Porphyrin‐Based Simple and Practical Dopant‐Free Hole‐Transporting Materials for Efficient Perovskite Solar Cells Using TiO 2 Semiconductors

A new series of structurally simple and easily accessible hole‐transporting materials (HTMs) YZT1–YZT4 using porphyrin backbone is devised for high‐performance perovskite solar cells (PSCs) with and without the aid of doping. The YZT‐series HTMs have either push–push or push–pull type planar linear molecular geometry with substitution of linear or branched alkylamine. UV–vis absorption, photoluminance (PL) quenching experiments, and theoretical studies all suggest a different pattern of molecular packing induced by molecular geometry and/or substituted chains. Nonetheless, both types of porphyrin HTMs perform well in TiO 2 ‐based PSCs when doped YZT4 with a power conversion efficiency (PCE) of 14.95% and undoped YZT1 with a PCE of 13.10%. The results clearly reveal the potential for porphyrin‐based HTMs for use in dopant‐free PSCs.