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

Abstract

The development of high-performance hole transport materials (HTMs) is crucial for the 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 its 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 for perovskite solar cells.