Dual-Interface Modification of CsPbIBr₂ Solar Cells with Improved Efficiency and Stability

The organic-inorganic hybrid perovskite solar cell has been a rising star in photovoltaics (PV) in the last decade due to its high efficiency and the fastest efficiency-rise among all known materials in the PV history. The newly developed all-inorganic perovskite, for its high stability against thermal and light irradiation stresses, is recognized as a promising material for both PV and general optoelectronic applications. Interface and its modification have been proven to play an important role in the solar cell performance. However, all previous research on the all-inorganic CsPbIBr₂ based solar cells limits their scope to only one surface/interface while ignoring the other. Herein, synergistic effect is discovered when proper amount of CsBr is introduced on both sides of the perovskite active layer. It is found that the TiO₂/perovskite interface modification reduces pinhole and trap-state densities while modification on perovskite/Spiro-OMeTAD promotes smoother surface and better crystallinity. The synergistic effect of both modifications leads to increased efficiency to 10.33% with V_OC of 1.24 V, both are among the highest for these types of solar cells. In addition, the optimized device retains 60% of its initial efficiency after 60 h of aging in ambient atmosphere.