| AVS 56th International Symposium & Exhibition | |
| Thin Film | Thursday Sessions |
| Session TF-ThA |
| Session: | Next Generation Processing |
| Presenter: | R.G. Dhere, National Renewable Energy Laboratory |
| Authors: | R.G. Dhere, National Renewable Energy Laboratory J.N. Duenow, National Renewable Energy Laboratory S.E. Asher, National Renewable Energy Laboratory Y. Yan, National Renewable Energy Laboratory M. Young, National Renewable Energy Laboratory T.A. Gessert, National Renewable Energy Laboratory |
| Correspondent: | Click to Email |
The development of CdTe solar cells over the last 35 years has been advanced by introducing various modifications in the fabrication process such as post-deposition CdCl2 heat treatment and CdS deposited by chemical-bath deposition (CBD). The presence of oxygen during various stages of CdTe/CdS device fabrication is also known to benefit device performance. The first devices reported by Kodak to have efficiencies greater than 10% were fabricated by close-spaced sublimation (CSS) in oxygen ambient. CdCl2 heat treatment, crucial for achieving high efficiency, is usually carried out in ambient containing O2. In previous studies on devices fabricated using CBD CdS, CSS, and sputtering, the interdiffusion at the CdS/CdTe interface was correlated to the presence of O2 in CBD CdS. We have fabricated devices with sputtered CdS films that have efficiencies near 14%, comparable to our baseline devices using CBD CdS. In this paper, we present our recent work on CdTe devices using CdS prepared by sputtering and CBD. For sputtered CdS films, we varied O2 content in the sputtering ambient from 0% to 3%. CdTe films were deposited by CSS in oxygen ambient and conventional physical vapor deposition in high vacuum. We will present detailed characterization of the CdS/CdTe interdiffusion at the interface. Specifically, we used secondary-ion mass spectrometry for samples fabricated under different conditions to investigate the dependence of interdiffusion characteristics on oxygen ambient during fabrication. We will also present the results of our transmission electron microscopy analysis on the structural properties of the CdS/CdTe interface and its correlation to the microstructure of CdS deposited by both techniques as well as oxygen in the fabrication process. We will fabricate devices using the samples from these studies and characterize the devices using standard current-voltage analysis. We will then analyze the results to correlate the device properties to the interface properties.