Hole Transport Materials Based on 6,12-Dihydroindeno[1,2-b]fluorine with Different Periphery Groups: A New Strategy for Dopant-Free Perovskite Solar Cells

Although several hole-transporting materials (HTMs) have been designed to obtain perovskite solar cells (PSCs) devices with high performance, the dopant-free HTMs for efficient and stable PSCs remain rare. Herein, a rigid planar 6,12-dihydroindeno[1,2-b]fluorine (IDF) core with different numbers of bulky periphery groups to construct dopant-free HTMs of IDF-SFXPh, IDF-DiDPA, and IDF-TeDPA is modified. Thanks to the contributions of the planar IDF core and the twisted SFX periphery groups, the dopant-free IDF-SFXPh-based PSCs device achieves a device performance of 17.6%, comparable to the doped 2,2 ',7,7 '-tetrakis(N,N-di-p-methoxyphenylamine)-9,9 '-spirobifluorene (spiro-OMeTAD)-based device (17.6%), with much enhanced device stability under glovebox and ambient conditions.