Temperature Dependence of Protocrystalline Silicon/Microcrystalline Silicon Double-Junction Solar Cells

Abstract

We have investigated the temperature dependence of hydrogenated protocrystalline silicon (pc-Si:H)/hydrogenated microcrystalline silicon (µc-Si:H) double-junction solar cells. A boron-doped zinc oxide (ZnO:B) film is employed as an intermediate layer between the pc-Si:H top cell and the µc-Si:H bottom cell. The fabricated solar cells exhibit good stability against light soaking. Photocurrent density–voltage (photo J–V) characteristics are measured under AM 1.5 illumination at ambient temperatures in the range of 25–75 °C. The double-junction solar cells show a temperature coefficient (TC) for conversion efficiency (η) of around -0.30 to -0.45%/°C, which between the TC for η of the pc-Si:H top and µc-Si:H bottom cells. It is found that the values of TC for η are inversely proportional to the initial open-circuit voltage (Voc). In contrast, these values become higher with the increase in the crystalline volume fraction (Xc) of the i-µc-Si:H in the bottom cells. Since the pc-Si:H/µc-Si:H double-junction solar cells exhibit high η, low light-induced degradation, and low temperature dependence, they are good candidates for solar cells that operate in high-temperature or tropical regions.