Open-air printing of Cu2O thin films with high hole mobility for semitransparent solar harvesters

Abstract

Cu₂O is a promising p-type semiconductor for low-cost photovoltaics and transparent optoelectronics. However, low-cost and low-temperature fabrication of Cu₂O films with good transport properties remains challenging, thus limiting their widespread adoption in devices. Here, we report Cu₂O thin films of 20–80 nm thickness with hole mobility up to 92 cm²V⁻¹s⁻¹ using atmospheric-pressure spatial atomic layer deposition at temperatures below 260 °C, from a copper (I) hexafluoro-2,4-pentanedionate cyclooctadiene precursor. Raman spectroscopy indicates the presence of copper split vacancies and shows that the high hole mobility can be correlated to a low concentration of shallow acceptor defects. The optical bandgap of deposited films can be tuned between 2.08 eV and 2.5 eV, depending on the deposition temperature. All-oxide semitransparent Cu₂O/ZnO solar harvesters are fabricated, showing efficiency values comparable to devices that incorporate much thicker Cu₂O layers. Our work provides a promising approach towards cost-efficient, all-oxide solar harvesters, and for other (opto)electronic devices.

Semiconducting Cu₂O is attractive for photovoltaic and optoelectronic devices, though balancing high hole mobility with low-cost fabrication is challenging. Here, Cu₂O thin films with high hole mobility of 92 cm²V⁻¹s⁻¹ are deposited in air, and applied in a semi-transparent solar harvester.