Detailed Investigation of Quantum Confinement Effects in MAPbI3 Perovskite Quantum Dots through Cyclic Voltammetry and Ultraviolet Photoelectron Spectroscopy

Abstract

A detailed investigation of quantum confinement effects in MAPbI 3 perovskite quantum dots (PQDs) is essential for understanding size-dependent modifications in electronic structure, optical transitions, and carrier dynamics. In this study, we systematically investigate the sizequantization effect in MAPbI 3 PQDs using cyclic voltammetry (CV) and ultraviolet photoelectron spectroscopy (UVPS). PQDs of controlled sizes were synthesized via a ligandassisted reprecipitation (LARP) method by varying the concentration of n-octylamine, yielding diameters in the strong to intermediate confinement system. CV measurements enabled direct determination of valence and conduction band-edge positions under ambient conditions. Our results reveal a pronounced upward shift in the conduction band (LUMO) with decreasing particle size, while the valence band (HOMO) exhibits a comparatively smaller shift. This asymmetric band-edge modulation aligns with quantum confinement models, where the extent of energy level shift is inversely related to the carrier effective mass. The larger shift in LUMO is attributed to the lower effective mass of electrons compared to holes in MAPbI 3 .Additionally, a strong correlation between the electrochemical bandgap and optical bandgap was observed, emphasizing the role of increased Coulombic interaction in smaller PQDs. These findings advance the understanding of quantum size effects in MAPbI 3 PQDs and highlight the efficacy of CV as a reliable tool for probing size-dependent electronic structures in PQDs.