Electron Extraction Optimization for Carbon‐Based Hole‐Conductor‐Free Perovskite Photovoltaics With Record 1.41 V VOC

Carbon-based CsPbI2Br perovskite solar cells (PSCs) free of a hole-transport layer (HTL) have emerged as promising photovoltaics due to their low processing cost and superior stability. However, the voltage deficit resulting from inefficient carrier extraction causes insufficient power conversion efficiency (PCE), severely hindering their progress. Here, a gradient electron energy level modulation strategy proves effective in reducing voltage losses through the rapid extraction of photogenerated electrons. This process enhances carrier separation/collection and reduces recombination at the back contact, thereby achieving high-performance photovoltaics. It is demonstrated that the front electron extraction, equally critical as the prevailing back perovskite/carbon contact, accounts for the significant contributing factor of voltage deficit in carbon-based HTL-free PSCs. The resulting PSCs deliver a record open-circuit voltage (VOC) of 1.41 V and a PCE of 17.42% and retain more than 92% of their initial efficiency after 1, 000 h. These results highlight the significant potential of carbon-based HTL-free perovskite photovoltaics.