Ultralong Carrier Lifetime Exceeding 20 µs in Lead Halide Perovskite Film Enable Efficient Solar Cells

Bandgap-Tunable Halide Perovskite Quantum Dots Enabled by Femtosecond Laser Patterning for Full-Color and High-Resolution Display

Perovskite quantum dots (PQDs) have garnered significant attention for their exceptional optoelectronic properties, yet achieving precise luminescence control often involves complex chemical processes, and traditional display technologies face material and environmental limitations. In this study, we present an innovative approach utilizing three distinct halide perovskite quantum dot solutions to achieve tunable emission properties without additional chemical modifications. By employing femtosecond laser patterning, we successfully fabricated high-resolution (1.5 μm spacing), full-color (410-710 nm) quantum dot patterns with excellent environmental stability. This method eliminates the need for excessive chemical reagents and intricate masking steps, significantly streamlining the fabrication process and enhancing efficiency. Our findings highlight the potential of combining bandgap engineering with advanced patterning techniques, offering a practical foundation for green synthesis and simplified manufacturing processes in next-generation display technologies.

Synergistic Effect of Cation and Anion Passivation Defects and Suppression of Phase Transition Enhance the Performance and Stability of Inverted Perovskite Solar Cells

The trap states and phase instability of perovskite films harm the fabrication of high-performance and stable perovskite solar cells (PSCs). Herein, the β-fluorophenylethanammonium cation (β-FPEA+) and tosylate anions (TsO-) are employed to enhance both the performance and stability of inverted PSCs. Theoretical calculations show that β-FPEA+TsO- can passivate the defects at both FA-I and Pb-I terminals. Nuclear magnetic resonance reveals strong interactions between β-FPEA+TsO- and perovskites, which facilitate the fabrication of high-quality perovskite films. During crystallization, β-FPEA+ preferentially generates the 2D perovskite, stabilizing the black phase and passivating defects of the perovskite film. Meanwhile, the large TsO- can be extruded to the grain boundary and surface, reducing trap states and inhibiting the degradation of the perovskite film. The synergistic effect of β-FPEA+ and TsO- passivation on defects and suppression of phase transition results in the power conversion efficiency (PCE) improved to 25.47% (vs 23.08% of the control), along with the unencapsulated device retaining 81% of initial PCE after 960 h at 85 °C in vacuum. This work provides a novel and simple strategy for designing the combination of large organic cations and non-halogenated anions to passivate the defects and suppress phase transition, thereby achieving high performance and stable PSCs.

Semiconductor Spacer with Donor-Acceptor Structure Drives 2D Ruddlesden-Popper Perovskite Solar Cells Beyond 20% Efficiency

Two dimensional (2D) Ruddlesden-Popper (RP) perovskites have emerged as promising photovoltaic materials. However, their further improvement in photovoltaic efficiency is hindered by the large dielectric mismatch and high exciton binding energy caused by the insulating spacers. Herein, two semiconductor spacers, namely MeBThMA and CNBThMA, were developed for 2D RP perovskite solar cells (PSCs). In contrast to MeBThMA, the CNBThMA spacer, which features a donor-acceptor (D-A) structure, exhibits a larger dipole moment and adopts a face-to-face molecular stacking arrangement in the single crystal. The unique D-A structure effectively eliminates the dielectric mismatch between the organic and inorganic layers, contributing the formation of energy levels, adjusting the anisotropic charge transport properties, and improving the film quality of layered RP perovskites. Consequently, the devices based on CNBThMA (nominal n = 5) achieved a champion efficiency of 20.82%, which is a record efficiency for 2D RP PSCs using semiconductor spacers to the best of our knowledge. Our work pioneers a novel way to design organic semiconductor spacers using a D-A structure for highly efficient 2D PSCs.

2D/3D Heterojunction Engineering for Hole Transport Layer-Free Carbon-Based Perovskite Solar Cells

Hole transport layer (HTL)-free carbon-based perovskite solar cells (C-PSCs) own outstanding potential for commercial applications due to their attractive advantages of low cost and superior stability. However, the abundant defects and mismatched energy levels at the interface of the perovskite/carbon electrode severely limit the device efficiency and stability. Constructing a 2D layer on the surface of 3D perovskite films to form 2D/3D heterojunctions has been demonstrated to be an effective method of passivating surface defects and optimizing the energy level alignment in almost all kinds of PSCs. Due to the unique structure of HTL-free C-PSCs, 2D/3D heterojunctions play especially important roles. This review article summarizes the reports of 2D/3D perovskite heterojunctions in HTL-free C-PSCs. It describes the contributions of 2D/3D heterojunctions in terms of their roles in defect passivation, energy level optimization, and stability improvement. Finally, challenges and prospects of 2D/3D heterojunction for further development of HTL-free C-PSCs are highlighted.

