Efficient and Stable CsPbI₃ Solar Cells via Regulating Lattice Distortion with Surface Organic Terminal Groups

Abstract

All‐inorganic cesium lead iodide perovskites (CsPbI3) are promising wide‐bandgap materials for use in the perovskite/silicon tandem solar cells, but they easily undergo a phase transition from a cubic black phase to an orthorhombic yellow phase under ambient conditions. It is shown that this phase transition is triggered by moisture that causes distortion of the corner‐sharing octahedral framework ([PbI6]4−). Here, a novel strategy to suppress the octahedral tilting of [PbI6]4− units in cubic CsPbI3 by systematically controlling the steric hindrance of surface organic terminal groups is provided. This steric hindrance effectively prevents the lattice distortion and thus increases the energy barrier for phase transition. This mechanism is verified by X‐ray diffraction measurements and density functional theory calculations. Meanwhile, the formation of an organic capping layer can also passivate the surface electronic trap states of perovskite absorber. These modifications contribute to a stable power conversion efficiency (PCE) of 13.2% for the inverted planar perovskite solar cells (PSCs), which is the highest efficiency achieved by the inverted‐structure inorganic PSCs. More importantly, the optimized devices retained 85% of their initial PCE after aging under ambient conditions for 30 days.

Alkyl‐Chain‐Regulated Charge Transfer in Fluorescent Inorganic CsPbBr3 Perovskite Solar Cells

“…C12‐QDs tailored device achieves a higher V bi of 1.32 V, which is an indicator of reduced screening effect caused by charge carrier recombination. This is mainly attributed to the larger driving force (the energy levels of QDs are provided in Supplementary Figure S4) and reduced interface trap states . Furthermore, the larger slope of device tailored with C12‐QDs than that of other PSCs means a lower interfacial charge density, suggesting an improved charge extraction behavior.…”

Dopant‐Free Organic Hole‐Transporting Material for Efficient and Stable Inverted All‐Inorganic and Hybrid Perovskite Solar Cells

“…[ 28–31 ] Widely used inorganic HTMs in PVSCs include CuSCN, NiO x , etc., [ 32–36 ] which are typically considered more stable than organic HTMs, but their relatively low intrinsic conductivity and surface defects limit the PCE of the device. Organic HTMs are mostly based on polymeric materials, e.g., poly(triarylamine), poly(3‐hexylthiophene), poly(3,4‐ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS), [ 37–41 ] which could cause processability difficulties and batch‐to‐batch variations. [ 42 ] In contrast, dopant‐free organic small‐molecular HTMs could achieve highly efficient PVSCs and have much better processability, reproducibility, higher transmittance in the visible region, tunable energy levels, and improved long‐term stability.…”

Flexible and Self‐Powered Lateral Photodetector Based on Inorganic Perovskite CsPbI3–CsPbBr3 Heterojunction Nanowire Array

“…Inorganic perovskites possess strong light absorption, high carrier mobility, and good stability, and have been widely explored in many fields such as solar cells and photodetectors. [ 1–13 ] Specifically, self‐powered perovskite photodetector can work without external energy source, depending on a built‐in electric field which can separate the light‐induced carrier. [ 14–16 ] The most studied device type is the vertical heterojunction.…”