Through-the-glass spectroscopic ellipsometry for analysis of the optical structure of CdTe thin-film solar cells in the superstrate configuration

• Published in: Progress in photovoltaics Vol. 24; no. 8
• Main Authors: Koirala, Prakash, Li, Jian, Tan, Xinxuan, Yoon, Heayoung, Marsillac, Sylvain, Rockett, Angus A, Podraza, Nikolas J, Collins, Robert W
• Format: Journal Article
• Language: English
• Published: 01-01-2016
• ISSN: 1062-7995; 1099-159X
• DOI: 10.1002/pip.2759

The polycrystalline CdS/CdTe thin-film solar cell in the superstrate configuration has been studied by spectroscopic ellipsometry (SE) using glass side illumination whereby the reflection from the glass/film-stack interface is collected whereas that from the ambient/glass interface is rejected. The SE data analysis applies dielectric functions ( ε ) for solar cell component materials obtained by variable-angle and in-situ SE. In the SE analysis of the complete cell, a step-wise procedure ranks the free parameters, including thicknesses and those defining the spectra in ε , according to their ability to reduce the root-mean-square deviation between simulated and measured SE spectra, and the best-fit results compare well with electron microscopy. Combining all SE results, the solar cell quantum efficiency (QE) can be simulated without free parameters, and comparisons with QE measurements enable identification of losses. The capabilities have wide applications in photovoltaic module mapping and in-line monitoring.The polycrystalline CdS/CdTe thin-film solar cell in the superstrate configuration has been studied by spectroscopic ellipsometry (SE) using glass side illumination whereby the reflection from the glass/film-stack interface is collected whereas that from the ambient/glass interface is rejected. The SE data analysis applies dielectric functions ( ε ) for solar cell component materials obtained by variable-angle and in-situ SE. In the SE analysis of the complete cell, a step-wise procedure ranks the free parameters, including thicknesses and those defining the spectra in ε , according to their ability to reduce the root-mean-square deviation between simulated and measured SE spectra, and the best-fit results compare well with electron microscopy. Combining all SE results, the solar cell quantum efficiency (QE) can be simulated without free parameters, and comparisons with QE measurements enable identification of losses. The capabilities have wide applications in photovoltaic module mapping and in-line monitoring.