Interfacial crosslinking benzimidazolium enables eco-friendly inverted perovskite solar cells and modules

Interfacial engineering via controlled crosslinking at perovskite surface is of significance to address the interfacial loss in inverted perovskite solar cells (PSCs), while is unfortunately impeded by the unsatisfied interfacial charge extraction and transfer owing to the inherent low conductivity of the formed crosslinked network. We herein propose and validate a strategy of interfacial crosslinking benzimidazolium (ICB) that is capable of reducing the surface residual strain of perovskite and improving the interfacial carrier transfer, leading to a new benchmark of power conversion efficiency (PCE) up to 25.30 % in inverted PSCs, as well as 21.73 % in inverted PSC modules (6 × 6 cm²). Such the ICB network also results in sustainable PSCs and modules with superior stability even under various harsh conditions, e.g. suppressing lead leakage of PSCs with the rate of 83.6 %, maintaining the initial efficiency of 90 % after 1200 h of continuous heating at 85 °C, and 92.8 % of its pristine efficiency over 1200 h of continuous irradiation. We thus believe that present work demonstrates the potential of ionic molecules crosslinking at interfaces for high performance inverted PSCs.