Low-Dimensional Ligand-Driven Design of 2D/3D Perovskite Heterojunctions: Achieving Mitigated Nonradiative Recombination and Robust Stability for Next-Generation Solar Cells

Achieving efficient and stable perovskite solar cells (PSCs) is challenging due to nonradiative recombination, ion migration, and film instability. This study designs low-dimensional (LD) ligands─benzimidazole (BIZ), 1H-benzimidazole, 6-methyl-, (6-MeBIm), and 1H-benzimidazole, 6-(trifluoromethyl)-, (6-TFBIm)─to construct LD/3D perovskite heterojunctions. Compared with BIZ and 6-MeBIm (constructing 1D/3D perovskite heterojunction), the 2D/3D perovskite heterojunction constructed by 6-TFBIm successfully passivated different defects, resulting in a significant reduction in nonradiative recombination and improved carrier transport, leading to a power conversion efficiency (PCE) of 25.25%, outperforming the control devices (PCE: 22.97%). The 2D/3D PSCs exhibit superior humidity and thermal stability, maintaining structural integrity under harsh conditions. These results underscore the role of tailored LD ligands in optimizing perovskite film quality, charge transport, and stability, paving the way for high-performance and durable PSCs.

Carboxyl-Functionalized Sulfonium Additive for Improved Crystallization and Defect Passivation in Ternary Cation Perovskite Solar Cells

This study explores the use of 2-(carboxyethyl) (dimethyl)sulfonium bromide (CDMSBr), a carboxyl-functionalized derivative of trimethylsulfonium (TMS+), as an additive in ternary cation, (Cs0.05FA0.90MA0.05Pb(I0.95Br0.05)3 [CsFAMA]), perovskite solar cells (PSCs) to enhance both stability and photovoltaic performance. In solution, it exhibits a zwitterionic form that controls nucleation and growth of perovskite crystals. It further protonates into CDMS+ during crystallization to facilitate the formation of larger and more uniform grains with better crystallinity. Optimized CsFAMA-based device achieves power conversion efficiency (PCE) of 21.02% (enhancement of 6.54%) at 1-sun condition and 38.79% (enhancement of 9.21%) under low-intensity indoor lighting (1000-lx, LED 5000 K). The dual role of the additive in defect passivation and grain size enhancement contributes to reduced trap density, promoting increased stability of the PSCs. Devices with CDMSBr maintain 88.53% of their initial PCE after 960 h in ambient conditions. These findings highlight the potential of carboxyl-functionalized sulfonium additives, like CDMSBr, to enhance perovskite morphology and stability, advancing the performance and operational durability of PSCs.

Precise Control of Lead Halide and Ammonium Salt Stoichiometric Ratios for Efficient Perovskite Solar Cells

The precise stoichiometric ratio of lead halide and organic ammonium salts is a fundamental yet unresolved scientific challenge in perovskite solar cells (PSCs). Conventional deposition techniques fail to establish a definitive structure-performance relationship due to limitations in quantitative control, leading to inconsistent film quality and ambiguous reaction pathways. In this work, a precise quantitative deposition approach using drop-on-demand inkjet printing to systematically investigate the impact of organic salt deposition surface density on PSC performance is developed. The findings reveal that the deposition amount significantly affects the morphology, composition, and crystallinity of the perovskite films, influencing the overall device performance. Low deposition surface densities below 22 µg cm-2 produce thin perovskite films with incomplete crystallization and small crystals, hindering charge carrier transport and separation. Conversely, a high deposition density (89 µg cm-2) results in over-reaction between the organic salt and PbI2, leading to low-quality perovskite films with pinholes, cracks, and poor interfacial contact. At the optimal deposition density of 39 µg cm-2, it achieves high-quality perovskite films with large grains, reduced defects, and improved energy level alignment, resulting in a champion efficiency of 23.3% and improved environmental stability for the devices.

