Abstract
Although doped hole-transport materials(HTMs)offer an efficiency benefit for perovskite solar cells(PSCs),they inevi-tably diminish the stability.Here,we describe the use of various chlorinated small molecules,specifically fluorenone-triphenylamine(FO-TPA)-x-C1[x=para,meta,and ortho(p,m,and o)],with different chlorine-substituent positions,as dopant-free HTMs for PSCs.These chlorinated molecules feature a symmetrical donor-acceptor-donor structure and ideal intramolecular charge transfer properties,allowing for self-doping and the establishment of built-in potentials for improving charge extraction.Highly efficient hole-transfer interfaces are constructed between perovskites and these HTMs by strategi-cally modifying the chlorine substitution.Thus,the chlorinated HTM-derived inverted PSCs exhibited superior efficiencies and air stabilities.Importantly,the dopant-free HTM FO-TPA-o-Cl not only attains a power conversion efficiency of 20.82％but also demonstrates exceptional stability,retaining 93.8％of its initial efficiency even after a 30-day aging test conducted under ambient air conditions in PSCs without encapsulation.These findings underscore the critical role of chlorine-substituent regulation in HTMs in ensuring the formation and maintenance of efficient and stable PSCs.
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