Constructing Chromium Multioxide Hole-Selective Heterojunction for High-Performance Perovskite Solar Cells

Perovskite solar cells (PSCs) suffer from significant nonradiative recombination at perovskite/charge transport layer heterojunction, seriously limiting their power conversion efficiencies. Herein, solution-processed chromium multioxide (CrO_x) is judiciously selected to construct a MAPbI₃/CrO_x/Spiro-OMeTAD hole-selective heterojunction. It is demonstrated that the inserted CrO_x not only effectively reduces defect sites via redox shuttle at perovskite contact, but also decreases valence band maximum (VBM)-HOMO offset between perovskite and Spiro-OMeTAD. This will diminish thermionic losses for collecting holes and thus promote charge transport across the heterojunction, suppressing both defect-assisted recombination and interface carrier recombination. As a result, a remarkable improvement of 21.21% efficiency with excellent device stability is achieved compared to 18.46% of the control device, which is among the highest efficiencies for polycrystalline MAPbI₃ based n–i–p planar PSCs reported to date. These findings of this work provide new insights into novel charge-selective heterojunctions for further enhancing efficiency and stability of PSCs.