Phase-heterojunction all-inorganic perovskite solar cells surpassing 21.5% efficiency

The fabrication of perovskite heterojunctions is challenging. Mali et al. develop a heterojunction with two different crystalline phases of CsPbI3, achieving 21.5% and 18.4% efficiencies on small-area solar cells and 18 cm(2) solar modules, respectively. Making organic-inorganic metal halide-based multijunction perovskite solar cells either by solution processes or physical techniques is not straightforward. Here we propose and developed dimethylammonium iodide-assisted & beta;-CsPbI3 and guanidinium iodide-assisted & gamma;-CsPbI3 all-inorganic phase-heterojunction solar cells (PHSs) by integrating hot-air and triple-source thermal evaporation deposition techniques, respectively. Incorporating a (Zn(C6F5)(2)) molecular additive and dopant-free hole transport layer produces a 21.59% power conversion efficiency (PCE). The laboratory-to-module scale shows 18.43% PCE with an 18.08 cm(2) active area. We demonstrate that this additive-assisted & beta;-& gamma;-based PHS structure exhibited >200 hours of stable performance under maximum power tracking under one sun illumination. This work paves the way towards dual deposition techniques for PHS with important consequences not only for all inorganic but also for other halide perovskite compositions.