Electronic Structure and Dynamics of Copper-Doped Indium Phosphide Nanocrystals Studied with Time-Resolved X-ray Absorption and Large-Scale DFT Calculations

Abstract

The recent development of time-resolved X-ray absorption spectroscopy (TR-XAS) has opened avenues for fundamental research on doped semiconductors. Reported herein are results on the successful doping of indium phosphide nanocrystals (NCs) with copper and subsequent characterization with time-resolved X-ray studies and large-scale density functional theory (DFT) calculations. The synthetic protocol that was based on the cluster seed method afforded control of both the doping level and the quantity of NCs produced in a batch. The stability of the colloidal dispersion allowed us to monitor the photophysical properties of copper guest ions with static and TR-XAS at the copper K-edge. These data reveal that copper captures a hole from the photoexcited InP NC, and relaxation to the ground state occurs via multiple timescales likely due to the presence of interior and surface-bound dopant ions as well as recombination with surface- and defect-trapped electrons. Large-scale DFT calculations reveal a striking dependence of the electronic structure on the ligand coating and other effects such as self-compensation.