The earth-abundant material CuSbS2 (CAS) has shown good optical properties as a photovoltaic sola... more The earth-abundant material CuSbS2 (CAS) has shown good optical properties as a photovoltaic solar absorber material, but has seen relatively poor solar cell performance. To investigate the reason for this anomaly, the core-levels of the constituent elements, surface contaminants, ionization potential, and valence band spectra are studied by x-ray photoemission spectroscopy (XPS). The ionization potential and electron affinity for this material (4.98 eV and 3.43 eV) are lower than for other common absorbers, including CuInxGa(1-x)Se2 (CIGS). Experimentally corroborated density functional theory (DFT) calculations show that the VBM is raised by the lone pair electrons from the antimony cations contributing additional states when compared with indium or gallium cations in CIGS. The resulting conduction band misalignment with CdS is a reason for the poor performance of cells incorporating a CAS/CdS heterojunction, supporting the idea that using a cell design analogous to CIGS is unhelp...
The earth-abundant material CuSbS2 (CAS) has shown good optical properties as a photovoltaic sola... more The earth-abundant material CuSbS2 (CAS) has shown good optical properties as a photovoltaic solar absorber material, but has seen relatively poor solar cell performance. To investigate the reason for this anomaly, the core-levels of the constituent elements, surface contaminants, ionization potential, and valence band spectra are studied by x-ray photoemission spectroscopy (XPS). The ionization potential and electron affinity for this material (4.98 eV and 3.43 eV) are lower than for other common absorbers, including CuInxGa(1-x)Se2 (CIGS). Experimentally corroborated density functional theory (DFT) calculations show that the VBM is raised by the lone pair electrons from the antimony cations contributing additional states when compared with indium or gallium cations in CIGS. The resulting conduction band misalignment with CdS is a reason for the poor performance of cells incorporating a CAS/CdS heterojunction, supporting the idea that using a cell design analogous to CIGS is unhelp...
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Papers by Adam Welch