Tuning the ionic–electronic charge transport in CsPbBr3 nanocrystals through the interplay of quantum confinement and stoichiometry engineering

Abstract

All-inorganic cesium lead bromide (CsPbBr3) nanocrystals (NCs) have established themselves as an emerging semiconductor for next-generation optoelectronic technologies due to their unique combination of properties, such as near unity photoluminescence quantum yields, narrow color pure emission, and exceptional defect tolerance. Although size-dependent optical signatures of these NCs are well reported, the complexity of mixed ionic–electronic transport remains largely unexplored. In this study, we provide a comprehensive analysis of size-dependent charge transport by decoupling ionic and electronic transport dynamics through carefully designed transient current and space charge limited current measurements. By employing NCs of different sizes ranging from 5.6–11.3 nm in thin films, we provide a comprehensive understanding of quantum confinement effects and related synthetic chemistry. Contrary to the conventional understanding that nano confinement induces bandgap broadening and adversely affects the charge transport, our results demonstrate that the smallest NCs, t-CsPbBr3, synthesized using an organobromide precursor tribromoisocyanuric acid (TBIA), exhibit the most efficient transport characteristics. Moreover, device fabricated from t-CsPbBr3 exhibits the lowest hole activation energy ( Eahole = 78 meV) and the highest barrier for vacancy-mediated ion migration ( Eaion = 370 meV). The origin of this improved transport can be attributed to a synergistic interplay of precursor chemistry, defect suppression, and partially to quantum confinement. This work paves the way for perovskite-based efficient quantum devices, where chemically tailored synthesis enables access to the strong quantum confinement regime and promotes efficient charge transport through suitable precursor chemistry.