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Bifacial Amorphous Si Quintuple-Junction Solar Cells for IoT Devices with High Open-Circuit Voltage of 3.5V under Low Illuminance
M. Konagai, R. Sasaki
Solar Cell, Amorphous Silicon, Quintuple-Junction, Low Illuminance
Silicon Materials and Cells
Subtopic: Thin Film and Foil-Based Si Solar Cells
Event: 36th European Photovoltaic Solar Energy Conference and Exhibition
Session: 2AO.6.4
140 - 146
ISBN: 3-936338-60-4
Paper DOI: 10.4229/EUPVSEC20192019-2AO.6.4
0,00 EUR
Document(s): paper


Hydrogenated amorphous Si(a-Si:H) Quintuple-junction solar cells which consist of a-SiOx:H/aSiOx:H/a-Si:H/a-SiOx:H/a-SiOx:H were fabricated by plasma CVD method. The total thickness was 0.6-0.8 m. Irradiation intensity (Pin) dependence of the open circuit voltage (Voc) of quintuple-junction solar cells was measured. The decreasing amount Voc (1/10) of the open-circuit voltage when the irradiation intensity became 1/10 was 62mV/cell. Voc drops rapidly from around the irradiation intensity of 1mW/cm2 (approximately 1,000 lux). This large Voc reduction is due to leakage current. Then, we discussed the origin of the leakage current, and finally by improving the leakage current, a very high open-circuit voltage Voc of 3.5 V was demonstrated under LED light illumination. Furthermore, we theoretically analyzed Voc as a function of the irradiation intensity, including effects of the leakage current and the film quality of i-a-Si(O):H. It was found from the simulation results that it is necessary to increase the shunt resistance Rsh and to lower the defect density of i-a-Si(O):H in order to obtain a sufficient Voc-Pin characteristics for IoT devices application under low illuminance.