Structural and transport properties of doped CuI
Transparent thermoelectric materials are a group of promising wide band gap semiconductors in which their synergy of intrinsic properties can be used for room temperature energy harvesting. Currently, however, the leading thermoelectric materials are made of toxic and rare constituents, ultimately limiting their scalability. Copper(I) iodide, CuI, is a promising p-type transparent thermoelectric semiconductor that has the potential to overcome these limitations. CuI possesses a wide band gap and can be p-type doped intrinsically with copper vacancies, and extrinsically with chalcogenides, providing it with a unique combination of high transparency, electrical conductivity, and Seebeck coefficient. Because of these factors, it is the leading p-type compound for use in transparent thermoelectric generators and as an electrode for a plethora of optoelectronic applications.
It is the combination of the band structure, point defects, and carrier scattering processes within CuI that are the cause for its useful properties, and therefore, technological applicability. Understanding these processes will lead to improvements over its current limitations, which centrally rests in its still-moderate electrical conductivity. This work found that the adverse coupling between transport properties can be overcome by nanostructuring with noble gas ion implantation, while it was also found that oxygen and tellurium do not provide significant improvements for the electrical conductivity of CuI when already heavily-doped with copper vacancies.