Positional isomer engineering of carbazole-based hole transport materials for perovskite solar cells

Abstract

The development of hole transport materials (HTMs) is crucial for advancing the efficiency and long-term stability of perovskite solar cells (PSCs). To address the limitations of the conventional Spiro-OMeTAD, such as its complex synthesis and high production cost, we designed two novel carbazole-based HTMs, TCBZ-36 and TCBZ-27, through engineering the substitution position of the tricarbazole core. The 2,7-substitution of TCBZ-27 was found to significantly enhance hole mobility and conductivity while improving film morphology compared with its 3,6-substituted counterpart, TCBZ-36. These superior properties translated into outstanding device performance, achieving a champion power conversion efficiency (PCE) of 25.2% (V_oc = 1.16 V, J_sc = 26.2 mA cm⁻², and FF = 83.5%), along with exceptional storage stability in ambient environment. This study presents a cost-effective molecular design strategy that can simultaneously enhance the efficiency and stability of perovskite photovoltaic devices.