Sn-Based Perovskite Halides for Electronic Devices

Molecular Interlayer for High-Performance and Stable 2D Tin Halide Perovskite Transistor

Tin (Sn) halide perovskites present considerable potential for the advancement of high-performance p-channel field-effect transistors (FETs), attributable to their low hole effective mass and reduced carrier scattering. However, their intrinsic instability has impeded their ability to achieve the anticipated performance benchmarks. In this study, molecular interlayers are designed that not only passivate surface defects in Sn perovskites through their functional groups, leading to improved film formation and consequently enhanced performance and stability but also reduce the energy barrier at the source and drain interfaces through their strong dipole moments, thereby enhancing carrier transport. These synergistic effects result in FET devices exhibiting remarkable performance metrics, including effective mobility exceeding 11 cm2 V-1 s-1 and an on/off ratio greater than 1.3 × 107 while securing exceptional durability and reproducibility. Furthermore, the hydrophobic characteristics of the surface interlayer confer superior storage stability.

Plasma-Enhanced Grain Growth and Non-Radiative Recombination Mitigation in CsSnBr3 Perovskite Films for High-Performance, Lead-Free Photodetectors

Tin-based halide perovskites represent a highly promising and eco-friendly alternative to lead-based materials with significant potential for optoelectronic applications. However, their advancement is hampered by challenges such as poor film crystallinity and unintended self-doping. Herein, this work reports the fabrication of high-quality CsSnBr3 perovskite films by plasma-assisted chemical vapor deposition (PACVD), which improves the film quality. The precise control of the ammonia plasma not only promotes grain growth and reduces grain boundaries, but also eliminates defect states in the film, mitigates oxidation of Sn2+, suppresses sub-bandgap absorption, and reduces non-radiative recombination. Consequently, the photodetectors deliver exceptional performance, including a responsivity of 11.2 A W-1, a detectivity of 2.5 × 1011 Jones, and an ultrafast response time of 1/3.3 ms. Notably, certain key metrics, including detectivity (D*) and response time, significantly surpass those of all previously reported photoconductor-type Sn-based perovskite photodetectors. The results offer not only a novel strategy for enhancing the quality and optoelectronic performance of CsSnBr3 films but also a scalable platform for the development of high-performance, lead-free perovskite materials and devices. The new knowledge opens new possibilities for the design and fabrication of sustainable materials for advanced optoelectronic applications.

Solvent-Free Ball Milling Synthesis of Water-Stable Tin-Based Pseudohalide Perovskites for Photocatalytic CO2 Reduction

A pseudohalide (SCN-) tin-based perovskite material using a solvent-free ball milling method is developed. The synthesized perovskite exhibits long-term water stability and demonstrated significant photocatalytic activity in reducing CO2 to CO under light irradiation. The structural transition from nanoparticles to planar perovskites is achieved by varying the ratios of dimethylammonium (DMA) and formamidinium (FA) cations, which is confirmed by X-ray diffraction (XRD) and scanning electron microscopy (SEM) analyses. The surface elemental distribution, absorption spectra, band gap and energy levels estimations using energy-dispersive X-ray spectroscopy (EDS), Kubelka-Munk function, and ultraviolet photoelectron spectroscopy (UPS) are thoroughly investigated. These findings indicated that the incorporation of DMA cations increased the band gap and shifted the absorption spectra toward the blue region. The optimal photocatalytic performance is observed for the perovskite composition with a 50% DMA cation ratio (DMA0.5FA0.5SnI(SCN)2), achieving a CO production yield of 285 µmol g-1 with 12 hours irradiation in humid environment. The efficiency is critically dependent on the ball milling speed and duration, with 400 rpm and 1 hour being the optimal conditions. This research highlights the potential of environmentally friendly synthesis methods in developing stable and efficient lead-free perovskites as photocatalytic materials, contributing to the goal of net-zero carbon emissions.

Improving the Antioxidant Properties of Tin-Based Perovskite for the Enhanced Performance of Near-Infrared Light-Emitting Diodes Through the Synergy of Sn and SnF2

Tin-based perovskite has emerged as an excellent luminescent material due to its non-toxicity and narrow bandgap compared to lead-based perovskite. However, its tin ions are easily oxidized by oxygen, which leads to increased vacancy defects and poor crystallinity, presenting a significant challenge in obtaining high-quality perovskite films. In this context, we introduced an approach by synergistically adding SnF2 and tin powder into the precursor solution to enhance the antioxidation of Sn ions. This method effectively improved the crystallinity of the perovskite films, reduced the density of defect states, and enhanced the photoluminescence performance of the films. Based on these findings, we successfully fabricated tin-based near-infrared perovskite light-emitting diodes (PeLEDs). With a 20% improvement in the Sn2+ content in the film, we achieved a threefold increase in the external quantum efficiency of the devices, reaching 3.6%.

