Limits to Hole Mobility and Doping in Copper Iodide

Over one hundred years have passed since the discovery of the p-type transparent conducting material copper iodide, predating the concept of the electron-hole itself. Supercentenarian status notwithstanding, little is understood about the charge transport mechanisms in CuI. Herein, a variety of modeling techniques are used to investigate the charge transport properties of CuI, and limitations to the hole mobility over experimentally achievable carrier concentrations are discussed. Poor dielectric response is responsible for extensive scattering from ionized impurities at degenerately doped carrier concentrations, while phonon scattering is found to dominate at lower carrier concentrations. A phonon-limited hole mobility of 162 cm(2) V-1 s(-1) is predicted at room temperature. The simulated charge transport properties for CuI are compared to existing experimental data, and the implications for future device performance are discussed. In addition to charge transport calculations, the defect chemistry of CuI is investigated with hybrid functionals, revealing that reasonably localized holes from the copper vacancy are the predominant source of charge carriers. The chalcogens S and Se are investigated as extrinsic dopants, where it is found that despite relatively low defect formation energies, they are unlikely to act as efficient electron acceptors due to the strong localization of holes and subsequent deep transition levels.

Automated summary

This study investigated the charge transport properties and defect chemistry of copper iodide (CuI) using various modeling techniques. It discussed the limitations to charge transport mechanisms at different carrier concentrations and their implications for future device performance. The research found that poor dielectric response led to extensive scattering from ionized impurities at high carrier concentrations, while phonon scattering dominated at lower concentrations.