Stability of sputter deposited cuprous oxide (Cu2O) subjected to ageing conditions for photovoltaic applications

Abstract

Among various metal oxide p-type semiconductors, cuprous oxide (Cu2O) stands out as a nontoxic and abundant material, which also makes it a suitable candidate as a low-cost absorber for photovoltaic applications. However, the chemical stability of the absorber layer is critical for the solar cell lifetime, in particular, for Cu-based materials, concerning to its oxidation state changes. In this paper, we addressed the Cu2O stability depositing films of 170 nm by reactive radio frequency magnetron sputtering and subsequently ageing them in conditions similar to the typical accelerated life test for the solar module, in a period of time from one to five weeks. The stability of the optical, electrical, and structural properties of the Cu2O thin films was investigated using UV-VIS-near infrared transmittance, 4-probes electrical resistance characterization, high precision profilometry, X-ray photoelectron spectroscopy, and grazing incidence X-ray diffraction. Finally, we demonstrated that the aging tests affected only the surface of the films, while the bulk remained unaltered, making Cu2O a promising candidate for production of stable devices, including solar cells.

Electronic Structure and Ultrafast Electron Dynamics in CuO Photocatalysts Probed by Surface Sensitive Femtosecond X-ray Absorption Near-Edge Structure Spectroscopy

“…We were unable to obtain a pure Cu 2 O sample showing only Cu 1+ due to surface oxidation of Cu 2 O in ambient conditions. 37 However, because the N 2 -annealed sample contains 75% Cu 1+ , it is safe to assume that this represents primarily Cu 2 O. UV−visible spectra obtained for the two samples are consistent with band gap values of Cu 2 O and CuO (Figure S3), further supporting that samples in Figure 1A,B are primarily Cu 2 O and CuO respectively.…”

“…The 2p 3/2 peaks of Cu 2+ and Cu + appear at 932.3 and 933.8 eV, while the 2p 1/2 peaks appear at 952.1 and 953.4 eV respectively. , The integrated XPS spectra were used to calculate the surface oxidation state of the two samples, where the Cu 2+ :Cu 1+ ratio was 0.25:0.75 for the Cu 2 O sample (Figure A) and 0.94:0.06 for the CuO sample (Figure B). We were unable to obtain a pure Cu 2 O sample showing only Cu 1+ due to surface oxidation of Cu 2 O in ambient conditions . However, because the N 2 -annealed sample contains 75% Cu 1+ , it is safe to assume that this represents primarily Cu 2 O. UV–visible spectra obtained for the two samples are consistent with band gap values of Cu 2 O and CuO (Figure S3), further supporting that samples in Figure A,B are primarily Cu 2 O and CuO respectively.…”

Resilience of Cuprous Oxide under Oxidizing Thermal Treatments via Magnesium Doping

“…The conversion of Cu 2 O into CuO is attributed to the diffusion of copper to the surface, which consequently generates copper vacancies in the bulk material, where V Cu split sites are suggested as nucleation centers for CuO . Additionally, direct oxidation of Cu + to Cu 2+ at the surface of the films can promote the formation of CuO, when exposed to moisture and under solar limitation . Recent studies reported the generalization of the presence of CuO at the grain boundaries of Cu 2 O, when deposited by different techniques, leading to a reduction of the electrical performances of cuprous oxide for solar cell applications. − In a study of all-oxide solar cells, both types of copper-based oxides were compared as a photovoltaic p-type absorbing layer, combined with ZnO as an n-type counterpart .…”

Light, Copper, Action: Visible-Light Illumination Enhances Bactericidal Activity of Copper Particles

“…It should be noted that, when oxidized, CuO (Cu 2+ ) exists in a bivalent state with the d 9 character, while in Cu 2 O (Cu + ), the 3d subshell is complete. Nevertheless, although Cu 2 O has completely filled the 3d orbitals, it is less stable than CuO, since stability also depends on the environment in which the material is inserted or where it will be applied. ,− XPS deconvolutions of all Cu 2p bands as well as the C 1s and the O 1s ones are presented in Figures S4 and S5, respectively. Table S1 presents all of the Cu 2p 3/2 , O 1s, and C 1s parameters obtained through XPS profile fitting.…”