Highly efficient and cost-effective carbon paper electrode for inverted perovskite solar cells

Abstract

Perovskite solar cells (PSCs) are among the most promising photovoltaic technologies, with their power conversion efficiency (PCE) rising from 3.8 % in 2009 to 26.95 % in 2025. However, their commercialization remains hindered by challenges such as the high cost of noble metal back-contacts. Finding affordable alternatives for back-contacts is therefore a key research focus. Carbon-based materials have attracted growing interest due to their abundance, low cost, chemical stability, electronic conductivity, sustainability, and suitability for largescale deposition. In this work, the effective use of carbon paper (CP) as a back-contact in inverted PSCs was demonstrated. To facilitate charge extraction, a thin metal interlayer, consisting of ca. 7 nm of gold (Au) or silver (Ag), was introduced between the electron transport layer and the CP. Five different CPs were tested, yielding PCEs of 6.35 % and 8.65 % for devices incorporating 7 nm Au + CP and 7 nm Ag + CP, respectively. To further enhance charge extraction, the impact of a thermally evaporated molybdenum trioxide-doped gold (7 nm Au: MoO3) was explored, resulting in enhanced interface quality and reduced recombination losses. A champion device with a PCE of 15.6 % was achieved, making one of the highest reported values for carbon-based inverted PSCs.