Heteroatom Effect on Star-Shaped Hole-Transporting Materials for Perovskite Solar Cells

Abstract

Three new star-shaped hole-transporting materials (HTMs) incorporatingbenzotripyrrole, benzotrifuran, and benzotriselenophene central cores endowedwith three-armed triphenylamine moieties (BTP-1, BTF-1, and BTSe-1, respec-tively) are designed, synthesized, and implemented in perovskite solar cells(PSCs). The impact that the heteroatom-containing central scaffold has on theelectrochemical and photophysical properties, as well as on the photovoltaicperformance, is systematically investigated and compared with their sulfur-richanalogue (BTT-3). The new HTMs exhibit suitable highest-occupied molecularorbitals (HOMO) levels regarding the valence band of the perovskite, whichensure efficient hole extraction at the perovskite/HTM interface. The molecularstructures of BTF-1, BTT-3, and BTSe-1 are fully elucidated by single-crystal X-raycrystallography as toluene solvates. The optimized (FAPbI3)0.85(MAPbBr3)0.15-based perovskite solar cells employing the tailor-made, chalcogenide-basedHTMs exhibit remarkable power conversion efficiencies up to 18.5%, which arecomparable to the devices based on the benchmark spiro-OMeTAD. PSCs withBTP-1 exhibit a more limited power conversion efficiency of 15.5%, with notice-able hysteresis. This systematic study indicates that chalcogenide-based deriva-tives are promising HTM candidates to compete efficiently with spiro-OMeTAD.