Interfacing Pristine C60 onto TiO2 for Viable Flexibility in Perovskite Solar Cells by a Low-Temperature All-Solution Process

A low-temperature solution-processed strategy is critical for cost-effective manufacture of flexible perovskite solar cells (PSCs). Based on an aqueous-processed TiO2 layer, and conventional fullerene derivatives replaced by a pristine fullerene interlayer of C-60, herein a facile interface engineering for making all-solution-processed TiO2/C-60 layers in flexible n-i-p PSCs is reported. Due to the improvement of the perovskite grain quality, promotion of interfacial charge transfer and suppression of interfacial charge recombination, the stabilized power conversion efficiency for the flexible PSCs reaches as high as 16% with high bending resistance retention (approximate to 80% after 1500 cycles) and high light-soaking retention (approximate to 100% after 100 min). In addition, the stabilized efficiency is over 19% for the rigid TiO2/C-60-based PSCs. The present work with the facile low-temperature solution process renders the practicability for high-performance flexible PSCs applied to wearable devices, portable equipment, and electric vehicles.