Decoding recombination dynamics in perovskite solar cells: an in-depth critical review

The remarkable optoelectronic properties of metal halide perovskites (MHPs) have established them as highly promising photovoltaic absorber materials, propelling the rapid advancement of perovskite solar cells (PSCs) that outperform many traditional alternatives in terms of power conversion efficiency (PCE). However, despite their advancements, PSC devices encounter significant non-radiative recombination losses, encompassing trap-assisted (Shockley-Read-Hall) recombination in bulk and interfaces of PSCs, which restricts their open-circuit voltage (VOC) and overall PCE, dragging it below the Shockley-Queisser (SQ) limit. The ongoing debate regarding the role of grain boundary (GB) recombination, whether it primarily manifests as bulk or surface recombination, has spurred extensive research aimed at elucidating these mechanisms. This review provides a critical comprehensive analysis of the thermodynamic correlations related to VOC losses, bridging the gap between the theoretical SQ limit and practical device performance. Subsequently, it delves into recent findings that aim to decipher the multifaced nature and origin of radiative and non-radiative recombination-induced losses within the device stack, assessing their impacts on overall performance. Furthermore, this review emphasizes the application of advanced machine learning techniques to discern dominant recombination mechanisms in PSCs. Finally, it summarizes the notable advanced strategies to mitigate undesirable non-radiative recombination losses, which pave the way to the thermodynamic efficiency limit.

Quantum Batteries: A Materials Science Perspective

In the context of quantum thermodynamics, quantum batteries have emerged as promising devices for energy storage and manipulation. Over the past decade, substantial progress is made in understanding the fundamental properties of quantum batteries, with several experimental implementations showing great promise. This perspective provides an overview of the solid-state materials platforms that can lead to fully operational quantum batteries. After briefly introducing the basic features of quantum batteries, organic microcavities are discussed, where superextensive charging is already demonstrated experimentally. Now, this explores other materials, including inorganic nanostructures (such as quantum wells and dots), perovskite systems, and (normal and high-temperature) superconductors. Key achievements in these areas, relevant to the experimental realization of quantum batteries, are highlighted. The challenges and future research directions are also addressed. Despite their enormous potential for energy storage devices, research into advanced materials for quantum batteries is still in its infancy. This paper aims to stimulate interdisciplinarity and convergence among different materials science research communities to accelerate the development of new materials and device architectures for quantum batteries.

Real-space imaging of photo-generated surface carrier transport in 2D perovskites

In layered two-dimensional (2D) perovskites, the inorganic perovskite layers sandwiched between cation spacers create quantum well (QW) structures, showing large exciton binding energies that hinder the efficient dissociation of excitons into free carriers. This leads to poor carrier transport properties and low-performance light-conversion-based devices, and the direct understanding of the underlying physics, particularly concerning surface states, remains extremely difficult, if not impossible, due to the challenges in real-time accessibility. Here, we utilized four-dimensional scanning ultrafast electron microscopy (4D-SUEM), a highly sensitive technique for mapping surface carrier diffusion that diverges from those in the bulk and substantially affects material properties. We directly visualize photo-generated carrier transport over both spatial and temporal dimensions on the top surface of 2D perovskites with varying inorganic perovskite layer thicknesses (n = 1, 2, and 3). The results reveal the photo-induced surface carrier diffusion rates of ~30 cm2·s-1 for n = 1, ~180 cm2·s-1 for n = 2, and ~470 cm2·s-1 for n = 3, which are over 20 times larger than bulk. This is because charge carrier transmission channels have much wider distributions on the top surface compared to the bulk, as supported by the Density Functional Theory (DFT) calculations. Finally, our findings represent the demonstration to directly correlate the discrepancies between surface and bulk carrier diffusion behaviors, their relationship with exciton binding energy, and the number of layers in 2D perovskites, providing valuable insights into enhancing the performance of 2D perovskite-based optoelectronic devices through interface engineering.

