device maintained about 90 % of its initial efficiency even after 500 h of storage at 30–40 % relative humidity in ambient air. The composite ETL strategy provides a route to engineer interfacial passivation between metal halide perovskites and ETLs.

Controlled growth of a high selectivity interface for seawater electrolysis

Overall seawater electrolysis is an important direction for the development of hydrogen energy conversion. The key issues include how to achieve high selectivity, activity, and stability in seawater electrolysis reactions. In this report, the heterostructures of graphdiyne-RhO_x-graphdiyne (GDY/RhO_x/GDY) were constructed by in situ-controlled growth of GDY on RhO_x nanocrystals. A double layer interface of sp-hybridized carbon-oxide-Rhodium (sp-C∼O-Rh) was formed in this system. The microstructures at the interface are composed of active sites of sp-C∼O-Rh. The obvious electron-withdrawing surface enhances the catalytic activity with orders of magnitude, while the GDY outer of the metal oxides guarantees the stability. The electron-donating and withdrawing sp-C∼O-Rh structures enhance the catalytic activity, achieving high-performance overall seawater electrolysis with very small cell voltages of 1.42 and 1.52 V at large current densities of 10 and 500 mA cm^-2 at room temperatures and ambient pressures, respectively. The compositional and structural superiority of the GDY-derived sp-C-metal-oxide active center offers great opportunities to engineer tunable redox properties and catalytic performance for seawater electrolysis and beyond. This is a typical successful example of the rational design of catalytic systems.

Rhodium nanocrystals on porous graphdiyne for electrocatalytic hydrogen evolution from saline water

The realization of the efficient hydrogen conversion with large current densities at low overpotentials represents the development trend of this field. Here we report the atomic active sites tailoring through a facile synthetic method to yield well-defined Rhodium nanocrystals in aqueous solution using formic acid as the reducing agent and graphdiyne as the stabilizing support. High-resolution high-angle annular dark-field scanning-transmission electron microscopy images show the high-density atomic steps on the faces of hexahedral Rh nanocrystals. Experimental results reveal the formation of stable sp-C~Rh bonds can stabilize Rh nanocrystals and further improve charge transfer ability in the system. Experimental and density functional theory calculation results solidly demonstrate the exposed high active stepped surfaces and various metal atomic sites affect the electronic structure of the catalyst to reduce the overpotential resulting in the large-current hydrogen production from saline water. This exciting result demonstrates unmatched electrocatalytic performance and highly stable saline water electrolysis.

Cathode enabled high faradaic efficiency: reduction of imines to amines with H2O as a H-source

Benefiting from a high overpotential of the competitive hydrogen evolution reaction with a carbon paper cathode, the desired electrochemical reduction of imines was achieved with high faradaic efficiency by using H₂O as a H-source. With this sustainable atom-economic strategy, a series of potentially versatile amines were obtained in medium-to-high yields (49-86%).

SnO2 Passivation and Enhanced Perovskite Charge Extraction with a Benzylamine Hydrochloric Interlayer

Perovskite solar cells (PSCs) have gained much attention because of their expressive power conversion efficiency (PCE) of up to 25.5%. A good contact and a well-aligned energy level at the buried interfaces between electron transport layers (ETLs) and perovskite films play an essential role in promoting charge-carrier collection and suppressing nonradiative recombination. Currently, low-temperature-processed SnO₂ thin films are widely used as the ETLs to achieve efficient and stable planar PSCs. However, fabricating proper SnO₂/perovskite interfaces with a good contact and a well-aligned energy level is necessary but implies a great challenge. Herein, we modify the SnO₂ ETL using benzylamine hydrochloride (BH), which is expected to facilitate the energy level alignment and to enhance perovskite crystallization. Moreover, the BH interlayer is found to effectively reduce the trap-state density and thereby improve the charge-carrier extraction between the ETL and the perovskite layer. Consequently, the PSC with BH modification yields a higher PCE, a lower hysteresis, and better stability than the device without a BH interlayer. This study highlights the key role of molecule modification of ETLs in designing efficient and stable PSCs.

Modifying SnO2 with Polyacrylamide to Enhance the Performance of Perovskite Solar Cells

Modification of the charge transport layers is an effective way to improve charge transport and performance of perovskite solar cells (PSCs). The ions in the ionic compounds used for the modification of SnO2 may migrate into the perovskite layer, which harms the stability of PSCs. In this work, a low-cost, water-soluble nonionic polymer polyacrylamide (PAM) is used to modify SnO2. The addition of PAM improves the uniformity, wettability, and electron mobility of the SnO2 film. Through the modification of SnO2, the defects of perovskite films are reduced and the grain size is increased. Furthermore, the energy-level alignment at the SnO2/perovskite interface is improved, which is beneficial to the transfer of electrons from perovskite to SnO2. Finally, the power conversion efficiency (PCE) of PSCs formed from modified SnO2 is enhanced to 22.59%. More importantly, the unencapsulated devices with modified SnO2 retain 90% of the initial value after storage for more than 1000 h under a relative humidity of 50%. These results indicate that modifying SnO2 using PAM is a promising strategy to improve the performance of PSCs.

