High efficiency ultra lightweight a-Si:H/a-SiGe:H/a-SiGe:H triple-junction solar cells on polymer substrate using roll-to-roll technology

A roll-to-roll manufacturing technology has been developed for fabricating lightweight, high efficiency and flexible triple-junction thin film a-Si:H/a-SiGe:H/a-SiGe:H solar cells on polymer substrate for the emerging space and near-space stratospheric markets. The highest initial (before light soak), 25°C, aperture-area (721.8 cm²), AM0 efficiency attained was 9.7%. The highest initial specific power was ∼1200 W/kg with a proprietary top coating ∼0.25 mil thick. In order to develop the next generation space photovoltaic technology, effort has been made on developing nc-Si:H material. We have fabricated large area a-Si:H/nc-Si:H double-junction solar cells on 5 mil thick steel and 1 mil thick polymer substrates and demonstrated an initial AM0 active-area efficiency of around 10% on a 462 cm² device.