Defect Passivation and Stress Release Strategies for Inverted Perovskite Solar Cells Based on the Low-Pressure-Assisted Solution Process

Perovskite solar cells (PSCs) have attracted much attention in the global photovoltaic field due to their excellent optoelectronic properties. However, the intrinsic crystalline properties and the preparation methods of perovskites result in numerous defects and residual stress in the perovskite film. To address this issue, the additive 3-methylthio-1-propylammonium bromide (3MeSPABr) was added to the perovskite precursor solution, and PSCs with an inverted structure via a low-pressure-assisted solution process were fabricated. The additive was found to interact with the perovskite through strong coordination and hydrogen bonding, passivate defects, and alleviate residual tensile stress. The power conversion efficiency (PCE) of the PSCs as high as 21.99% was obtained. Besides, the addition of 3MeSPABr also increases the hydrophobicity of the perovskite film and improves the stability of the PSCs.

Ultrafast Carrier Diffusion in Perovskite Monocrystalline Films

Monocrystalline perovskite materials exhibit superior properties compared with polycrystalline perovskites, including lower defect density, minimal grain boundaries, and enhanced carrier mobility. Nevertheless, the preparation of large-area, high-quality single-crystal films, which could prove invaluable for photoelectronic applications, remains a significant challenge. The study of how their unique properties go beyond polycrystalline thin films is still missing. In our experiment, using polarization-selective transient absorption microscopy, we directly observed the spatial carrier transportation in methylammonium lead iodide (CH3NH3PbI3, MAPbI3) strip-shaped monocrystalline ultrathin films. Ultrafast carrier diffusion transportation was observed. The monocrystalline carrier diffusion coefficient D (∼22 cm2 s-1) is an order of magnitude higher than that in polycrystalline films. Anisotropic carrier diffusion of the MAPbI3 single crystal has been discovered. It is also discovered that the electrons and holes are of different anisotropy and diffusion speed. This ultralong carrier transport inside the monocrystalline film provides solid support for the development of perovskite based photoelectronic devices.

Unveiling Energy Conversion Mechanisms and Regulation Strategies in Perovskite Solar Cells

Despite recent revolutionary advancements in photovoltaic (PV) technology, further improving cell efficiencies toward their Shockley-Queisser (SQ) limits remains challenging due to inherent optical, electrical, and thermal losses. Currently, most research focuses on improving optical and electrical performance through maximizing spectral utilization and suppressing carrier recombination losses, while there is a serious lack of effective opto-electro-thermal coupled management, which, however, is crucial for further improving PV performance and the practical application of PV devices. In this article, the energy conversion and loss processes of a PV device (with a specific focus on perovskite solar cells) are detailed under both steady-state and transient processes through rigorous opto-electro-thermal coupling simulation. By innovatively coupling multi-physical behaviors of photon management, carrier/ion transport, and thermodynamics, it meticulously quantifies and analyzes energy losses across optical, electrical, and thermal domains, identifies heat components amenable to regulation, and proposes specific regulatory means, evaluates their impact on device efficiency and operating temperature, offering valuable insights to advance PV technology for practical applications.

Neutral Ligand Triggered Low-Dimensional Reconstruction for Improving the Efficiency and Stability of Perovskite Solar Cells

Perovskite solar cells (PSCs) offer a potentially large-scale method for producing low-cost renewable energy. However, stability challenges currently limit their practical application. Consequently, alternative methods for increasing the PSC stability are urgently needed. Compared with three-dimensional (3D) perovskites, low-dimensional (LD) perovskites have been shown to have higher stability. In this study, a LD/3D hybrid perovskite strategy is used that involves post-treating the Cs0.05(FA0.98MA0.02)0.95Pb(I0.98Br0.02)3 perovskite with a neutral allyl 1H-imidazole-1-carboxylate (AImC) ligand. We show that this neutral organic spacer molecule has two key roles. AImC acts as a solvent and triggers localized reconstruction to produce a LD capping layer in one postprocessing step. AImC prolongs the carrier lifetime and reduces trap-assisted recombination. As a result, the PSCs containing AImC achieve a maximum power conversion efficiency (PCE) of 21.42% compared to 20.27% for the control device and show significantly decreased hysteresis. AImC also greatly increased the stability of the films and devices to air, moisture, and heat. The results of this study imply that neutral amine liquids that have the correct solvating and ligating properties have good potential to improve the PCE and stability of the PSCs.

