Thermal unequilibrium of strained black CsPbI ₃ thin films

Abstract

The high-temperature, all-inorganic CsPbI3 perovskite black phase is metastable relative to its yellow, nonperovskite phase at room temperature. Because only the black phase is optically active, this represents an impediment for the use of CsPbI3 in optoelectronic devices. We report the use of substrate clamping and biaxial strain to render black-phase CsPbI3 thin films stable at room temperature. We used synchrotron-based, grazing incidence, wide-angle x-ray scattering to track the introduction of crystal distortions and strain-driven texture formation within black CsPbI3 thin films when they were cooled after annealing at 330°C. The thermal stability of black CsPbI3 thin films is vastly improved by the strained interface, a response verified by ab initio thermodynamic modeling.

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

“…[ 34 ] However, there are few reports about the heterojunction based on the black phase CsPbI 3 , because this phase is unstable at room temperature and very sensitive to the moisture, which easily transfers into a yellow phase (δ‐phase) with a large bandgap. [ 35–39 ] In addition, the narrow depletion region of lateral heterojunction requires a pair of electrodes precisely located at the two sides of perovskite film, for which electron beam lithography (EBL) is always employed. The lithography process will accelerate the transformation into the yellow phase CsPbI 3 because of the utilization of the polar solvent.…”

Macroscopic and Microscopic Structures of Cesium Lead Iodide Perovskite from Atomistic Simulations

“…[ 7,8 ] Among such all‐inorganic hybrid perovskites, Cesium lead iodide (CsPbI 3 ), when crystallizing in the perovskite structure, is one of the most promising because its bandgap is nicely suitable for photovoltaics and because of its high solar cell conversion efficiencies. [ 7,9 ] Note, however, that the most stable CsPbI 3 structure is the so‐called yellow δ‐phase that is nonperovskite, while the optically‐active phases adopt the (metastable) perovskite structure and are the so‐called α‐(cubic, Pmm), β‐(tetragonal, P4/mbm), and γ‐phases (orthorhombic, Pnma) [ 1,10–16 ] [such latter phases are schematized in Figure a–c in the ideal case (for Pmm) or perfectly ordered situations (for P4/mbm and Pnma)]. In particular, solar cells using the orthorhombic γ‐phase display an efficiency of 11.3%, [ 12 ] while those made of the cubic α‐phase and the tetragonal β‐phase can have an efficiency of 17% [ 7 ] and 18%, [ 9 ] respectively.…”

A Review on Additives for Halide Perovskite Solar Cells

“…Besides large‐size amine cations, quantum dots have also been applied to stabilize CsPbI 3 significantly via lattice anchoring . More interestingly, strain was also applied to stabilize CsPbI 3 , indicating considering and utilizing localized energy distribution is quite important for halide perovskites …”