Polymer hole-transport material improving thermal stability of inorganic perovskite solar cells

Cesium-based inorganic perovskite solar cells (PSCs) are paid more attention because of their potential thermal stability. However, prevalent salt-doped 2,2',7,7'-tetrakis(N,N-dipmethoxyphenylamine)9,9'-spirobifluorene (Spiro-OMeTAD) as hole-transport materials (HTMs) for a high-efficiency inorganic device has an unfortunate defective thermal stability. In this study, we apply poly (3-hexylthiophene-2,5-diyl) (P3HT) as the HTM and design all-inorganic PSCs with an indium tin oxide (ITO)/SnO₂/LiF/CsPbI_3-xBr_x/P3HT/Au structure. As a result, the CsPbI_3-xBr_x PSCs achieve an excellent performance of 15.84%. The P3HT HTM-based device exhibits good photo-stability, maintaining ∼80% of their initial power conversion efficiency over 280 h under one Sun irradiation. In addition, they also show better thermal stability compared with the traditional HTM Spiro-OMeTAD.