High-Power and Flexible Indoor Solar Cells via Controlled Growth of Perovskite Using a Greener Antisolvent

Flexible perovskite solar cells attract significant attention because of their high accessibility in device fabrication, inexpensive fabrication process, and remarkable power conversion efficiency (PCE). Solvent engineering has been an important protocol for synthesizing high-quality perovskite thin films. Toxic antisolvents such as chlorobenzene (CB) are necessary to obtain desirable film morphologies. This study proposes a novel green antisolvent, butyl acetate (BA). It exhibits low toxicity, but its physical properties are similar to those of CB. The difference between the solubility parameters of antisolvents and dimethyl sulfoxide (DMSO) determines the volume of residual DMSO within perovskite–DMSO complexes. During spin coating, BA leaves excess DMSO more effectively than CB because of larger differences in solubility parameters, facilitating the gradual nucleation and growth of perovskite grains. The resulting enlarged grains (>1 μm) reduce trap density and improve charge carrier mobility, resulting in a significant enhancement in the device performance (PCE = 19.78%) and environmental stability (PCE retention of 97.4% after 1000 h). Furthermore, highly efficient and flexible devices are available as indoor light energy harvesters. At 400 lx of a white light-emitting diode, a bent device with a bending radius of 10 mm exhibits a remarkable maximum power density of 0.063 mW cm–2 and PCE of 23.33%.