Surface-Modified Metallic Ti3C2Tx MXene as Electron Transport Layer for Planar Heterojunction Perovskite Solar Cells

MXenes are a large and rapidly expanding family of 2D materials that, owing to their unique optoelectronic properties and tunable surface termination, find a wide range of applications including energy storage and energy conversion. In this work, Ti 3 C 2 T x MXene nanosheets are applied as a novel type of electron transport layer (ETL) in low-temperature processed planar-structured perovskite solar cells (PSCs). Interestingly, simple UV-ozone treatment of the metallic Ti 3 C 2 T x that increases the surface Ti  O bonds without any change in its bulk properties such as high electron mobility improves its suitability as an ETL. Improved electron transfer and suppressed recombination at the ETL/perovskite interface results in augmentation of the power conversion efficiency (PCE) from 5.00% in the case of Ti 3 C 2 T x without UV-ozone treatment to the champion PCE of 17.17%, achieved using the Ti 3 C 2 T x film after 30 min of UV-ozone treatment. As the first report on the use of pure MXene layer as an ETL in PSCs, this work shows the great potential of MXenes to be used in PSCs and displays their promise for applications in photovoltaic technology in general.