Ultrafast carrier dynamics and insights in defect mechanism of p-type colloidal ZnO QDs

In this study, we place a strong emphasis on understanding the ultrafast dynamics of carrier recombination pathways in p-type ZnO, especially in the midgap region. Synthesizing and controlling the properties of p-type ZnO remains a pivotal yet challenging task for numerous optoelectronic and spintronic applications due to intrinsic midgap (defect) states. Through an advanced sol-gel process, we have successfully produced ZnO quantum dots (QD), eliminating unreacted molecules that decrease the excitonic emission. This refined method supports the generation of ZnO with p-type characteristics, primarily attributed to zinc vacancies in oxygen-rich scenarios. Notably, our analysis across timescales from femtoseconds to microseconds unveiled carrier lifetimes at room temperature, and associated long-lasting carriers with zinc vacancy defects, corroborating the p-type nature of our synthesized ZnO QDs.