Asymmetrically Substituted 10<i>H</i>,10′<i>H</i>‐9,9′‐Spirobi[acridine] Derivatives as Hole‐Transporting Materials for Perovskite Solar Cells

Abstract Hole‐transporting materials (HTMs) based on the 10 H , 10′ H ‐9,9′‐spirobi [acridine] core ( BSA50 and BSA51 ) were synthesized, and their electronic properties were explored. Experimental and theoretical studies show that the presence of rigid 3,6‐dimethoxy‐9H‐carbazole moieties in BSA 50 brings about improved hole mobility and higher work function compared to bis(4‐methoxyphenyl)amine units in BSA51 , which increase interfacial hole transportation from perovskite to HTM. As a result, perovskite solar cells (PSCs) based on BSA50 boost power conversion efficiency (PCE) to 22.65 %, and a PSC module using BSA50 HTM exhibits a PCE of 21.35 % (6.5×7 cm) with a V oc of 8.761 V and FF of 79.1 %. The unencapsulated PSCs exhibit superior stability to devices employing spiro‐OMeTAD, retaining nearly 90 % of their initial efficiency after 1000 h operation output. This work demonstrates the high potential of molecularly engineered spirobi[acridine] derivatives as HTMs as replacements for spiro‐OMeTAD.