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

Carbon-based all-inorganic CsPbBr 3 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 CsPbBr 3 film and large energy level differences at CsPbBr 3 /carbon interface are still the most crucial problem for further enhancement of power conversion efficiency. In the current study, an intermediate energy level at CsPbBr 3 /carbon interface and CsPbBr 3 film passivation are employed by coating hexane solution of CsPbBr x I 3-x nanocrystals (NCs) on the perovskite layer. Through systematic study on interfacial engineering , it is found that CsPbBr x I 3-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 CsPbI 3 NCs tailored all-inorganic CsPbBr 3 PSC in comparison with 5.26% for NCs-free device, with the unencapsulated carbon-based CsPbBr 3 PSC exhibiting remarkable long-term stability over 900 h in 80% relative humidity air atmosphere at 25 °C. This work provides an effective approach to promote charge extraction and reduce defect states density as well as enhance the performance of PSCs.