A doctor-blading process for the fabrication of triple-cation halide-perovskite thin films using eco-friendly solvents under ambient conditions is demonstrated. An eco-friendly perovskite precursor composed of γ-butyrolactone (GBL)/dimethylsulfoxide (DMSO)/isopropanol (IPA) mixture is used. The coordination between PbI2 and DMSO effectively suppresses the perovskite crystal grow rate which results in a dense and uniform film. However, the intermediate DMSO–PbI2 phase residual has a negative impact on the perovskite film quality. The amount of residues, the trap-state defect density, the perovskite film uniformity, and the device performance can be considerably affected by adding IPA in the precursor due to its capability to facilitate DMSO evaporation. Heating post-treatment on the top side of the film homogenizes the evaporation rate of the air–liquid surface which leads to a larger grain size and unbroken film. The device using perovskite solution with GBL/DMSO/IPA mixture as solvent achieves a decent power conversion efficiency (PCE) of 12.3% with a Voc of 1.01 V and a Jsc of 19.3 mA cm−2. The bare device retains 76.5% of its original PCE after 25 days under ambient environment at 35 °C, with 35–40% relative humidity. A large-size device with an active area of 2.4 cm2 delivers a PCE of 8.52%.
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