Tuning the crystal growth of perovskite thin-films by adding the 2-pyridylthiourea additive for highly efficient and stable solar cells prepared in ambient air

Abstract

Here, we report a rapid and simple process to prepare perovskite solar cells in ambient air by adding 2-pyridylthiourea in the precursor solution. 2-Pyridylthiourea can not only promote the conversion of 2-D PbI₂ to tetragonal CH₃NH₃PbI₃ crystals, but also improve the quality of the perovskite absorber layer via enhancing the uniformity and the size of the crystal grains. The perovskite solar cells with the addition of 2-pyridylthiourea at a concentration of 0.5 mg mL⁻¹ exhibited a remarkable overall power conversion efficiency (PCE) of 18.2%, which is among the highest PCE of CH₃NH₃PbI₃-based devices fabricated in ambient air. It also showed an 18% increase and less hysteresis compared with the cells without additives. Importantly, the devices with 2-pyridylthiourea show relatively better stability compared to reference devices when aged under ambient air of 55 ± 5% relative humidity in the dark and under 65 °C after 30 days. The presented results clearly show that 2-pyridylthiourea can be an additive candidate for tuning the morphology of perovskite thin films, which may be a new direction for large-scale production of PSCs.