Investigation of alternative window materials for GaAs solar cells |
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Authors: | DeSalvo GC Barnett AM |
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Affiliation: | Dept. of Electr. Eng., Delaware Univ., Newark, DE ; |
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Abstract: | The optimum window material for surface passivation of GaAs solar cells is investigated using theoretical analysis of optical losses due to window bandgap energy and thickness. A simplified expression is developed to calculate the effective surface recombination velocity in terms of lattice mismatch between the window layer and GaAs, which suggests using a window material with and indirect bandgap energy greater than 2.0 eV, a thickness of less than 0.05 μm, and a lattice mismatch of less than 0.05%. Experimental GaAs solar cells were fabricated and quantum efficiency measurements were made using no window (bare GaAs), Al0.7Ga0.3As, Na2S, and ZnSe/Na2S windows. The Al0.7Ga0.3As and Na2S windows are shown to passivate the GaAs surface and reduce the surface recombination velocity to less than 105 cm/s, while the ZnSe encapsulating layer was used to permanently maintain the temporary surface passivation effects from Na2S |
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