Optical and electrical properties of ZnO nanocrystal thin films passivated by atomic layer deposited Al₂O₃

While colloidal semiconductor nanocrystal (NC) is preferred for use in solution-based optoelectronic devices, the large number of surface defects associated with its high surface-to-volume ratio degrades the optimal performance of NC-based devices due to the extensive trapping of free carriers available for charge transport. Here, we studied a simple and effective strategy to control the degree of passivation and doping level of solution-deposited ZnO NC films by infilling with ultra-thin Al₂O₃ using an atomic layer deposition (ALD) technique. According to various spectroscopic, microstructural, and electrical analyses, the ALD-Al₂O₃ treatment dramatically reduced the number of surface trap states with high ambient stability while simultaneously supplied excess carriers probably via a remote doping mechanism. As a consequence, the field-effect transistors built using the ZnO NC films with ALD-Al₂O₃ treatment for an optimal number of cycles exhibited significantly enhanced charge transport.