Understanding the effect of antisolvent on processing window and efficiency for large-area flexible perovskite solar cells

One-step method assisted by antisolvent is the most useful strategy to fabricate perovskite solar cells (PSCs) with high power conversion efficiency (PCE). Nevertheless, the narrow processing window and strict solvent ratio limit the preparation of large-area and uniform perovskite films. Herein, by thorough in-depth study of the interaction between solvents and antisolvents in the film preparation process, we found that the typical dimethylformamide solvent plays an important role in the antisolvent washing process. We demonstrate a solvent-antisolvent interaction model to understand the originality of the narrow processing window and solvent ratio based on chlorobenzene. Here, a green antisolvent ─ Ethyl Methyl Carbonate is introduced to widen a processing window from 2s to 35s and extend the volume ratio of dimethylformamide: dimethyl sulfoxide varying from 7:3 to 0:10 in the precursor solution. The obtained PSCs show a remarkable efficiency of 22.08% on rigid substrates, and 19.14% on flexible substrates. In a parallel effort, we demonstrate a uniform and large-area (6 × 6 cm2) flexible perovskite solar cell, exhibiting the highest PCE of 18.60%.