Journal
SOLAR ENERGY MATERIALS AND SOLAR CELLS
Volume 209, Issue -, Pages -Publisher
ELSEVIER
DOI: 10.1016/j.solmat.2020.110418
Keywords
Cuprous oxide solar cells; Atmospheric pressure spatial atomic layer deposition; chemical vapour deposition; Interface and bulk defects; Impedance spectroscopy; Quantum efficiency
Funding
- Research Council of Norway through the RENERGI program [ES483391, 1]
- Cambridge Overseas and Commonwealth Trust
- Rutherford Foundation of New Zealand
- ERC Advanced Investigator Grant, Novox [ERC-2009-adG247276]
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Heterojunction Cu2O solar cells are an important class of Earth-abundant photovoltaics that can be synthesized by a variety of techniques, including electrochemical deposition (ECD) and thermal oxidation (TO). The latter gives the most efficient solar cells of up to 8.1% reported in the literature, but is limited by low external quantum efficiencies (EQE) in the long wavelength range (490-600 nm). By contrast, ECD Cu2O gives higher short wavelength EQEs of up to 90%. We elucidate the cause of this difference by characterizing and comparing ECD and TO films using impedance spectroscopy and fitting with a lumped circuit model to determine the trap density, followed by simulations. The data indicates that TO Cu2O has a higher density of interface defects, located approximately 0.5 eV above the valence band maximum (N-V), and lower bulk defect density thus explaining the lower short wavelength EQEs and higher long wavelength EQEs. This work shows that a route to further efficiency increases of TO Cu2O is to reduce the density of interface defect states.
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