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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
Author(s) -
Konagai Makoto,
Sasaki Ryo
Publication year - 2020
Publication title -
progress in photovoltaics: research and applications
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.286
H-Index - 131
eISSN - 1099-159X
pISSN - 1062-7995
DOI - 10.1002/pip.3215
Subject(s) - open circuit voltage , irradiation , materials science , optoelectronics , illuminance , amorphous silicon , amorphous solid , leakage (economics) , voltage , short circuit , solar cell , light intensity , analytical chemistry (journal) , optics , electrical engineering , crystalline silicon , chemistry , physics , engineering , organic chemistry , chromatography , nuclear physics , economics , macroeconomics
Hydrogenated amorphous Si(a‐Si:H) quintuple‐junction solar cells, which consist of a‐SiO x :H/a‐SiO x :H/a‐Si:H/a‐SiO x :H/a‐SiO x :H, were fabricated by plasma CVD method. The total thickness was 0.6‐0.8 μm. Irradiation intensity ( Pin ) dependence of the open circuit voltage ( V oc ) of quintuple‐junction solar cells was measured. The decreasing amount ΔV oc (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/cm 2 (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 V oc 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.