Multilayer Cascade Charge Transport Layer for High‐Performance Inverted Mesoscopic All‐Inorganic and Hybrid Wide‐Bandgap Perovskite Solar Cells

It is imperative to improve the quality of light absorber and reduce the charge‐carrier recombination for efficient perovskite solar cells (PSCs). Herein, a synergistic regulation strategy that combines the tailoring of crystallinity and construction of multilayer cascade charge transport layers (CTLs) for inverted CsPbI 2 Br solar cells is presented. The film quality of CsPbI 2 Br is well tuned via F − doping. In addition, gradient energy alignment between perovskite and CTLs, i.e., NiO x /Zn:CuGaO 2 /perovskite and perovskite/TiO 2 /PC 61 BM/ZnO, favors the charge transfer and depresses carrier recombination. Noticeably, the TiO 2 interlayer with deep valence band maximum effectively blocks the hole back‐transfer from perovskite to PC 61 BM. These unique characteristics of the novel structured CsPbI 2 Br device give a champion power conversion efficiency (PCE) of 15.10% along with good thermal and operational stability. Moreover, the graded CTLs can be expanded to methylammonium‐free hybrid perovskite device ( E g = ≈1.76 eV) by delivering a PCE of 18.12%, showing great promise in tandem solar cells for use as top cell.