A novel carbon electrode for up-scaling flexible perovskite solar cells

Carbon-based perovskite solar cells (C-PSCs) possess the beneficial attributes of a simple fabrication process, superior stability, and cost-effectiveness. However, flexible C-PSCs have a relatively lower device efficiency when compared to rigid C-PSCs, the reason for which is mainly the poor interface contact between the hole transporting layer (HTL) and the carbon electrode. Herein, a novel carbon electrode (C-rCP) grafted by reduced graphene oxide (rGO)-carbon quantum dots (CQDs)-polyethylene glycol (PEG) composites, is prepared using a modified, room-temperature ethanol solvent interlacing process with a magnetic stirring. Owing to a simple press transfer method used, C-rCP is well suited as counter electrodes of C-PSCs due to their lower sheet resistance; higher density; excellent bendability; suitable thickness; great self-adhesion; and appropriate energy band arrangement that can improve carrier transport, as well as enhance the HTL/carbon interface contact. The best flexible C-PSCs with an area of 0.04 cm2 achieve a power conversion efficiency (PCE) of 12.34%. Furthermore, PCEs of 8.80% and 21.61% based flexible C-PSCs with an area of 1.00 cm2 are achieved under 1 sun and 1000 lux illuminations, respectively. The introduction of this C-rCP offers an effective method of up-scaling and developing flexible and rigid C-PSCs for future eco-commercialization.