Current Trends Although the production run involved ‘frozen' procedures, tests showed that it was possible to achieve efficiencies comparable to those reported above for cells grown in the large-scale production reactors and processed with standard production methods. Figure 2 shows the I-V curve for a 2 X 2 cm2 GaAs/GaAs cell with efficiency around 21.5% (AMO). The results shown in Tables I and II and in Fig. 2 suggest that with some further fine-tuning, the GaAs cells on passive-Ge substrates can reach even higher efficiencies than achieved to date. For production runs, either of GaAs/GaAs or GaAs/Ge cells, increased median efficiency values are projected, first to around 18.5%, with chance of further increase in future runs. When these higher efficiencies are obtained for larger area, thinner cells with the operating advantages of GaAs/GaAs cells, it is apparent that GaAs/Ge can offer advantages to designers of advanced arrays. Either more power can be obtained from the same area or for the same power, the arrays can have 20-30% lower area. Although Ge and GaAs are both more than twice as dense as Si, at the array level, 3-4 mil thick GaAs/Ge cells can be shown to have advantages in watts per kilogram and watts per square metre. Even though the cost of GaAs cells is higher than the cost of Si cells, the cost impact is reduced when overall system costs are assessed. For these reasons, GaAs/Ge cells are now competitive in many applications where
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