Efficient perovskite solar modules with an ultra-long processing window enabled by cooling stabilized intermediate phases

Abstract

Perovskite solar cells (PSCs) have shown promising progress in efficiency and stability, but their application needs further development from small-area cell to large-area module. Fabricating solar cell modules in large-area substrate takes a longer time to deposit and process the thin film than small area devices. Therefore, it is required to expand the processing window of the solution process. Here, we showed that combining N-methyl-2-pyrrolidone solvent with a cooling strategy can generate more stable FA-based perovskite intermediates in two-step deposition, realizing a longer annealing window. The power conversion efficiency (PCE) of 25.21% for small-area devices (0.045 cm2) and 23.60% for large-area devices (1.00 cm2) were achieved. It is found that cooling the intermediate phase at a temperature close to 0°C can suppress the formation of δ-phase FAPbI3 and expand the annealing window by 20-fold (from 9 min to 180 min). With the cooling strategies, we have successfully fabricated uniform perovskite films in large area of 45 cm2. PSC mini-modules made by this method achieved state-of-the-art efficiencies of 22.34% and certified efficiency of 21.51%. More importantly, even with an annealing delay time of 180 min, the modules attain decent PCE of 20.89%, showing an ultra-long process window for fabricating efficient PSCs. Our strategy of stabilizing the perovskite intermediate phase brings great flexibility to the large-scale production of perovskite solar modules.