Interfacial Dipole poly(2-ethyl-2-oxazoline) Modification Triggers Simultaneous Band Alignment and Passivation for Air-Stable Perovskite Solar Cells

To promote the performance of perovskite solar cells (PSCs), its theoretical power conversion efficiency (PCE) and high stability, elaborative defect passivation, and interfacial engineering at the molecular level are required to regulate the optoelectric properties and charge transporting process at the perovskite/hole transport layer (HTL) interfaces. Herein, we introduce for the first time a multifunctional dipole polymer poly(2-ethyl-2-oxazoline) (PEOz) between the perovskite and Spiro-OMeTAD HTL in planar n-i-p PSCs, which advances the PSCs toward both high efficiency and excellent stability by stimulating three beneficial effects. First, the ether–oxygen unshared electron pairs in PEOz chemically react with unsaturated Pb²⁺ on the perovskite surfaces by forming a strong Pb–O bond, which effectively reduces the uncoordinated defects on the perovskite surfaces and enhances the absorption ability of the resulting PSCs. Second, the dipole induced by PEOz at the perovskite/HTL interface can decrease the HOMO and LUMO level of Spiro-OMeTAD and optimize the band alignment between these layers, thereby suppressing the interfacial recombination and accelerating the hole transport/extraction ability in the cell. Third, the hygroscopic PEOz thin film can protect perovskite film from water erosion by absorbing the water molecules before perovskite does. Finally, the PEOz-modified PSC exhibits an optimized PCE of 21.86%, with a high short-circuit current density (Jsc) of 24.88 mA/cm², a fill factor (FF) of 0.79, and an open-circuit voltage (Voc) of 1.11 V. The unencapsulated devices also deliver excellent operation stability over 300 h in an ambient atmosphere with a humidity of 30~40% and more than 10 h under thermal stress.

Record-Efficiency Flexible Perovskite Solar Cells Enabled by Multifunctional Organic Ions Interface Passivation

Flexible perovskite solar cells (f-PSCs) have attracted great attention because of their unique advantages in lightweight and portable electronics applications. However, their efficiencies are far inferior to those of their rigid counterparts. Herein, a novel histamine diiodate (HADI) is designed based on theoretical study to modify the SnO₂ /perovskite interface. Systematic experimental results reveal that the HADI serves effectively as a multifunctional agent mainly in three aspects: 1) surface modification to realign the SnO₂ conduction band upward to improve interfacial charge extraction; 2) passivating the buried perovskite surface, and 3) bridging between the SnO₂ and perovskite layers for effective charge transfer. Consequently, the rigid MA-free PSCs based on the HADI-SnO₂ electron transport layer (ETL) display not only a high champion power conversion efficiency (PCE) of 24.79% and open-circuit voltage (V_OC ) of 1.20 V but also outstanding stability as demonstrated by the PSCs preserving 91% of their initial efficiencies after being exposed to ambient atmosphere for 1200 h without any encapsulation. Furthermore, the solution-processed HADI-SnO₂ ETL formed at low temperature (100 °C) is utilized in f-PSCs that achieve a PCE as high as 22.44%, the highest reported PCE for f-PSCs to date.

Embedding SnO2 Thin Shell Protected Ag Nanowires in SnO2 ETL to Enhance the Performance of Perovskite Solar Cells

The energy level mismatching between SnO₂ and perovskite and the nonradiative recombination at SnO₂-perovskite interface severely degrade the extraction of carriers, reducing the power conversion efficiency (PCE) and stability of planar perovskite solar cells (PSCs) based on SnO₂ electron transfer layer (ETL). In the present work, a reinforced SnO₂ ETL was successfully developed by embedding SnO₂ thin shell protected Ag nanowires (Ag/SnO₂ NWs) in traditional planar SnO₂ film, which was proved to not only lower the conduction band of SnO₂ to adjust the energy level matching, but also significantly reduce the interfacial carrier recombination. Moreover, Ag/SnO₂ NWs improved the electrical conductivity of SnO₂ ETL, and effectively promoted carrier transport. Benefiting from the use of Ag/SnO₂ NWs, our newly designed PSC achieved a significantly increased champion PCE of 19.78%, which is 7% higher than the traditional PSC without Ag/SnO₂ NWs embedding, indicating its great application potential in PSCs.

