Slot-die coating of electron transport layers for perovskite solar cells using water and butanol-based tin oxide dispersions

Lead halide perovskite photovoltaics have shown an impressive efficiency increase over the past decade. Making this technology industrially viable requires precise optimization of every single deposition step. Here we used slot-die coating, a promising scalable deposition technique to enable large scale deposition. We demonstrate the challenges in developing high-quality slot-die coated tin oxide (SnO2) films, suited as electron selective layers in perovskite solar cells. We studied the film quality of two commercially available colloidal SnO2 dispersions by controlling pump rate, coating speed and temperature of the indium tin oxide substrates (ITO). The water-based dispersion was more difficult to control, but resulted in better perovskite solar cell performance than the butanol-based dispersion. Hysteresis in J-V curves from the water-based tin oxide dispersion was reduced by potassium fluoride addition. A maximum power conversion efficiency of 17.5% was achieved for MAPbI3-based solar cells by careful optimization of the deposition parameters. Slot-die coated tin oxide films are suited as electron transport layers in large-scale perovskite solar cells.