CuInGaAlSe2 Solar Absorbers On Flexible High-Temperature Substrates

ITN Energy Systems (ITN) proposes to take the next step in spacecraft solar array development, building upon previous development and new findings to make the definitive light-absorber layer for high-power, lightweight and flexible thin-film photovoltaics (TFPV). ITN's innovative approach is to alloy CuInSe2 (CIS) with both aluminum and gallium bandgap widening elements in the chalcopyrite matrix to form CuInGaAlSe2 (CIGAS) for simultaneous optimization of the bandgap and material properties. Both Ga and Al will be used to take advantage of the alloy enhancing properties that each offers when used in moderation, while avoiding the detrimental issues when using too much of any one element to achieve the optimum bandgap of about 1.45 eV for a single-junction in the space solar spectrum. Furthermore, a recently available novel lightweight, flexible and transparent substrate will be used that was specifically designed to enable high-temperature CIGAS depositions as needed for the highest efficiency TFPV. TFPV specific power of over 1500 W/kg at the blanket/module level would be achievable The novel transparent substrates would also enable additional power from bifacial visible light collection and lower temperature operation, from improved infra-red (IR) transmission, in addition to enabling TFPV fabrication by low-cost roll-to-roll processing.