Unveiling the dimensional effects of SnO2 quantum dots and nanoparticles on the interfacial properties of perovskite solar cells

Abstract

SnO2 is the most efficient and widely used electron conductor for perovskite solar cells (PSCs) due to its superior conductivity and high stability, however, the effect of SnO2's dimensions and sizes on the interfacial properties and device stability has often been ignored. Here, we investigate the relationship between device performance and electron conductors, including SnO2 quantum dots (SnO2 QD) and SnO2 nanoparticles (SnO2 NC). In contrast to SnO2 NC, SnO2 QD yields larger perovskite grains and high film uniformity, resulting in remarkable device efficiency and stability. Nonetheless, the device containing SnO2 QD exhibits a significant current-voltage hysteresis. By incorporating SnO2 QD and SnO2 NC to construct a bilayer structure, the hysteresis response and efficiencies of the devices have been drastically altered. PSCs based on SnO2 QDs exhibit a significant capacitive response at low frequencies and an exponential increase in capacitance at lower voltages, indicating significant charge accumulation at the interfaces. After being passivated with SnO2 NC in a bilayer structure, the wide depletion region at the high built-in potential provides a greater driving force for charge transfer, resulting in a significant reduction of hysteresis and an efficiency increase to >21%. This research provides insights into the significance of structural effects on electron conductors and will aid in enhancing the device performance of PSCs.