Pure 2H phase MoSe2 nanosheets promote the formation of a porous PbI2 film and modulate residual stress for highly efficient and stable perovskite solar cells

Abstract

The above 25% certified efficiency had been achieved for perovskite solar cells (PSCs) with regular n–i–p device architecture based on two-step processes in recent years. However, the perovskite films prepared by two-step processes still have an incomplete PbI₂ reaction, poor crystallization quality and residual stress. Herein, an excellent strategy, i.e. introducing 2D MoSe₂ nanosheets as additives into PbI₂ precursor solution in the first step of two-step processes, is proposed to increase the conversion of PbI₂ and improve crystallinity as well as reduce residual stress simultaneously. It is revealed that MoSe₂ nanosheets prompt the formation of a porous PbI₂ film and then achieve a high quality perovskite film. Interestingly, MoSe₂ nanosheets play the role of a “lubricant” to relax residual stress. In addition, MoSe₂ nanosheets also result in a more suitable energy-level alignment at the perovskite/electron transport layer interface. Consequently, the average power conversion efficiency (PCE) of 21.76% and the highest PCE of 22.80% are achieved upon incorporating 2D MoSe₂ nanosheets, which are greatly improved compared to the average PCE of 19.40% and the highest PCE of 20.92% for the control PSCs. Besides, the MoSe₂-doped PSC could maintain 80% of its initial efficiency under 15–20% RH at room temperature for 1000 hours in air. This work not only provides a facile and efficient method to increase the PCE and stability of PSCs but also reveals the application potential of 2D MoSe₂ in PSCs and other optoelectronic devices.