In Situ Reconstructing the Buried Interface for Efficient CsPbI3 Perovskite Solar Cells

To CsPbI3 perovskite solar cells, defects from buried interfaces and improper energy band alignment can cause severe carrier recombination and hamper further enhancement in efficiency and stability. In this work, we develop an in situ strategy to reconstruct the buried interface for n-i-p typed CsPbI3 solar cells. This strategy is derived from an in situ exchange reaction between 18C6/Cs+ and Pb2+, leading to the formation of 18C6/Pb2+ in the CsPbI3 crystallization process (18C6: 18-crown-6 ether). The as-prepared 18C6/Pb2+ complex acts as a kind of molecular barrier to modify the TiO2/perovskite buried interface and passivate under-coordinated Pb2+ and iodide vacancies. Additionally, free Br- ions can diffuse into the lattice of the CsPbI3 film bottom, forming a front-surface field to further suppress carrier recombination. Based on this strategy, as high as 22.14% efficiency has been achieved, demonstrating one of the highest efficiencies of CsPbI3 perovskite solar cells to date. Besides, the modified cell can maintain 95% of its initial efficiency after 1500 h of MPP testing and 1500 h of long-term stability testing, exhibiting excellent operational stability.