Fabrication of Efficient and Simple-Structured Perovskite Solar Cells Using a Multifunctional Biocolina Surface Treatment

The electron transport layer (ETL)-free perovskite solar cells (PSCs) have gained significant interest by simplifying the manufacture process and reducing the time/energy required for the fabrication of ETLs. Unfortunately, the performance of these ETL-free PSCs still lags behind those of the conventional counterparts due to the slow electron extraction and undesired interfacial charge recombination loss at the buried interface. In this work, a facile and multifunctional biocolina thin layer is incorporated on the bottom electrodes to regulate the interface energy level alignment by forming an interface dipole layer, resulting in a suppressed nonradiative recombination and an improved charge extraction. Furthermore, the biocolina thin layer possess the capability to passivate the surface defects within the perovskite films while simultaneously facilitate the formation of perovskite crystals. Consequently, a remarkable enhancement in photovoltaic performance is observed in the biocolina-based ETL-free PSCs with an increase from 15.96 % to an outstanding 20.01 %. Additionally, the biocolina extends the stability and relieves the hysteresis effect through the interface defect passivation and inhibition of interface charge accumulation. This research contributes to the development of cost-effective, simplified designs for highly efficient ETL-free PSCs by modifying the bottom electrodes.

Impurity-healing interface engineering for efficient perovskite submodules

An issue that affects the scaling-up development of perovskite photovoltaics is the marked efficiency drop when enlarging the device area, caused by the inhomogeneous distribution of defected sites1-3. In the narrow band gap formamidinium lead iodide (FAPbI3), the native impurities of PbI2 and δ-FAPbI3 non-perovskite could induce unfavoured non-radiative recombination, as well as inferior charge transport and extraction4,5. Here we develop an impurity-healing interface engineering strategy to address the issue in small-area solar cells and large-scale submodules. With the introduction of a functional cation, 2-(1-cyclohexenyl)ethyl ammonium, two-dimensional perovskite with high mobility is rationally constructed on FAPbI3 to horizontally cover the film surface and to vertically penetrate the grain boundaries of three-dimensional perovskites. This unique configuration not only comprehensively transforms the PbI2 and δ-FAPbI3 impurities into stable two-dimensional perovskite and realizes uniform defect passivation but also provides interconnecting channels for efficient carrier transport. As a result, the FAPbI3-based small-area (0.085 cm2) solar cells achieve a champion efficiency of more than 25.86% with a notably high fill factor of 86.16%. The fabricated submodules with an aperture area of 715.1 cm2 obtain a certified record efficiency of 22.46% with a good fill factor of 81.21%, showcasing the feasibility and effectualness of the impurity-healing interface engineering for scaling-up promotion with well-preserved photovoltaic performance.

Controlled Nucleation and Oriented Crystallization of Methylammonium-Free Perovskites via In Situ Generated 2D Perovskite Phases

Enhancing stability while maintaining high efficiency is among the primary challenges in the commercialization of perovskite solar cells (PSCs). Here, a crystal growth technique assisted by in situ generated 2D perovskite phases has been developed to construct high-quality 2D/3D perovskite films. The in situ generated 2D perovskite serve as templates for regulating the nucleation and oriented crystal growth in the α-FAPbI3-rich film. This led to a high film quality with much reduced trap density and an ultralong carrier lifetime. The obtained perovskite film shows excellent stability under extreme environment conditions (T = 200 °C, RH = 75 ± 5%). The corresponding PSC achieved an efficiency of 26.16% (certified 25.84%), along with excellent operational stability (T93 > 1300 h, T ≅ 50 °C) as well as outstanding high and low temperature cycle stability.

Advances in Mixed Tin-Lead Narrow-Bandgap Perovskites for Single-Junction and All-Perovskite Tandem Solar Cells

Organic-inorganic metal-halide perovskites have received great attention for photovoltaic (PV) applications owing to their superior optoelectronic properties and the unprecedented performance development. For single-junction PV devices, although lead (Pb)-based perovskite solar cells have achieved 26.1% efficiency, the mixed tin-lead (Sn-Pb) perovskites offer more ideal bandgap tuning capability to enable an even higher performance. The Sn-Pb perovskite (with a bandgap tuned to ≈1.2 eV) is also attractive as the bottom subcell for a tandem configuration to further surpass the Shockley-Queisser radiative limit for the single-junction devices. The performance of the all-perovskite tandem solar cells has gained rapid development and achieved a certified efficiency up to 29.1%. In this article, the properties and recent development of state-of-the-art mixed Sn-Pb perovskites and their application in single-junction and all-perovskite tandem solar cells are reviewed. Recent advances in various approaches covering additives, solvents, interfaces, and perovskite growth are highlighted. The authors also provide the perspective and outlook on the challenges and strategies for further development of mixed Sn-Pb perovskites in both efficiency and stability for PV applications.

