Carbon Nanotube Based Inverted Flexible Perovskite Solar Cells with All‐Inorganic Charge Contacts

Abstract Organolead halide perovskite solar cells (PSC) are arising as promising candidates for next‐generation renewable energy conversion devices. Currently, inverted PSCs typically employ expensive organic semiconductor as electron transport material and thermally deposited metal as cathode (such as Ag, Au, or Al), which are incompatible with their large‐scale production. Moreover, the use of metal cathode also limits the long‐term device stability under normal operation conditions. Herein, a novel inverted PSC employs a SnO 2 ‐coated carbon nanotube (SnO 2 @CSCNT) film as cathode in both rigid and flexible substrates (substrate/NiO‐perovskite/Al 2 O 3 ‐perovskite/SnO 2 @CSCNT‐perovskite). Inverted PSCs with SnO 2 @CSCNT cathode exhibit considerable enhancement in photovoltaic performance in comparison with the devices without SnO 2 coating owing to the significantly reduced charge recombination. As a result, a power conversion efficiency of 14.3% can be obtained on rigid substrates while the flexible ones achieve 10.5% efficiency. More importantly, SnO 2 @CSCNT‐based inverted PSCs exhibit significantly improved stability compared to the standard inverted devices made with silver cathode, retaining over 88% of their original efficiencies after 550 h of full light soaking or thermal stress. The results indicate that SnO 2 @CSCNT is a promising cathode material for long‐term device operation and pave the way toward realistic commercialization of flexible PSCs.