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Hole transport materials (HTMs) are essential for improving the stability and efficiency of perovskite solar cells (PSCs). In this study, we have designed and synthesized a novel organic small molecule HTM, cor‐(DPA)5, characterized by a bowl‐shaped core with symmetric five diphenylamine groups. Compared to already‐known HTMs, the bowl‐shaped and relatively compact structure of cor‐(DPA)5 facilitates intermolecular π–π interactions, promotes film formations, and enhances charge transport. Consequently, the cor‐[DPA(2)]5 HTM exhibits high charge mobility, exceptional hydrophobicity, and a significantly elevated glass transition temperature. Superior to previously reported HTMs such as spiro‐OMeTAD and cor‐OMePTPA, our newly synthesized cor‐(DPA)5 HTM is free from any ionic dopants. As a result, the dopant‐free cor‐[DPA(2)]5‐based PSC demonstrates an impressive efficiency of 24.01 %, and exhibits outstanding operational stability. It retains 96 % after continuous exposure to 1 sun irradiation for 800 hours under MPP (maximum power point) tracking in ambient air. These findings present a structurally compact novel HTM and exemplify a new approach to the molecular design of HTM for the development of stable and effective PSCs. [ABSTRACT FROM AUTHOR]

[Display omitted] • Corannulene-cored molecules acted as novel HTMs for inverted PSCs. • Excellent molecular/film properties offered a remarkable hole-transporting process. • Cor-SMePTPA-based PSC achieved a highest PCE of 21.7% with an excellent stability. • The molecular/film effects on photovoltaic parameters of the device were elucidated. Hole transporting materials (HTMs), owing to their unique bottom position in inverted perovskite solar cells (PSCs), exert a considerable influence on the hole-transporting process and the morphology/performance of the perovskite layers. Considering the well-known interfacial problems associated with commonly-used NiO x and poly(triarylamine) HTMs in traditional inverted PSCs, there is an urgent need for exploring efficient HTMs exhibiting good film formability/processability and interfacial contact to meet the specific requirements of high-performance and stable inverted PSCs. Herein, we fabricated inverted PSCs involving two star-like, dopant-free, corannulene-cored HTMs with O-terminals (sym -penta(N, N -bis(4-methoxyphenyl)aniline)corannulene, namely Cor-OMePTPA) and S-terminals (sym -penta(N, N -bis(4-(methylthio)phenyl)aniline)corannulene, namely Cor-SMePTPA) for the first time. The Cor-SMePTPA HTM exhibited a stronger hole-transporting ability and a better interfacial chemical linkage when compared to the Cor-OMePTPA HTM. The device containing Cor-SMePTPA HTM delivered a power conversion efficiency of 21.70%, which was the highest among inverted PSCs based on methylthio (SMe)-terminated HTMs. Furthermore, comprehensive experimental and theoretical characterizations clearly showed that the core and outer terminals (O or S) affected the optoelectric and chemical properties of the HTMs as well as the photovoltaic performance and stability of the corresponding PSCs, highlighting the superiority of the design involving a corannulene core and SMe groups in HTMs for inverted PSCs. We believe that such dopant-free corannulene-cored HTMs can have considerable potential for realizing highly efficient and stable PSCs in the future. [ABSTRACT FROM AUTHOR]