Correlation of Electron Chemical Potential and Surface States in ZnO Nanoparticle Thin Films
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초록
내용
InP quantum dot (QD)-based light-emitting diodes (QLEDs) have shown remarkable progress since ZnO-based electron transport layers (ETL) were replaced with ZnMgO nanoparticles (NPs). Wide band gap MgO was alloyed with ZnO to elevate the conduction band to promote electron injection to InP cores. However, we observed the efficiency disparity between ZnO and ZnMgO despite their identical energy levels. In this study, we performed in-depth analysis on the electronic properties of ZnO and ZnMgO NPs. In organic semiconductor–Zn(Mg)O NPs junctions, ZnMgO exhibited smaller capacitance and larger built-in potential than those of ZnO. Considering that the surface state of ZnMgO NPs is more passivated, our observation can be understood that the surface states hinder the increment of electron chemical potential under the bias. Therefore, we conclude that the enhanced electron injection of ZnMgO is achieved by higher chemical potential of electrons established in the lower density of state system.