Band alignment engineering of 2D/3D halide perovskite lateral heterostructures

Two-dimensional (2D)/three-dimensional (3D) halide perovskite heterostructures have been extensively studied for their ability to combine the outstanding long-term stability of 2D perovskites with the superb optoelectronic properties of 3D perovskites. While current studies mostly focus on vertically stacked 2D/3D perovskite heterostructures, a theoretical understanding regarding the optoelectronic properties of 2D/3D perovskite lateral heterostructures is still lacking. Herein, we construct a series of 2D/3D perovskite lateral heterostructures to study their optoelectronic properties and interfacial charge transfer using density functional theory (DFT) calculations. We find that the band alignments of 2D/3D heterostructures can be regulated by varying the quantum-well thickness of 2D perovskites. Moreover, decreasing the 2D component ratio in 2D/3D heterostructures can be favorable to form type-I band alignment, whereas a large component ratio of 2D perovskites tends to form type-II band alignment. We can improve the amount of charge transfer at the 2D/3D perovskite interfaces and the light absorption of 2D perovskites by increasing quantum-well thickness. These present findings can provide a clear designing principle for achieving 3D/2D perovskite lateral heterostructures with tunable optoelectronic properties.

Stable FAPbI3 Perovskite Solar Cells via Alkylammonium Chloride-Mediated Crystallization Control

α-Phase formamidinium lead iodide (FAPbI3) perovskite solar cells (PSCs) have garnered significant attention, owing to their remarkable efficiency. Methylammonium chloride (MACl), a common additive, is used to control the crystallization of FAPbI3, thereby facilitating the formation of the photoactive α-phase. However, MACl's high volatility raises concerns regarding its stability and potential impact on the stability of the device. In this study, we partially substituted MACl with n-propylammonium chloride (PACl), which has a long alkyl chain, to promote the oriented crystallization of FAPbI3, ultimately forming an δ-phase-free perovskite. The FAPbI3 film containing PACl demonstrates an enhanced photoluminescence intensity and lifetime. Additionally, PACl's presence at grain boundaries acts as a protective layer for the PSCs. Consequently, we achieved a power conversion efficiency (PCE) of 22.4% and exceptional stability. It maintains over 95% of initial PCE for 100 days in an N2 glovebox, over 85% after 100 h of maximum power point tracking, and over 80% after 60 °C thermal aging.

Vacuum-Processed Propylene Urea Additive: A Novel Approach for Controlling the Growth of CH3NH3PbI3 Crystals in All Vacuum-Processed Perovskite Solar Cells

In this study, we present a novel method for controlling the growth of perovskite crystals in the vacuum thermal evaporation process by utilizing a vacuum-processable additive, propylene urea (PU). By coevaporation of perovskite precursors with PU to form the perovskite layer, PU, acting as a Lewis base additive, retards the direct reaction between the perovskite precursors. This facilitates a larger domain size and reduced defect density. Following the removal of the residual additive, the perovskite layer, exhibiting improved crystallinity, demonstrates reduced charge recombination, as confirmed by a time-resolved microwave conductivity analysis. Consequently, there is a notable enhancement in open-circuit voltage and power conversion efficiency, increasing from 1.05 to 1.15 V and from 17.17 to 18.31%, respectively. The incorporation of a vacuum-processable and removable Lewis base additive into the fabrication of vacuum-processed perovskite solar cells offers new avenues for optimizing these devices.

Multi-Functional Spirobifluorene Phosphonate Based Exciplex Interface Enables Voc Reaching 95% of Theoretical Limit for Perovskite Solar Cells

Metal halide perovskite solar cells (PSCs) show significant advancements in power conversion efficiency (PCE). However, the open-circuit voltage (VOC) of PSCs is limited by interfacial factors such as defect-induced recombination, energy band mismatch, and non-intimate interface contact. Here, an exciplex interface is first developed based on the strategically designed and synthesized two spirobifluorene phosphonate molecules to mitigate VOC loss in PSCs. The exciplex interface constructed by the intimate contact between the multi-functional molecules and hole transport layer takes the roles to promote the hole extraction by donor-acceptor interaction, passivate coordination-unsaturated Pb2+ defects by equipped phosphonate groups, and optimize the energy level alignment. As a result, a record VOC of 1.26 V with a perovskite bandgap of 1.61 eV is achieved, representing over 95% of theoretical limit. This advancement leads to an increase in PCE from 21.29% to 24.12% and improved stability. The exciplex interface paves the way for addressing the long-standing challenge of VOC loss and promotes the wider application of PSCs.

