A carbazole-based dopant-free hole-transport material for perovskite solar cells by increasing the molecular conjugation

Abstract Dopant-free hole-transport material (HTM) is essential to the long-term stability of the perovskite solar cells (PSCs). This study has introduced a novel carbazole-based dopant-free HTM via the simple ring-closing reaction without using the expensive catalyst. It has found that the merger of a higher rigid conjugated ring into the molecular geometry of HTM is an effective way to improve its charge extraction ability, hole mobility and phase thermal stability. Consequently, a power conversion efficiency (PCE) of 16.4% as well as a much-improved long-term stability have been achieved based on the as-prepared C302 dopant-free HTM.