Boosted hole extraction in all-inorganic CsPbBr3 perovskite solar cells by interface engineering using MoO2/N-doped carbon nanospheres composite

Carbon-based all-inorganic CsPbBr3 perovskite solar cells (PSCs) have been a promising candidate in the field of photovoltaics due to its simple preparation process and excellent stability in air with high humidity. However, the power conversion efficiency (PCE) of such cells is still unsatisfactory to this day because of the large energy offset and poor hole extraction at the interface of CsPbBr3/carbon. Here, a MoO2/N-doped carbon nanospheres (NC) composite with high hole mobility and matched energy level is prepared by a facile one-step pyrolysis process and introduced into carbon-based all-inorganic CsPbBr3 PSC as a hole-transporting material (HTM) to enhance energy level alignment, interface contact and charge extraction as well as to passivate CsPbBr3 surface defects, realizing the reduction of energy loss and charge recombination. The optimal PSC based on MoO2/NC composite without encapsulation achieves a maximum PCE as high as 9.40% in comparison with 6.68% efficiency for the reference device and exhibits an outstanding long-term stability over 800 h in air atmosphere with 80% relative humidity. This work provides an effective approach to build high-performance and stable all-inorganic CsPbBr3 PSCs by introducing simple synthetic and efficient MoO2/NC composite inorganic HTM.