Locally Supersaturated Inks for a Slot-Die Process to Enable Highly Efficient and Robust Perovskite Solar Cells

Perovskite solar cells (PSCs), which debuted with a lot of attention based on high efficiency, are establishing as one of the most promising thin-film photovoltaic technologies. Currently, research for upscaling and commercialization through eco-friendly solvent and process systems is being attempted. This study introduces for the first time a rheological engineering-based locally supersaturated perovskite ink (LSPI) strategy for slot-die process-based PSC fabrication suitable for roll-to-roll continuous processes. Here, for the greenable slot-die process, a perovskite precursor ink composed of a low-toxic dimethyl sulfoxide (DMSO) single solvent is used and a small amount of 1,2-dichlorobenzene (DCB) is utilized as a modulator to control the rheological properties of the ink. The addition of DCB lowers the high surface tension of the DMSO-based perovskite precursor ink to suit the slot-die process, enabling uniform wet film formation, and produces locally supersaturated colloids, i.e., perovskite seeds, that help growth into dense and large grains by heterogeneous nucleation with low Gibbs-free energy. As a result, the LSPI enables slot-die coating-based PSCs with an efficiency of 20.61% (active areas of 0.1 cm²), which allow high efficiencies of 18.66% and 17.66% (active areas of 2.7 and 8.64 cm²) to be achieved in scale-up to minimodules, respectively.