Degradation of ZnO-Based Buffer Layers for Thin Film CdSeTe/CdTe Solar Cells |
Luksa Kujovic, Ali Abbas, Luke O. Jones, Mustafa Togay, Kieran M. Curson, Nicholas Hunwick, Luis C. Infante-Ortega, Adam M. Law, Jake W. Bowers, John M. Walls Loughborough University, Loughborough, --, United Kingdom |
In this study, we compare the environmental stability of ZnO-based buffer layers for thin film CdSeTe/CdTe solar cells. The buffer layers were deposited on glass substrates using radio frequency sputtering and include zinc oxide (ZnO), magnesium-alloyed ZnO (MZO) and gallium-alloyed MZO. Accelerated lifetime tests (ALTs) were performed by exposing the samples to damp heat and ultraviolet radiation, complying with the conditions required for IEC standard 61215. The optical, electrical, chemical, and structural properties have been studied before and after ALTs. The optical degradation of the samples was evaluated by measuring the transmittance and reflectance spectra. The transmittance data was used to obtain Tauc plots which allowed the bandgaps to be compared. It was found that the electrical properties could not be measured due to the high resistivity of all the materials. The chemical composition of the buffer layers was analyzed using X-ray photoelectron spectroscopy. Scanning electron microscopy was used to observe the surface structure degradation. The results show that ZnO is the most environmentally stable buffer layer. |