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Substrates with extremely low roughness to allow the growth of good-quality silicon material but that nevertheless present high light trapping properties are presented. In a first application, silver reflectors are used in single and tandem-junction amorphous silicon (a-Si:H) solar cells. High initial (stable) efficiencies of 10.4 % (8.1 %) for single-junction a-Si:H cells on glass and 11.1 % (9.2 %) for tandem-junction a-Si:H/a-Si:H cells on plastic are obtained. A second application better suited to multi-junction solar cells based on microcrystalline silicon (μc-Si:H) solar cells is presented: the substrate consists of rough zinc oxide (ZnO) grown on a flat silver reflector which is covered with a-Si:H; polishing of this structure yields an a-Si:H/ZnO interface that provides high light scattering even though the cell is deposited on a flat interface. We present results of ~ 4-μm-thick μc-Si:H solar cells prepared on such substrates with high open-circuit voltages of 520 mV. A large relative efficiency gain of 20% is observed compared to a co-deposited cell grown directly on an optimized textured substrate.
Christophe Ballif, Quentin Thomas Jeangros, Antoine Descoeudres, Andrea Ingenito, Arnaud Walter, Sylvain Nicolay, Soo-Jin Moon, Philippe Wyss
Kumar Varoon Agrawal, Jian Hao, Shuqing Song, Luis Francisco Villalobos Vazquez de la Parra, Shaoxian Li, Deepu Joseph Babu, Heng-Yu Chi, Qi Liu, Yu Han