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.
Highlights
Cu2O is a promising p-type semiconductor for low-cost photovoltaics and transparent optoelectronics
atomic layer deposition (ALD) precursors must be volatile to ensure proper film deposition, and this is, even more, the case for systems working at atmospheric pressure, such as the Atmospheric-pressure spatial atomic layer deposition (AP-SALD) one used here
Our report shows that solid precursors with relatively low volatility (0.1 mm Hg) can be used in atmospheric SALD systems to deposit intrinsic materials after proper optimization of the system and the deposition parameters. (While there have been two reports involving the use of a solid precursor in SALD, namely trimethylindium [In(CH3)[3], (TLIn)], used to deposit InxGayZnzO and InxZn1-xO45,46 this precursor has a vapor pressure of 5 mm Hg, almost two orders of magnitude higher than the Cu precursor used here, and was used only to introduce doping)
Summary
Cu2O is a promising p-type semiconductor for low-cost photovoltaics and transparent optoelectronics. The difficulty in obtaining intrinsic Cu2O thin films having high hole mobility using low temperature, atmospheric-pressure approaches have limited the application of such methods to Cu2O-based devices. To harness the full potential of Cu2O and other Cubased materials, innovative low temperature and scalable deposition methods that are capable of yielding Cu2O thin films with physical properties equivalent to those obtained with hightemperature and/or vacuum-based physical methods are needed. In this context, atomic layer deposition (ALD) is gaining momentum in the last years due to its ability to offer good quality materials at low temperatures (
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