Carbon nanotubes as hole-selective contacts for high-efficiency full-area GaAs hybrid heterojunction solar cells

Organic hybrid heterojunction solar cells (HJSCs) based on PEDOT:PSS have attracted significant attention due to their excellent photovoltaic performance. However, the complex carrier transport layer, intricate cell fabrication processes and their high-cost are not proportional to the optimization of cell performance. In this work, we demonstrated a facile annealing process lasting only a few seconds to prepare a high-performance Nafion/PEDOT:PSS (NP) hole transport layer (HTL) and its GaAs hybrid heterojunction. By introducing Nafion, the GaAs/NP HJSC achieves a competitive power conversion efficiency (PCE) of 15.77% thanks to the improved wettability, conductivity and carrier mobility of the HTL. Additionally, a thin and transparent carbon nanotube (CNT) film was introduced as the top electrode for the full-area GaAs/NP hybrid HJSC. The novel design of the NP HTL and full-area light absorption open a new avenue for the widespread application of heterojunction photovoltaic technologies. A schematic of the full-area GaAs/NP hybrid HJSC configuration and the energy band diagram of its heterojunction upon illumination.