Abstract
Developing a one-step coating process for perovskite film formation is important for advancing perovskite solar cells (PSCs) toward practical applications. However, many high-efficiency PSCs reported to date still rely on conventional antisolvent-assisted processing. In this work, sulfolane (SF) was used as an additive in an antisolvent-free process to prepare efficient perovskite layers. The study shows that SF acts as a retardant to delay the formation of MAPbI3 grains. The results of XRD, 2D GIWAXS, and FTIR analyses suggest that SF interacts with the perovskite precursor and forms an intermediate phase, which contributes to the formation of high-quality perovskite films. Devices fabricated with the SF-treated films achieved a PCE of 22.2%, corresponding to a V oc of 1.2 V, a J sc of 23.7 mA/cm2, and an FF of 78.15%. The UPS, EIS, and ultrafast spectroscopy data explain the reduced recombination caused by SF treatment, leading to the high efficiency of the devices.