The photovoltaics of organic–inorganic lead halide perovskite materials have shown rapid improvements in solar cell performance, surpassing the top efficiency of semiconductor compounds such as CdTe and CIGS (copper indium gallium selenide) used in solar cells in just about a decade. Perovskite preparation via simple and inexpensive solution processes demonstrates the immense potential of this thin-film solar cell technology to become a low-cost alternative to the presently commercially available photovoltaic technologies. Significant developments in almost all aspects of perovskite solar cells and discoveries of some fascinating properties of such hybrid perovskites have been made recently. This Review describes the fundamentals, recent research progress, present status, and our views on future prospects of perovskite-based photovoltaics, with discussions focused on strategies to improve both intrinsic and extrinsic (environmental) stabilities of high-efficiency devices. Strategies and challenges regardi...

Halide Perovskite Photovoltaics: Background, Status, and Future Prospects

Lead halide perovskites (LHPs) in the form of nanometre-sized colloidal crystals, or nanocrystals (NCs), have attracted the attention of diverse materials scientists due to their unique optical versatility, high photoluminescence quantum yields and facile synthesis. LHP NCs have a 'soft' and predominantly ionic lattice, and their optical and electronic properties are highly tolerant to structural defects and surface states. Therefore, they cannot be approached with the same experimental mindset and theoretical framework as conventional semiconductor NCs. In this Review, we discuss LHP NCs historical and current research pursuits, challenges in applications, and the related present and future mitigation strategies explored.

/pdf/genesis-challenges-and-opportunities-for-colloidal-lead-3uh77e26ys.pdf

Genesis, challenges and opportunities for colloidal lead halide perovskite nanocrystals

This review article examines the current state of understanding in how metal halide perovskite solar cells can degrade when exposed to moisture, oxygen, heat, light, mechanical stress, and reverse bias. It also highlights strategies for improving stability, such as tuning the composition of the perovskite, introducing hydrophobic coatings, replacing metal electrodes with carbon or transparent conducting oxides, and packaging. The article concludes with recommendations on how accelerated testing should be performed to rapidly develop solar cells that are both extraordinarily efficient and stable.

Understanding Degradation Mechanisms and Improving Stability of Perovskite Photovoltaics.

Metal halide perovskites represent a flourishing area of research, driven by both their potential application in photo-voltaics and optoelectronics, and for the fundamental science underpinning their unique optoelectronic properties. The advent of colloidal methods for the synthesis of halide perovskite nanocrystals has brought to the attention inter-esting aspects of this new type of materials, above all their defect-tolerance. This review aims to provide an updated survey of this fast-moving field, with a main focus on their colloidal synthesis. We examine the chemistry and the ca-pability of different colloidal synthetic routes to control the shape, size and optical properties of the resulting nano-crystals. We also provide an up to date overview of their post-synthesis transformations, and summarize the various so-lution processes aimed at fabricating halide perovskite-based nanocomposites. We then review the fundamental optical properties of halide perovskite nanocrystals, by focusing on their linear optical properties, on the effects of quantum confinement and, then, on the current knowledge of their exciton binding energies. We also discuss the emergence of non-linear phenomena such as multiphoton absorption, biexcitons and carrier multiplication. At last, we provide an outlook in the field, with the most cogent open questions and possible future directions.

Metal Halide Perovskite Nanocrystals: Synthesis, Post-Synthesis Modifications and Their Optical Properties

Metal halide perovskites represent a flourishing area of research, which is driven by both their potential application in photovoltaics and optoelectronics and by the fundamental science behind their unique optoelectronic properties. The emergence of new colloidal methods for the synthesis of halide perovskite nanocrystals, as well as the interesting characteristics of this new type of material, has attracted the attention of many researchers. This review aims to provide an up-to-date survey of this fast-moving field and will mainly focus on the different colloidal synthesis approaches that have been developed. We will examine the chemistry and the capability of different colloidal synthetic routes with regard to controlling the shape, size, and optical properties of the resulting nanocrystals. We will also provide an up-to-date overview of their postsynthesis transformations, and summarize the various solution processes that are aimed at fabricating halide perovskite-based nanocomposites. Furthermore, we...

Metal Halide Perovskite Nanocrystals: Synthesis, Post-Synthesis Modifications, and Their Optical Properties.

