Limits to Hole Mobility and Doping in Copper Iodide.

Area of Science:

• Materials Science
• Condensed Matter Physics
• Solid-State Chemistry

Background:

• Copper iodide (CuI) is a p-type transparent conducting material discovered over a century ago.
• Despite its long history, fundamental understanding of its charge transport mechanisms remains limited.
• Investigating CuI is crucial for advancing transparent conductive materials and optoelectronic devices.

Purpose of the Study:

• To elucidate the charge transport mechanisms in copper iodide (CuI).
• To identify limitations to hole mobility at various carrier concentrations.
• To explore the defect chemistry and potential of extrinsic dopants in CuI.

Main Methods:

• Utilized a variety of advanced modeling techniques to simulate charge transport properties.
• Employed hybrid functionals to investigate the defect chemistry of CuI.
• Analyzed scattering mechanisms, including ionized impurity and phonon scattering.
• Studied the impact of chalcogen (S, Se) doping on defect levels.

Main Results:

• Identified poor dielectric response causing ionized impurity scattering at high doping levels.
• Determined phonon scattering as the dominant mechanism at lower carrier concentrations.
• Predicted a phonon-limited hole mobility of 162 cm² V^-1 s^-1 at room temperature.
• Revealed copper vacancies as the primary source of charge carriers due to localized holes.
• Found S and Se dopants unlikely to be efficient electron acceptors due to deep transition levels.

Conclusions:

• Phonon scattering significantly limits hole mobility in CuI, particularly at lower carrier concentrations.
• The defect chemistry indicates copper vacancies are the main intrinsic source of p-type conductivity.
• Extrinsic doping with S or Se is unlikely to yield efficient n-type behavior in CuI.
• Understanding these mechanisms is vital for optimizing CuI-based devices.