Extending the π-conjugation of a hole transport polymer to enhance the efficiency of perovskite solar cells

Abstract

The development of high-performance hole transport materials (HTMs) is crucial for n–i–p perovskite solar cells (PVSCs). Among various HTMs, electron donor (D)–electron acceptor (A) type conjugated polymers have emerged as promising candidates due to their tunable energy levels, high mobility and film formability through molecular design. Herein, two dopant-free polymeric HTMs, PBBT-T and PBBT-DT, have been designed and synthesized. By extending the π-conjugation in the polymer backbone, PBBT-DT exhibits a well-aligned HOMO energy level, improved backbone planarity and superior film formability. PBBT-DT-based PVSCs achieved a remarkable power conversion efficiency (PCE) of 19.12%, significantly higher than that of PBBT-T-based devices (11.02%). Furthermore, the hydrophobicity of PBBT-DT ensured excellent device stability to the devices, which retained 93% of their initial PCE after 30 days under ambient conditions. This work provides a useful strategy for developing dopant-free polymeric HTMs, which simultaneously enhance the efficiency and long-term stability of perovskite solar cells.