Sustainable Planar Hole-Transporting Material-Free Carbon Electrode-Based Perovskite Solar Cells: Stability Beyond Two Years

Abstract

Past research demonstrating rapid increases in perovskite solar cells (PSCs) efficiency presented the challenge of achieving a balance between sustainability, efficiency, and cost for competitive commercialization. Current research focuses on effectively addressing these challenges. Conventional PSCs utilize hole-transporting materials (HTMs) and noble metal electrodes that are both unstable and costly, resulting in poor thermal stability and device instability. To overcome these issues, this study introduces unencapsulated planar HTM-free carbon-based PSCs (C-PSCs) fabricated through an all low-temperature process in ambient atmosphere conditions. The approach emphasizes simplicity and cost-effectiveness, featuring a single electron transporting layer and a one-step process to fabricate a perovskite layer [Cs0.17FA0.83Pb(I0.83Br0.17)3]. Carbon films, prepared with an ethanol solvent interlacing method and heat-press transfer method, serve as both hole transporting layers and electrodes. This simplified architecture leverages carbon material properties, achieving the highest PCE of 11.09% and outstanding self-life stability over 2 years (∼20,000 h) without encapsulation. Surprisingly, thermal and humidity stability testing under double 85 conditions aging (85% RH, 85 °C) showed an average 90% efficiency drop after 100 h. The degradation acceleration factors, calculated based on observed humidity and temperature dependence, predict intrinsic lifetimes of 22,816 h (2.6 years) in ambient air. Moreover, the scalable technique is demonstrated in 1.00 cm2 planar HTM-free C-PSCs on recycled FTO/TiO2-NPs substrates, showcasing remarkable performance under both 1 sun and LED illuminations. This approach reduces production costs, making PSCs renewable and sustainable, paving the way for cost-effective and eco-commercialized PSCs.