Optimizing SnO2 Quantum Dot Precursor Solutions for Perovskite Solar Cells with Reduced Hysteresis

In recent years, SnO2 quantum dots (QDs) have been widely used for preparing the electron-transport layer within perovskite solar cells (PSCs). However, the fabricated devices exhibit an evident hysteresis unless interlayer materials are introduced to passivate or prevent the formation of trap states at the SnO2–perovskite interface. Herein, the use of the zwitterion 3-(1-pyridinio)-1-propanesulfonate (PPS) as additive inside the SnO2 QDs solution is proposed. The results highlight that the PPS plays a multifunctional role by accelerating the synthesis of the QDs, enhancing the electron transfer and passivating defects at the SnO2–perovskite interface. The resulting PSCs with SnO2 QDs incorporating PPS exhibit a remarkable reduction in hysteresis index (HI) compared to those prepared with thiourea or without any additives. This reduction in HI suggests that PPS serves as a cost-effective alternative additive for SnO2 QDs preparation, eliminating the need for additional interlayers or expensive additives.