Short-circuit current improvement in CdTe solar cells by combining a ZnO buffer layer and a solution back contact |
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Authors: | Eun Seok Cha Young Min Ko Seon Cheol Kim Byung Tae Ahn |
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Affiliation: | Dept. of Materials Science and Engineering, Korea Advanced Institute of Science and Technology, 291 Daehak-ro, Yuseong-gu, Daejeon, 34141, Republic of Korea |
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Abstract: | Conventional CdTe solar cells have a CdS window layer, in which an absorption loss of photons with more than 2.4 eV occurs through the CdS layer. A thinner CdS layer was applied to enhance light transmission and a ZnO buffer layer with a band gap of 3.3 eV was introduced to suppress shunting through the thinner CdS window layer. A 100-nm thick ZnO layer sputter-deposited at 300 °C had uniform coverage on a transparent conductive oxide (TCO) after a subsequent high-temperature process. The ZnO layer was effective in preventing shunting through the CdS window layer so that the open-circuit voltage and fill factor of the CdTe solar cells were recovered and the short-circuit current was enhanced over that of the conventional CdTe solar cell. In the ZnO/CdS/CdTe configuration, the short-circuit current was further improved throughout the visible wavelength region by replacing the Cu-metal contact with a Cu solution contact. As a result the short-circuit current from 21.7 to 26.1 mA/cm2 and the conversion efficiency of the CdTe solar cell increased from 12 to 15% without antireflective coating. Our result indicates that the Cu solution back contact is a critical factor for achieving a higher cell efficiency in addition to ZnO buffer layer. |
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Keywords: | CdTe solar cells ZnO buffer layer Cu solution contact Short circuit current Quantum efficiency |
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