Development of amorphous silicon-based thin-film solar cells with low-temperature coefficient

Abstract

In this work, we investigated the temperature dependence of wide bandgap hydrogenated amorphous silicon (a-Si:H)-based, hydrogenated amorphous silicon oxide (a-SiO:H)-based single-junction and hydrogenated protocrystalline silicon/hydrogenated microcrystalline silicon (pc-Si:H/μc-Si:H) double-junction solar cells in order to develop solar cells which are suitable for use in high temperature region. Photo J-V characteristics were measured under AM 1.5 illumination at ambient temperature in the range of 25-75 ^oC. We found that, the values of temperature coefficient for conversion efficiency (TC for η) of both single- and double-junction solar cells were inversely proportional to the initial open-circuit voltage (V_oc). In case of p-i-n single-junction solar cells, the typical pc-Si:H and pc-SiO:H solar cells showed the lowest TC for η of -0.21 and -0.14%/^oC, respectively. The smallest TC for η of pc-SiO:H solar cell was attributed to the positive increase in TC for fill factor (FF). The TC for η of typical pc-Si:H/μc-Si:H double-junction solar cells was around -0.35%/^oC with initial η around 10-12%. Since high V_oc pc-Si:H/μc-Si:H double-junction solar cells exhibit low temperature dependence and highly stable η against light soaking, they are promising for use in high temperature regions. In addition, we conclude that solar cells which are suitable for use in high temperature region must be considered both high η with low temperature dependence.