20.8% slot-die coated MAPbI3 perovskite solar cells by optimal DMSO-content and age of 2-ME based precursor inks
Solar cells incorporating metal-halide perovskite (MHP) semiconductors are continuing to break efficiency records for solution-processed solar cell devices. Scaling MHP-based devices to larger area prototypes is a crucial step towards commercialization. This requires the development and optimization of scalable process technology for these devices. Here, we demonstrate a maximum power conversion efficiency (PCE) of 20.83% for slot-die coated gas-quenched small-area methylammonium lead iodide
... nium lead iodide (MAPbI3) devices. Our ink is based on 2-methoxy-ethanol (2-ME) with the strongly coordinating solvent dimethyl-sulfoxide (DMSO) added in small amounts. We found that the amount of DMSO, as well as the age of the precursor solutions, are determining factors in achieving highly efficient and reproducible devices. Through in-depth insight into the film formation process as a function of DMSO content from in-situ X-ray diffraction experiments, we found that just the right amount of DMSO favorably affects thin film growth. Adding 11.77 mol% of DMSO prevents the formation of a crystalline intermediate phase related to MAPbI3 and 2-ME (MAPbI3 -2-ME), reported here for the first time, and inducing the formation of some (DMSO)2MA2Pb3I8 intermediate phase. These results demonstrate that ink composition and process control are critical to enable reproducible large-scale manufacturing of MHP-based devices for commercial applications.