Cigs Thin Film Solar Cells Fabricated on The Various Substrates

New Possibility for Research and Business Integration

Abstract

Solar cells which based on silicon or binary III–V semiconductor compounds and their solid solutions successfully fulfilled their role as the first energy sources in outer space in the 1950s–1990s. Concentrator cascade of solar cells formed as heterostructures, based on InGaAsP solid solutions grown on germanium substrates, ensured progress in improving their main parameters, such as power density, the ratio of power/weight, and the solar cells operating time, however, the cost of photoconverters drastically increased as a result of these improvements. Evidently, the observed steady increase in the number of launched artificial satellites and a tightening of requirements for the size, weight, and cost of space technology have stimulated a continuous increase in demand for high efficiency solar cells, which are fabricated by low cost technologies and, at the same time, feature low weight parameters.The results of measuring the first spectra of relative quantum efficiency for photoconversion in thin film ZnO/CdS/Cu(In, Ga)Se2/Mo solar cells (CIGS solar cells) fabricated on rigid (glass) and flexible (polyimide) substrates are reported. The character of interband transitions has been studied and the values of the band gap for direct and indirect transitions in thin Cu(In, Ga)Se2 films are determined. It is found that a shift of the maximal photosensitivity for the obtained solar cells to shorter wavelengths is observed as rigid substrates are replaced by flexible ones. It is concluded that thin film Cu(In, Ga)Se2 structures can be used as broad band photoconverters of solar radiation with low costs. This study was supported by the contract “Research and Development of Deposition System for CIGS Solar Cell” signed by the Ioffe Physical Technical Institute (Russian Academy of Sciences).