All-inorganic CsPbI3 perovskite is emerging to be an alternative light-harvesting material in solar cells owing to the enhanced stability and comparable photovoltaic performance compared to organic–inorganic hybrid perovskites. However, the desirable black phase α-CsPbI3 is not stable at room temperature and degrades rapidly to a nonperovskite yellow phase δ-CsPbI3. Herein, we introduce a compositional engineering approach via incorporating Bi3+ in CsPbI3 to stabilize the α-phase at room temperature. Fully inorganic solar cells based on the Bi-incorporated α-CsPb1–xBixI3 compounds demonstrate a high PCE of 13.21% at an optimal condition (incorporation of 4 mol % Bi3+) and maintain 68% of the initial PCE for 168 h under ambient conditions without encapsulation. This is the first attempt of partial substitution of the “B”-site of the perovskite to stabilize the α-CsPbI3, which paves the way for further developments of such perovskites and other optoelectronic devices.

Bismuth Incorporation Stabilized α-CsPbI3 for Fully Inorganic Perovskite Solar Cells

Lead-free, air-stable ultrathin Cs3Bi2I9 perovskite nanosheets for solar cells

Highly Efficient and Stable Solar Cells with 2D MA3Bi2I9/3D MAPbI3 Heterostructured Perovskites

The growth of single crystals allows a more accurate and reliable study of the intrinsic electrical and optical properties of halide perovskite materials. However, all-inorganic halide perovskite single crystals are difficult to prepare due to the poor solubility of the reactant precursors. In this paper, we report a series of air-stable Cs-based halide perovskite single crystals, CsPbBr3 and CsPb1−xBixBr3 (x ≪ 1), prepared via a modified antisolvent vapour-assisted crystallization method. The Cs-based halide perovskites exhibited low trap density and high carrier mobility that are comparable to those of organic–inorganic hybrid halide perovskite materials. Most importantly, the Bi-doped CsPb1−xBixBr3 perovskites also indicated excellent light absorption (covering the entire visible wavelength) and photostriction (effective photostriction of about 8 × 10−4) performances, which greatly expands the optoelectronic and optomechanical applications of these inorganic halide perovskite materials.

Air-stable CsPb1−xBixBr3 (0 ≤ x ≪ 1) perovskite crystals: optoelectronic and photostriction properties

Methylammonium lead halide (MAPbX3) perovskites have attracted tremendous attention due to their remarkable performances in solar cells, light-emitting diodes, photodetectors, lasers, and electronic memories. However, the issue of toxicity still greatly restricts their further large-scale applications. Here, this study presents a series of nontoxic and stable methylammonium (or cesium) bismuth halides A3Bi2I9 (A = Cs+ and MA+) nanosheets for using in flexible memories. The ultrathin A3Bi2I9 nanosheets can be easily prepared by a dissolution–recrystallization process. This is the first attempt that reports the ultrathin bismuth halides and explores their potential applications in flexible electronic devices. The flexible memristors based on such ultrathin Cs3Bi2I9 nanosheets exhibit typical bipolar resistive switching behavior and remarkable characteristics such as high Ron/Roff ratio (≈103), very low working voltage (≈0.3 V), and long data retention (>104 s), as well as excellent endurability, reproducibility, environmental stability, and flexibility. With such appealing characteristics, the cesium bismuth halide memristors have great potential for practical applications. The results of this work demonstrate that cesium bismuth halide ultrathin nanosheets will be promising candidates for more emerging applications in electronics and optoelectronics such as memories, photodetectors, photovoltaics, and light-emitting diodes.

Fan Bai

Papers

Bismuth Incorporation Stabilized α-CsPbI3 for Fully Inorganic Perovskite Solar Cells

Lead-free, air-stable ultrathin Cs3Bi2I9 perovskite nanosheets for solar cells

Highly Efficient and Stable Solar Cells with 2D MA3Bi2I9/3D MAPbI3 Heterostructured Perovskites

Air-stable CsPb1−xBixBr3 (0 ≤ x ≪ 1) perovskite crystals: optoelectronic and photostriction properties

Ultrathin Cs3Bi2I9 Nanosheets as an Electronic Memory Material for Flexible Memristors