Effects of Cu doping on CdTe thin-film solar cells in substrate configuration

Abstract

Substrate-type CdTe thin-film solar cells with a carbon/CdTe/CdS/ZnO:Al/Ag structure were fabricated. For promoting the formation of the CdSxTe1-x mixed crystal layer in the CdS/CdTe interface, the heat treatment (a face-to-face annealing at 600 °C and the second CdCl2 treatment at 415 °C) of the CdS/CdTe:Cu structure was performed after the CdS deposition. Junction photoluminescence and the compositional depth profile revealed that the CdSxTe1-x mixed crystal layer was formed in the CdS/CdTe interface as a result of the heat treatment after the CdS deposition. The cell performance was slightly improved due to the heat treatment after the CdS deposition, but the conversion efficiency remained low (less than 2%), probably due to the decrease in the acceptor concentration in CdTe layer. For improving cell performance, Cu diffusion was performed after the heat treatment of the CdS/CdTe structure (second Cu doping), in addition to the Cu doping before the CdS deposition (first Cu doping). The conversion efficiency increased with increasing Cu concentration in the second Cu doping, and approximately 10% efficiency was achieved.

Epitaxial CdTe Thin Films on Mica by Vapor Transport Deposition for Flexible Solar Cells

“…There is no CdS x Te 1 ‑x layer formed at the interface of the poly-CdS/epi-CdTe heterojunction. The formation of CdS x Te 1– x mixed crystal layer reduced the interface defects at the epi-CdS/epi-CdTe heterojunction . The result is consistent with the C – V profiling and DLCP results that the epi-CdS/epi-CdTe device has lower interface defects.…”

“…The formation of CdS x Te 1−x mixed crystal layer reduced the interface defects at the epi-CdS/epi-CdTe heterojunction. 40 The result is consistent with the C−V profiling and DLCP results that the epi-CdS/epi-CdTe device has lower interface defects. In addition, the formation of CdS x Te 1−x mixed layer can reduce the thickness of the CdS layer, which enables more light going through the CdS layer and incident into the absorb layer.…”

Gamma-ray irradiation effects on CdTe solar cell dosimeter

“…The CdTe solar cells were fabricated by the method reported in previous papers. [25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40] For evaluation of the γ-ray tolerance, γ-ray irradiation was divided into multiple time-frames. γ irradiations were provided at the 60 Co γ-ray irradiation facility at Institute for Integrated Radiation and Nuclear Science, Kyoto University.…”

“…However, it was reported that J SC decreased due to a decrease in the carrier concentration of the p-CdTe layer, because electron-hole pairs had a high probability to recombine before they were collected due to the small electric field near the CdS/CdTe interface. 35,44) Therefore, it is necessary to find a method to increase the sensitivity without changing the area and the layer thickness. In this work, we propose stacking the CdTe solar cells with a parallel connection.…”

CdTe Photovoltaics in Superstrate Geometry–Back-Contact Materials: A Review

“…Also, the double thermal treatment of the CdTe layer initially after deposition of the CdTe layer and then post-CdS deposition treatments result in a better crystal structure. Compared to the superstrate-structured CdTe photovoltaic devices, the number of works in the substrate configuration is less, and HTLs made of ZnTe, Sb 2 Te 3 , MnTe 2 , carbon, etc., were reported. All works confirmed that the diffusion rate of impurities into the CdTe absorber layer would be higher in the substrate configuration because it involves annealing after deposition of the back contact and HTL layer.…”