Molecular engineering of methoxy-substituted terthienyl core unit based hole transport materials for perovskite solar cells

Hole transport materials (HTMs) are an integral part of highly efficient perovskite solar cells (PSCs). Although the traditional HTM Spiro-OMeTAD achieves excellent performance, its high cost limits its future large-scale application during commercialization of PSCs. Therefore, it is essential to develop low-cost and efficient alternative HTMs. Herein, we successfully synthesize two novel HTMs DTP-1 and DTP-2 by employing methoxy-substituted terthienyl (DTP) as the core unit and adjusting the electron donors. Research indicates that the introduction of methoxy groups on the core unit enhances its electron donating ability; thus, the capping groups with slightly lower electron donating ability should be adopted to get well-matched energy levels. After optimization, the best-performing power conversion efficiency (PCE) of DTP-1 based PSCs is 21.1%, which is much higher than those of PSCs based on DTP-2 (15.6%) and THP-1 (20.5%). Furthermore, under the conditions of RH 30-45% and room temperature, the DTP-1-based devices maintain 80.5% of the initial PCE after aging for 840 h, which is better than those of DTP-2 (22.0%) and THP-1 (71.5%).