Conversion of Interfacial Chemical Bonds for Inducing Efficient Photoelectrocatalytic Water Splitting

Sp-C-hybridized alkyne bonds present the natural advantages of interacting with metal atoms and have the ability to generate a large number of new catalytic active sites on the surface and the interfaces, thus greatly promoting the efficient progress of various light/electrochemical reactions. In this work, we have successfully fabricated a novel type of interfacial structure containing sp-C-Mo/O bonds and mixed Mo valence states with outstanding catalytic activity and stability for photoelectrocatalytic (PEC) overall water splitting in a wide pH range (0-14), due to the presence of sp-carbon-rich graphdiyne. For example, in alkaline conditions (pH = 14), the overpotentials of oxygen and hydrogen evolution reactions at 10 mA cm-2 are 165 and 8 mV. When being used as an electrolyzer, the cell voltage of this catalyst is only 1.40 V to achieve 10 mA cm-2. The high PEC activity of graphdiyne@molybdenum oxide originates from the conversion of chemical bonds at the sp-C hybrid interface and the coexistence of multivalent states of molybdenum, triggering a large number of catalytic active sites, greatly promoting charge transfer and lowering water dissociation energy.

Reciprocally Photovoltaic Light-Emitting Diode Based on Dispersive Perovskite Nanocrystal

Integrating highly efficient photovoltaic (PV) function into light-emitting diodes (LEDs) for multifunctional display is of great significance for compact low-power electronics, but it remains challenging. Herein, it is demonstrated that solution engineered perovskite nanocrystals (PNCs, ≈100 nm) enable efficient electroluminescence (EL) and PV performance within a single device through tailoring the dispersity and interface. It delivers the maximum brightness of 490 W sr^-1  m^-2 at 2.7 V and 23.2% EL external quantum efficiency, a record value for near-infrared perovskite LED, as well as 15.23% PV efficiency, among the highest value for nanocrystal perovskite solar cells. The PV-EL performance is well in line with the reciprocity relation. These all-solution-processed PV-LED devices open up viable routes to a variety of advanced applications, from touchless interactive screens to energy harvesting displays and data communication.

Boosting room-temperature ppb-level NO2 sensing over reduced graphene oxide by co-decoration of α-Fe2O3 and SnO2 nanocrystals

As promising sensing materials, reduced graphene oxide (RGO)-based nanomaterials have drawn considerable attention in the fields of gas monitoring owing to their low operating temperature. However, constructing RGO-based room-temperature gas sensors possessing ppb-level limit of detection with high sensitivity remains challenging. In this work, a series of highly sensitive NO₂ sensors were fabricated using α-Fe₂O₃ and SnO₂ co-decorated RGO hybrids (designated as α-Fe₂O₃/SnO₂-RGO) as sensing materials. They were rationally synthesized by a one-pot hydrothermal method. Compared to SnO₂ modified RGO hybrids (SnO₂-RGO with bandgap of 3.88 eV), the bandgap energy of α-Fe₂O₃/SnO₂-RGO hybrids (3.53 eV) was reduced by adding α-Fe₂O_3; the narrower bandgap facilitated the sensing materials to release more electrons and form more oxygen ions at room temperature. Besides, the high carrier migration of RGO, which served as continuous phase, identical structure with ultrasmall particle size of α-Fe₂O₃ and SnO₂ (about 3-6 nm), and abundant chemisorbed oxygen species on the surface (20.8%) of the sensing materials, as well as their suitable bandgap (3.53 eV) in the sensing materials, significantly improved NO₂ response at room temperature. Among the sensors fabricated, α-Fe₂O₃/SnO₂-RGO-15-based NO₂ sensor had the highest response of 7.4 with a short response time of 59 s towards 1 ppm NO₂; it could even reach a response of 2.6 towards 100 ppb NO₂. Notably, α-Fe₂O₃/SnO₂-RGO-15 sample has excellent capability to recognize NO₂, where the response value (7.4) towards 1 ppm NO₂ is about 7 times higher than that of 100 ppm ammonia and common volatile organic compounds (formaldehyde, toluene, ethanol and acetone). Such NO₂ sensor has superior repeatability with negligible response deviation towards 1 ppm NO₂ for four reversible cycles. This makes it to have a great potential application in the field of NO₂ detection.

Interpretation of Rubidium-Based Perovskite Recipes toward Electronic Passivation and Ion-Diffusion Mitigation

Rubidium cation (Rb⁺ ) addition is witnessed to play a pivotal role in boosting the comprehensive performance of organic-inorganic hybrid perovskite solar cells. However, the origin of such success derived from irreplaceable superiorities brought by Rb⁺ remains ambiguous. Herein, grain-boundary-including atomic models are adopted for the accurate theoretical analysis of practical Rb⁺ distribution in perovskite structures. The spatial distribution, covering both the grain interiors and boundaries, is thoroughly identified by virtue of synchrotron-based grazing-incidence X-ray diffraction. On this basis, the prominent elevation of the halogen vacancy formation energy, improved charge-carrier dynamics, and the electronic passivation mechanism in the grain interior are expounded. As evidenced by the increased energy barrier and suppressed microcurrent, the critical role of Rb⁺ addition in blocking the diffusion pathway along grain boundaries, inhibiting halide phase segregation, and eventually enhancing intrinsic stability is elucidated. Hence, the linkage avalanche effect of occupied location dominated by subtle changes in Rb⁺ concentration on electronic defects, ion migration, and phase stability is completely investigated in detail, shedding a new light on the advancement of high-efficiency cascade-incorporating strategies and perovskite compositional engineering.