PNNL

Abstract

The synthesis and control of properties of p-type ZnO is crucial for a variety of optoelectronic and spintronic applications, however, it remains challenging due to the control of intrinsic midgap (defect) states. In this study, we demonstrate a synthetic route to yield colloidal ZnO quantum dots (QD) via an enhanced sol-gel process that effectively eliminates the residual intermediate reaction molecules which would otherwise weaken the excitonic emission. This process supports the creation of ZnO with p-type properties or compensation of inherited n-type defects, primarily due to zinc vacancies in oxygen-rich conditions. The in-depth analysis of carrier recombination in the midgap across several timescales reveals microsecond carrier lifetimes at room temperature which are expected to occur via zinc vacancy defects, supports the promoted p-type character of the synthesized ZnO QDs.