All room-temperature processing efficient planar carbon-based perovskite solar cells

Carbon based perovskite solar cells (C–PSCs) with long-term stability and low cost have been considered as a competitive candidate for further actual applications. Generally, the preparation of semiconductor oxide electron transport layer and perovskite involves high-temperature annealing procedure for abundant light absorption as well as efficient charge transport, which limits its flexible application. Herein, we develop an all room temperature processing high-efficiency planar C-PSCs that utilizes SnO2 as electron transport layer and a cheap polymer i.e. polyethylene glycol (PEG) as the interface passivation layer to reduce the defect state density of perovskite and facilitate valid charge transfer from perovskite to carbon. The resultant planar C-PSC devices achieve a power conversion efficiency (PCE) of 14.5% comparable to the conventional C-PSCs with annealing process, about 50% higher than that based on bare C-PSC devices without PEG. The room-temperature processing C–PSCs exhibits excellent stability, retaining around 90% of the initial PCE after being stored in air for 20 days. Furthermore, this room-temperature process is extended to the flexible C–PSCs, achieving a PCE over 10%. This work offers a facile room-temperature approach to reliably prepare efficient C–PSCs via interface modification.