Pacific Rim Symposium on Surfaces, Coatings and Interfaces (PacSurf 2014)
    Energy Harvesting & Storage Wednesday Sessions
       Session EH-WeP

Paper EH-WeP15
Positive Temperature Coefficient of CdS/Cu(In,Ga)(S,Se)2 Solar Cell

Wednesday, December 10, 2014, 4:00 pm, Room Mauka

Session: Energy Harvesting & Storage Poster Session
Presenter: Sangmok Kim, Yeungnam University, Republic of Korea
Authors: S. Kim, Yeungnam University, Republic of Korea
C.-W. Jeon, Yeungnam University, Republic of Korea
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In the recent years, Cu(In, Ga)Se2 (CIGS)-based thin-film solar cells with efficiency of readily over 20% have been reported by several groups, therefore, it is strongly expected to replace the crystalline silicon solar cell rapidly. Unlike crystalline silicon cell of a homo-junction, CIGS thin-film solar cell consists of hetero-junction between absorbing layer and CdS buffer layer. In CBD (Chemical Bath Deposition)-CdS, which is commonly used for a high efficiency CIGS solar cell, the kind and concentration of source materials and bath temperature is known to affect the characteristics of the CIGS/solar cell as well as CdS film properties. In general, the efficiency of solar cell decreases with increasing ambient temperature due to the reduction of band gap energy of absorber layer and higher reverse saturation current at an elevated temperature. In other words, temperature coefficient (TC) of a solar cell is normally negative. [1] While this tendency is observed in the CIGS/CdS solar cells, according to this study, it was confirmed that the behavior of TC depends on the synthesis conditions of the CdS. In this study, we prepared several solar cells of ZnO/CdS/ CIGS/Mo/glass with different CdS deposition conditions by changing [Cd] and [S] in the solution over the range of [Cd]=15~135mM, [S]=12.5~50mM. And the variation of TC’S were monitored by measuring IVT (Current-Voltage-Temperature) in the temperature range of 10~50℃. Some of solar cells with high [Cd] of low [S] were found to have positive TC’s. In these devices, while Voc decreased as expected with increasing temperature, fill factor increased on the contrary. The enhancement of fill factor stemmed from the lower series resistance at higher operating temperature. The thermal characteristics of the solar cells depending on the [S]/[Cd] composition ratio in the solution will be discussed with the results of IV, CV, QE measurements. Acknowledgement This research was financially supported by the Ministry of Knowledge Economy(MKE), Korea Institute for Advancement of Technology(KIAT) and Dae-Gyeong Leading Industry Offic through the Leading Industry Development for Economic Region. References [1] A.Virtuani, D. Pavanello, and G. Friesen, 25th European Photovoltaic Solar Energy Conference and Exhibition/5th World Conference on Photovoltaic Energy Conversion. 2010, p6-10