Improved Comprehensive Photovoltaic Performance and Mechanisms by Additive Engineering of Ti 3 C 2 T x MXene into CsPbI 2 Br.

CsPbI 2 Br is promising in the application of perovskite solar cells (PSCs) owing to its reasonable bandgap and good thermal stability. However, the reported power conversion efficiency (PCE) of the CsPbI 2 Br solar cells is still much lower than that of the organic-inorganic hybrid PSCs, mainly due to relatively poor CsPbI 2 Br crystal quality. Herein, additive engineering to the photoactive layer of CsPbI 2 Br using the Ti 3 C 2 T x MXene nanosheets is reported. Thanks to the improved crystallinity/reduced defect density, together with the formation of the Schottky junction between the MXene nanosheets and CsPbI 2 Br, enhanced separation and transfer of the photogenerated electron-hole pairs can be achieved for optimal MXene addition. A simple device configuration of ITO/SnO 2 /Ti 3 C 2 T x -added CsPbI 2 Br/P3HT/Ag can thus deliver a significantly boosted PCE of 15.10%, i.e., a ∼16.69% relative increment compared with that (12.94%) of the control device without adding MXene. In addition, the enhanced humidity resistance is achieved for the MXene-added CsPbI 2 Br layers.