Modulating Dimensionality of 2D Perovskite Layers for Efficient and Stable 2D/3D Perovskite Photodetectors

Two-dimensional (2D) perovskites have been widely adopted for improving the performance and stability of three-dimensional (3D) metal halide perovskite devices. However, rational manipulation of the phase composition of 2D perovskites for suitable energy level alignment in 2D/3D perovskite photodetectors (PDs) has been rarely explored. Herein, we precisely controlled the dimensionality of the 2D perovskite on CsPbI2Br films by tuning the polarity of the n-butylammonium iodide (BAI)-based solvents. In comparison to the pure n = 1 2D perovskite (ACN-BAI) formed by acetonitrile treatment, a mixture of n = 1 and n = 2 phases (IPA-BAI) generated by isopropanol (IPA) treatment guaranteed more robust defect passivation and favorable energy level alignment at the perovskite/hole transport layer interface. Consequently, the IPA-BAI PD exhibited a responsivity of 0.41 A W-1, a detectivity of 1.01 × 1013 Jones, and a linear dynamic range of 120 dB. Furthermore, the mixed-phase 2D layer effectively shielded the 3D perovskite from moisture. The IPA-BAI device retained 76% of its initial responsivity after 500 h of nonencapsulated storage at 10% relative humidity. This research provides valuable insights into the dimensional modulation of 2D perovskites for further enhancing the performance of 2D/3D perovskite PDs.

Dimensional Regulation from 1D/3D to 2D/3D of Perovskite Interfaces for Stable Inverted Perovskite Solar Cells

Constructing low-dimensional/three-dimensional (LD/3D) perovskite solar cells can improve efficiency and stability. However, the design and selection of LD perovskite capping materials are incredibly scarce for inverted perovskite solar cells (PSCs) because LD perovskite capping layers often favor hole extraction and impede electron extraction. Here, we develop a facile and effective strategy to modify the perovskite surface by passivating the surface defects and modulating surface electrical properties by incorporating morpholine hydriodide (MORI) and thiomorpholine hydriodide (SMORI) on the perovskite surface. Compared with the PI treatment that we previously developed, the one-dimensional (1D) perovskite capping layer derived from PI is transformed into a two-dimensional (2D) perovskite capping layer (with MORI or SMORI), achieving dimension regulation. It is shown that the 2D SMORI perovskite capping layer induces more robust surface passivation and stronger n-N homotype 2D/3D heterojunctions, achieving a p-i-n inverted solar cell with an efficiency of 24.55%, which retains 87.6% of its initial efficiency after 1500 h of operation at the maximum power point (MPP). Furthermore, 5 × 5 cm2 perovskite mini-modules are presented, achieving an active-area efficiency of 22.28%. In addition, the quantum well structure in the 2D perovskite capping layer increases the moisture resistance, suppresses ion migration, and improves PSCs' structural and environmental stability.

High Q-Factor Single-Mode Lasing in Inorganic Perovskite Microcavities with Microfocusing Field Confinement

The realization of high-Q single-mode lasing on the microscale is significant for the advancement of on-chip integrated light sources. It remains a challenging trade-off between Q-factor enhancement and light-field localization to raise the lasing emission rate. Here, we fabricated a zero-dimensional perovskite microcavity integrated with a nondamage pressed microlens to three-dimensionally tailor the intracavity light field and demonstrated linearly and nonlinearly (two-photon) pumped lasing by this microfocusing configuration. Notably, the microlensing microcavity experimentally achieves a high Q-factor (16700), high polarization (99.6%), and high Purcell factor (11.40) single-mode lasing under high-repetition pulse pumping. Three-dimensional light-field confinement formed by the microlens and plate microcavity simultaneously reduces the mode volume (∼3.66 μm3) and suppresses diffraction and transverse walk-off loss, which induces discretization on energy-momentum dispersions and spatial electromagnetic-field distributions. The Q factor and Purcell factor of our lasing come out on top among most of the reported perovskite microcavities, paving a promising avenue toward further studying electrically driven on-chip microlasers.

