Enhanced charge extraction in carbon-based all-inorganic CsPbBr3 perovskite solar cells by dual-function interface engineering

Carbon-based all-inorganic CsPbBr3 perovskite solar cells (PSCs) have attracted growing interests due to low cost and excellent tolerances toward moisture, temperature, oxygen and ultraviolet light. However, carrier recombination of CsPbBr3 film and large energy level differences at CsPbBr3/carbon interface are still the most crucial problem for further enhancement of power conversion efficiency. In the current study, an intermediate energy level at CsPbBr3/carbon interface and CsPbBr3 film passivation are employed by coating hexane solution of CsPbBrxI3-(x) nanocrystals (NCs) on the perovskite layer. Through systematic study on interfacial engineering, it is found that CsPbBrxI3-x NCs with tunable energy level can remarkably reduce energy loss and hexane under passivation treatment can enlarge perovskite grain size as well as reduce trap state density. A champion power conversion efficiency of 9.45% is achieved for CsPbI3 NCs tailored all-inorganic CsPbBr3 PSC in comparison with 5.26% for NCs-free device, with the unencapsulated carbon-based CsPbBr3 PSC exhibiting remarkable long-term stability over 900 h in 80% relative humidity air atmosphere at 25 degrees C. This work provides an effective approach to promote charge extraction and reduce defect states density as well as enhance the performance of PSCs. (C) 2019 Elsevier Ltd. All rights reserved.