| dc.description.abstract | In this thesis, the GaInP solar-cells which are the top cell of the GaInP/GaInAs/Ge triple-junction solar-cell have been fabricated with several different epitaxial conditions, in order to improve the characteristics of the GaInP solar-cells under one sun, AM1.5G, condition.
Firstly, the effects of emitter thickness have been studied. By employing a thinner emitter, the cell efficiency can be improved mainly due to the increasing of short-circuit current density.
Secondly, different base doping profiles have been employed. The results indicate a graded base doping can generate a “drift-field” in the base region, which enhances the transports of majority and minority carriers, thus improves the short-circuit current density and conversion efficiency.
Thirdly, following the consequence of the second experiment, the short-circuit current density and conversion efficiency can be further improved by employing a thicker base layer.
Finally, three different materials for back-surface field (BSF) layer, AlGaInP, GaInP, and AlInP have been adopted, respectively. From the experiment results, it seems that the solar-cell performance is directly related to the degree of conduction-band offset at the interface between base and BSF. The solar-cell with an AlInP BSF which has the largest conduction-band offset, demonstrates the highest conversion efficiency, mainly due to the largest short-circuit current density.
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