| Summary: | 碩士 === 國立中興大學 === 精密工程學系所 === 96 === The major topic of this thesis is the investigation of GaInP/GaAs tandem solar cells. To improve the efficiency of solar cells, this research investigates the critical techniques of multi junction tandem solar cell, based on the epitaxy techniques and post-growth fabrication processes. The basic epitaxy parameters which include the material composition and dopant concentration versus precursor flow rate of AlInP, GaInP, AlXGa1-XInP and GaAs. In post-growth fabrication processes, this thesis also discusses about the process of top and bottom metal electrodes evaporation, the conditions of alloy process, the selectivity-etching of contact layer, and the parameters of anti-reflection coating evaporation.
In accordance with GaAs solar cell structure, the influence of emitter and window layers thickness is discussed. Based on the experimental results, the emitter layer is 200 nm thick, and the solar cell would result in higher ISC. On the side of window layer, GaInP is selected as this layer material, the optimum efficiency can be obtained by tuning this layer thickness up to 50 nm.
In the research of GaInP/GaAs tandem solar cell, the GaInP top cell efficiency is 6.34%, and the GaAs bottom cell efficiency is 12.67%. For the GaAs:C/GaAs:Si tunnel diode selected, both sides are doped heavily, the ratio of peak current and valley current, IP:IV, is 10:1. Finally, the GaInP/GaAs tandem solar cell efficiency is 4.22 %. The reason that the efficiency decreased is the short current Isc limited by current-match and the degradation of tunnel junction.
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