The typical performances of GaAs cells mounted on polyimide panel are as follows. Cell efficiency Panel efficiency Weight Area Cost Radiation degradation (Conditions : After 10 years in a 840 km 80 deg. inclination orbit, CMZ cover glass, unframed panel.) InP (Indium Phosphide) This material has the advantage that its radiation degradation is very low. Also, the theoretical efficiencies are high, with laboratory cells demonstrating about 19% (AMO : Air Mass 0) efficiency at this time. Material costs are very high and resources of Indium are rare at this time.[Ralph, 1989] The typical performances of InP cells mounted on a polyimide panel are as follows: Cell efficiency Panel efficiency Weight Area Radiation degradation (Conditions : After 10 years in a 840 km 80 deg. inclination orbit, CMZ cover glass, unframed panel.) CulnSe2 (Copper Indium Diselenide) This material can be a thin-film cell. The advantages of thin-film cells are: high radiation tolerance, high specific power, large area solar cells with integral series interconnections, flexible blankets, large body of array manufacturing experience and low cost. The disadvantages of thin- film cells are: lower efficiency, lack of spacecraft experience and no light weight substrates have been produced for space use. As a feature of CuInSej, the bandgap is 1.0 eV, which is on the low side of the AMO efficiency maximum, but nearly ideal for the bottom cell of a multi-bandgap cascade structure. An efficiency of 10.4%(AM0) has been achieved by Arco Solar (now Siemens Solar). An efficiency of 12% has been predicted in the near term. The absorption constant of CuInSej is extremely high, allowing the possibility of cells as thin as one micron. Existing cells consist of a layer of the active CuInSei, typically about 3 microns in thickness. So, the current specific power is relatively high, 7.0 kW/kg (does not include coverglass). [Landis, 1989] CdTe (Cadmium Telluride) CdTe is also being extensively studied for thin-film cells. The bandgap of CdTe is 1.5 eV and is very well matched to the solar spectrum.
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