Curing the fundamental issue of impurity phases in two-step solution-processed CsPbBr3 perovskite films

Research Progress of Green Solvent in CsPbBr3 Perovskite Solar Cells

In optoelectronic applications, all-Brominated inorganic perovskite CsPbBr₃ solar cells have received a great deal of attention because of their remarkable stability and simplicity of production. Most of the solvents used in CsPbBr₃ perovskite solar cells are toxic, which primarily hinders the commercialization of the products. In this review, we introduce the crystal structure and fundamental properties of CsPbBr₃ materials and the device structure of perovskite cells, summarize the research progress of green solvents for CsPbBr₃ PSCs in recent years from mono-green solvent systems to all-green solvent systems, and discuss the approaches to improving the PCE of CsPbBr₃ PSCs, intending to facilitate the sustainable development of CsPbBr₃ perovskite solar cells. Finally, we survey the future of green solvents in the area of CsPbBr₃ perovskite solar cells.

Simple and sustainable synthesis of perovskite-based optoelectronic material: CsPbBr3 nanocrystals via laser ablation in alcohol

All-inorganic lead halide perovskite nanocrystals (NCs) have shown great potential as emerging semiconducting materials due to their excellent optoelectronic properties. However, syntheses in solution commonly use high temperatures and toxic solvents, which are obstacles for safety and sustainability of the process. In this work, laser ablation in alcohol is proposed as a simple and sustainable, ligand-free, top-down approach to synthesize CsPbBr₃ nanocrystals in ambient conditions. The effects of different low boiling point commercial alcohols used as solvents on the optical properties of CsPbBr₃ NCs colloidal solutions are investigated. Although in traditional bottom-up synthesis alcohols are usually found to be not appropriate for the synthesis of perovskite NCs, here it is demonstrated that CsPbBr₃ orthorhombic nanocrystals with narrow full width half maximum (FWHM < 18 nm), long photoluminescence lifetimes (up to 17.9 ns) and good photoluminescence quantum yield (PLQY up to 15.5%) can be obtained by selecting the dielectric constant and polarity of the alcohol employed for the synthesis.

Generic water-based spray-assisted growth for scalable high-efficiency carbon-electrode all-inorganic perovskite solar cells

A water-based spray-assisted growth strategy is proposed to prepare large-area all-inorganic perovskite films for perovskite solar cells (PSCs), which involves in spraying of cesium halide water solution onto spin-coating-deposited lead halide films, followed by thermal annealing. With CsPbBr3 as an example, we show that as-proposed growth strategy can enable the films with uniform surface, full coverage, pure phase, large grains, and high crystallinity, which primarily benefits from the controllable CsBr loading quantity, and the use of water as CsBr solvent makes the reaction between CsBr and PbBr2 immune to PbBr2 film microstructure. As a result, the small-area (0.09 cm2) and large-area (1.00 cm2) carbon-electrode CsPbBr3 PSCs yield the record-high efficiencies of 10.22% and 8.21%, respectively, coupled with excellent operational stability. We also illustrate that the water-based spray-assisted deposition strategy is suitable to prepare CsPbCl3, CsPbIBr2, and CsPbI2Br films with outstanding efficiencies of 1.27%, 10.44%, and 13.30%, respectively, for carbon-electrode PSCs.

Oxidization-Free Spiro-OMeTAD Hole-Transporting Layer for Efficient CsPbI2Br Perovskite Solar Cells

The inorganic CsPbI₂Br perovskite faces serious challenges of low phase stability and high moisture sensitivity. The moisture controllable process of a hole-transporting layer (HTL) is crucial for the development of stable and efficient inorganic perovskite solar cells (IPSCs). In this work, we proposed an oxidization-free spiro-OMeTAD hole-transport layer (HTL) with a preoxidized spiro-OMeTAD solution to prevent moisture and completely avoid the phase transition of CsPbI₂Br from the α-phase to β-phase. The oxidization-free HTL exhibited improved surface hydrophobic properties, smoother morphology, and optimized energy-level alignment compared with a traditional HTL. As a result, the CsPbI₂Br-based IPSCs achieved an efficiency of up to 14.2 and 86.6% of the initial power conversion efficiency (PCE) with 2000 h storage. Meanwhile, this oxidization-free HTL was applied in CH₃NH₃PbI₃-based PSCs and obtained 13.8% PCE enhancement, which proved the universality of the solution preoxidization tactic. We believe that the oxidization-free HTL could be an efficient strategy to replace traditional HTLs and can be widely used in perovskite solar cells, especially in moisture-sensitive PSCs.