Single Crystal Sn-Based Halide Perovskites

Sn-based halide perovskites are expected to be the best replacement for toxic lead-based counterparts, owing to their similar ionic radii and the optimal band gap for use in solar cells, as well as their versatile use in light-emitting diodes and photodetection applications. Concerns, however, exist about their stability under ambient conditions, an issue that is exacerbated in polycrystalline films because grain boundaries present large concentrations of defects and act as entrance points for oxygen and water, causing Sn oxidation. A current thriving research area in perovskite materials is the fabrication of perovskite single crystals, promising improved optoelectronic properties due to excellent uniformity, reduced defects, and the absence of grain boundaries. This review summarizes the most recent advances in the fabrication of single crystal Sn-based halide perovskites, with emphasis on synthesis methods, compositional engineering, and formation mechanisms, followed by a discussion of various challenges and appropriate strategies for improving their performance in optoelectronic applications.

Recent Progress of Quantum Dots Light-Emitting Diodes: Materials, Device Structures, and Display Applications

Colloidal quantum dots (QDs), as a class of 0D semiconductor materials, have generated widespread interest due to their adjustable band gap, exceptional color purity, near-unity quantum yield, and solution-processability. With decades of dedicated research, the potential applications of quantum dots have garnered significant recognition in both the academic and industrial communities. Furthermore, the related quantum dot light-emitting diodes (QLEDs) stand out as one of the most promising contenders for the next-generation display technologies. Although QD-based color conversion films are applied to improve the color gamut of existing display technologies, the broader application of QLED devices remains in its nascent stages, facing many challenges on the path to commercialization. This review encapsulates the historical discovery and subsequent research advancements in QD materials and their synthesis methods. Additionally, the working mechanisms and architectural design of QLED prototype devices are discussed. Furthermore, the review surveys the latest advancements of QLED devices within the display industry. The narrative concludes with an examination of the challenges and perspectives of QLED technology in the foreseeable future.

Controlling Tin Halide Perovskite Oxidation Dynamics in Solution for Perovskite Optoelectronic Devices

As a leading contender to replace lead halide perovskites, tin-based perovskites have demonstrated ever increasing performance in solar cells and light-emitting diodes (LEDs). They tend to be processed with dimethyl sulfoxide (DMSO) solvent, which has been identified as a major contributor to the Sn(II) oxidation during film fabrication, posing a challenge to the further improvement of Sn-based perovskites. Herein, we use NMR spectroscopy to investigate the kinetics of the oxidation of SnI2, revealing that autoamplification takes place, accelerating the oxidation as the reaction progresses. We propose a mechanism consistent with these observations involving water participation and HI generation. Building upon these insights, we have developed low-temperature Sn-based perovskite LEDs (PeLEDs) processed at 60 °C, achieving enhanced external quantum efficiencies (EQEs). Our research underscores the substantial potential of low-temperature DMSO solvent processes and DMSO-free solvent systems for fabricating oxidation-free Sn-based perovskites, shaping the future direction in processing Sn-containing perovskite materials and optoelectronic devices.

A-Site Cations Impact on Nonradiative Recombination, Mobility, and Defect Dynamics in Sn-Based Perovskites

Sn-based perovskites with different cations in the A-site exhibit distinct electronic structures and dynamic properties. By utilizing time-dependent density functional theory and nonadiabatic molecular dynamics, we demonstrate that larger FA cations decrease wave function overlap between initial and final states and slow down nuclear motion. In the case of FASnI3, this alteration decreases the nonadiabatic coupling and increases the nonradiative electron-hole recombination time by 130% and 76%, respectively, compared to CsSnI3 and MASnI3 (CH3NH3SnI3). Furthermore, A-site modification significantly improves electron mobility and changes the properties of defects in FASnI3 (HC(NH2)2SnI3), which achieves higher electron mobility through a polar optical phonon-dominated scattering mechanism and exhibits higher defect formation energy and migration barriers of A-site cations due to increased steric hindrance, relative to CsSnI3 and MASnI3. These results emphasize the critical function of A-site cation substitution in controlling nonradiative recombination dynamics, electron mobility, and defect characteristics in Sn-based perovskites and provide theoretical insights for the advancement of novel lead-free perovskite materials.

