Stars are Aligned: Triazatruxene Hole Transporting Material Hits the Sweet Spot to Reach 20% Efficiency of Perovskite Solar Cell

• The benchmarking of star-shaped organic semiconductors as HTMs for perovskite solar cells is presented. • The triazatruxene-based compounds are promising hole-transporting materials to enable 20% device efficiency without doping. • An optimal range of HOMO energy level of small-molecule hole transporting material for MAPbI3 is found experimentally. • Photoluminescence quenching is proportionally related to device efficiency in the absence of the intrinsic photoluminescence.