Single-Crystal-Assisted In Situ Phase Reconstruction Enables Efficient and Stable 2D/3D Perovskite Solar Cells

Perovskite solar cells (PSCs) that incorporate both two-dimensional (2D) and three-dimensional (3D) phases possess the potential to combine the high stability of 2D PSCs with the superior efficiency of 3D PSCs. Here, we demonstrated in situ phase reconstruction of 2D/3D perovskites using a 2D perovskite single-crystal-assisted method. A gradient phase distribution of 2D RP perovskites was formed after spin-coating a solution of the 2D Ruddlesden-Popper (RP) perovskite single crystal, (DFP)2PbI4, onto the 3D perovskite surface, followed by thermal annealing. The resulting film exhibits much reduced trap density, increased carrier mobility, and superior water resistance. As a result, the optimized 2D/3D PSCs achieved a champion efficiency of 24.87% with a high open-circuit voltage (VOC) of 1.185 V. This performance surpasses the control 3D perovskite device, which achieved an efficiency of 22.43% and a VOC of 1.129 V. Importantly, the unencapsulated device demonstrates significantly enhanced operational stability, preserving over 97% of its original efficiency after continuous light irradiation for 1500 h. Moreover, the extrapolated T80 lifetimes surpass 5700 h. These findings pave the way for rational regulation of the gradient phase distribution at the interface between 2D and 3D perovskites by employing 2D RP perovskite crystals to achieve stable and efficient PSCs.

Bilayer 2D-3D Perovskite Heterostructures for Efficient and Stable Solar Cells

With a stacking-layered architecture, the bilayer two-dimensional-three-dimensional (2D-3D) perovskite heterostructure (PHS) not only eliminates surface defects but also protects the 3D perovskite matrix from external stimuli. However, these bilayer 2D-3D PHSs suffer from impaired interfacial charge carrier transport due to the relatively insulating 2D perovskite fragments with a random phase distribution. Over the past decade, substantial efforts have been devoted to pioneering molecular and structural designs of the 2D perovskite interlayers for improving their charge carrier mobility, which enables state-of-the-art perovskite solar cells with high power conversion efficiency and exceptional operational stability. Herein, this review offers a comprehensive and up-to-date overview on the recent progress of bilayer 2D-3D PHSs, encompassing advancements on spacer cation engineering, interfacial charge carrier modification, advanced deposition protocols, and characterization techniques. Then, the evolutionary trajectory of bilayer 2D-3D PHSs is outlined by summarizing its mainstream development trends, followed by a perspective discussion about its future research opportunities toward efficient and durable perovskite solar cells.

Crystal Growth, Structural and Electronic Characterizations of Zero-Dimensional Metal Halide (TEP)InBr4 Single Crystals for X-Ray Detection

Recently, metal halides have shown great potential for applications such as solar energy harvesting, light emission, and ionizing radiation detection. In this work, we report the preparation, structural, thermal, and electronic properties of a new zero-dimensional (0D) halide (TEP)InBr4 (where TEP is tetraethylphosphonium organic cation, C8H20P+). (TEP)InBr4 single crystals are obtained within a few days of continuous crystal growth time via a solution growth methodology. (TEP)InBr4 shows a relatively large optical bandgap energy of 4.32 eV and a low thermal conductivity between 0.33±0.05 and 0.45±0.07 W/m-K. Based on the density functional theory (DFT) calculations, the highest occupied molecular orbitals (HOMOs) of (TEP)InBr4 are dominated by the Br states, while the lowest unoccupied molecular orbitals (LUMOs) are constituted by both In and Br states. (TEP)InBr4 single crystals exhibit a semiconductor resistivity of 1.73×1013 Ω·cm and a mobility-lifetime (mu-tau) product of 2.07×10-5 cm2/V. Finally, a prototype (TEP)InBr4 single crystal-based X-ray detector with a detection sensitivity of 569.85 uCGy-1cm-2 (at electrical field E=100 V/mm) was fabricated, indicating the potential use of (TEP)InBr4 for radiation detection applications.