Density functional theory study explaining the underperformance of copper oxides as photovoltaic absorbers

Abstract

Most photovoltaic absorbers are identified using the standard Shockley-Queisser selection principle which relies on optimal band-gap values. However, this criterion has been shown to be insufficient, as many materials with appropriate values still perform badly. Here, we have employed calculations based on the density functional theory to assess three copper oxides as potential photovoltaic materials: Cu 2 O, Cu 4 O 3 , and CuO. Despite their promising theoretical solar power conversion efficiency of over 20%, experimental values are found to be far lower. Theoretical evaluation of the electronic and optical properties reveals that certain transitions within the band structures are dipole forbidden, whereas the fundamental band gaps of Cu 4 O 3 and CuO are of indirect nature. These findings correlate to the weak and shifted absorption properties found experimentally, which underpin the inefficient light capture by copper oxides. Based on these results and an applied extended selection metric, we can explain why copper oxides are unable to reach the efficiencies previously proposed theoretically and why we need to revise their maximum conversion values.

Nitrogen Doping Effect in Cu4O3 Thin Films Fabricated by Radio Frequency Magnetron Sputtering

“…To analyze the absorption spectra, the fitting was performed using the aforementioned expression. The fitting using a direct forbidden transition gap model gives good match to the experimental data as shown by dashed lines in Figure . For the undoped and N‐doped Cu 4 O 3 films deposited at N 2 flow rate from 0 to 4.30 sccm, an optical band gap was obtained in between l.34 and 1.44 eV.…”

Acceptor‐Doping Accelerated Charge Separation in Cu2O Photocathode for Photoelectrochemical Water Splitting: Theoretical and Experimental Studies

“…Ni 2+ has a similar ionic radius (0.72 Å) with Cu + (0.77 Å) and is expected to have an ignorable effect on the structure of Cu 2 O lattice. Previous theoretical results suggest that Ni dopants induce a small lattice distortion (0.078 %) and increase the solar conversion efficiency of Cu 2 O . Moreover, density‐functional theory (DFT) results suggest that the Ni dopants would alter the p‐type feature of bulk Cu 2 O .…”

Functional Oxides for Photoneuromorphic Engineering: Toward a Solar Brain

“…), there are many oxides potentially suitable as light harvesters. However, as silicon and other III-V semiconductors (and, more recently, chalcogenides and halides) have historically received much more attention, only a bunch of metal oxides have been seriously investigated as the photon harvester media [221] . the CuO x bandgap can be tuned to cover the entire range in between 1.4-2.2 eV [222] .…”