A new D-A-D type benzodithiazole-based hole transport material for Sn-Pb perovskite solar cells with high efficiency and stability

While perovskite solar cells (PSCs) have recently experienced a rapid rise in power conversion efficiency (PCE), the environmental toxicity of lead still hinders the practical applications of lead-based PSCs. Tin-lead based PSCs has emerged as an effective solution, however, the hole transport material (HTM) for Sn-Pb PSCs have been rarely studied. Herein, a new D-A-D-type triarylamine benzodithiazole derivatives (TPA-BBT) with more appropriate energy band structure and higher hydrophobicity is synthesized and used as a HTM for inverted Sn-Pb PSCs. Impressively, it is found that TPA-BBT significantly improves the quality of perovskite films and reduces charge transport losses through passivating the uncoordinated Pb2+ and Sn2+ cations, yielding devices with a PCE of 15.85% under standard AM 1.5 G one sun illumination in the ambient air with an enhanced open-circuit voltage (VOC) from 0.696 V (control devices based on PEDOT: PSS) to 0.723 V. After 500 h storage in the ambient air (∼35% RH%), the PCE of TPA-BBT based PSCs remained 47% of the initial performance, while the control devices remained 25% for contrast. This work presents a promising direction toward the design of benzodithiazole derivatives used as HTM to improve the cell performance and stability of Sn-Pb PSCs.