N-Methyl-2-pyrrolidone driven solvent engineering of hybrid perovskite solar cells fabricated under air ambient conditions

The efficiency and stability of perovskite solar cells (PSCs) are highly affected by their morphological properties, including grain size, crystal orientation, and perovskite film coverage. Solvent engineering has been recognized as a key strategy for controlling the film formation process and achieving optimized morphologies. Herein, we have explored solvent engineering using N-Methyl 2-pyrrolidone (NMP) for mixed cation and mixed halide-based PSCs to investigate the impact on device performance. To optimize the NMP concentration, four different precursor solutions with NMP quantities 0 mu L (N0), 20 mu L (N20), 40 mu L (N40), and 60 mu L (N60) were prepared by partially replacing DMSO in a triple solvent system (i.e., DMSO, DMF, and NMP). Optimum amount of NMP in the precursor solution leads to the formation of better uniformity, coverage, and compact film with larger grains. By incorporating a modification with the N40 precursor solution, the champion device fabricated under air ambient achieved an efficiency of 21.54 %. The optimized devices exhibited remarkable stability, maintaining an efficiency above 91 % even after 1500 h of storage in the dark under ambient. Thus, this study provides the pathway for improving the device performance and stability of PSCs by utilizing the solvent engineering approach.