Tuning the dimensionality in chiral and racemic organic/tin hybrids with halides

Chiral 1D tin iodides EBASnI3 were synthesized while incorporating enantiomerically pure and racemic ethylbenzylammonium (EBA) cations between the 1D shared inorganic corners. The dimensionality was reduced to 0D when replacing iodine with bromine. In all the cases, the presence of hydrogen bonds was observed between the organic part and the inorganic part, while transfer of chirality was evidenced for the EBASnI3 enantiomerically pure compounds.

Exploring Non-Toxic Lower Dimensional Perovskites for Next-Generation X-Ray Detectors

Owing to their extraordinary photophysical properties, organometal halide perovskites are emerging as a new material class for X-ray detection. However, the existence of toxic lead makes their commercialization questionable and should readily be replaced. Accordingly, several lead alternatives have been introduced into the framework of conventional perovskites, resulting in various new perovskite dimensionalities. Among these, Pb-free lower dimensional perovskites (LPVKs) not only show promising X-ray detecting properties due to their higher ionic migration energy, wider and tunable energy bandgap, smaller dark currents, and structural versatility but also exhibit extended environmental stability. Herein, first, the structural organization of the PVKs (including LPVKs) is summarized. In the context of X-ray detectors (XDs), the outstanding properties of the LPVKs and active layer synthesis routes are elaborated afterward. Subsequently, their applications in direct XDs are extensively discussed and the device performance, in terms of the synthesis method, device architecture, active layer size, figure of merits, and device stability are tabulated. Finally, the review is concluded with an in-depth outlook, thoroughly exploring the present challenges to LPVKs XDs, proposing innovative solutions, and future directions. This review provides valuable insights into optimizing non-toxic Pb-free perovskite XDs, paving the way for future advancements in the field.

Enhancing the Performance of 2D Tin-Based Pure Red Perovskite Light-Emitting Diodes through the Synergistic Effect of Natural Antioxidants and Cyclic Molecular Additives

Tin (Sn)-based perovskites are being investigated in many optoelectronic applications given their similar valence electron configuration to that of lead-based perovskites and the potential environmental hazards of lead-based perovskites. However, the formation of high-quality Sn-based perovskite films faces several challenges, mainly due to the easy oxidation of Sn2+ to Sn4+ and the fast crystallization rate. Here, to develop an environmentally friendly process for Sn-based perovskite fabrication, a series of natural antioxidants are studied as additives and ascorbic acid (VitC) is found to have a superior ability to inhibit the oxidation problem. A common cyclic molecule, 18-Crown-6, is further added as a second additive, which synergizes with VitC to significantly reduce the nonradiative recombination pathways in the PEA2SnI4 film. This synergistic effect greatly improves the performance of 2D red Sn-based PeLED, with a maximum external quantum efficiency of 1.87% (≈9 times that of the pristine device), a purer color, and better bias stability. This work demonstrates the potential of the dual-additive approach in enhancing the performance of 2D Sn-based PeLEDs, while the use of these environmentally friendly additives contributes to their future sustainability.

Alkylammonium Halides for Phase Regulation and Luminescence Modulation of Cesium Copper Iodide Nanocrystals for Light-Emitting Diodes

All-inorganic cesium copper halide nanocrystals have attracted extensive attention due to their cost-effectiveness, low toxicity, and rich luminescence properties. However, controlling the synthesis of these nanocrystals to achieve a precise composition and high luminous efficiency remains a challenge that limits their future application. Herein, we report the effect of oleylammonium iodide on the synthesis of copper halide nanocrystals to control the composition and phase and modulate their photoluminescence (PL) quantum yields (QYs). For CsCu2I3, the PL peak is centered at 560 nm with a PLQY of 47.3%, while the PL peak of Cs3Cu2I5 is located at 440 nm with an unprecedently high PLQY of 95.3%. Furthermore, the intermediate-state CsCu2I3/Cs3Cu2I5 heterostructure shows white light emission with a PLQY of 66.4%, chromaticity coordinates of (0.3176, 0.3306), a high color rendering index (CRI) of 90, and a correlated color temperature (CCT) of 6234 K, indicating that it is promising for single-component white-light-emitting applications. The nanocrystals reported in this study have excellent luminescence properties, low toxicity, and superior stability, so they are more suitable for future light-emitting applications.