| The high efficiency and triple-junction GaAs solar cell is a III-V group compound semiconductor photoelectric conversion device. Compared with silicon solar cell which is widely used now, GaAs solar cell has higher photoelectric conversion efficiency, stronger radiation resistance ability and better high temperature tolerance performance. It has become the most competitive new generation solar cell across the world, and it's gradually extending its application range in the field of spaceflight. GaAs solar cell is the general space main power supply with high performance and long life in dire need of spaceflight aircraft in China.The paper firstly Integrated with theory basis, AMPS software and relevant test parameters, the model of gradual changing band gap structure in III/V group AlxGa1-xAs solar cell has the analogical analysis to its parameters as electron life, cavity life and total amount of photo generated carrier, etc. It concludes that the gradual changing structure of band gap has various modulation effects to the practical generation and collection of carrier. It also confirms the structure area and scope of gradual changing band gap in solar cell as well as corresponding spectral area and light flux which are the leading factors to the solar cell efficiency. achieving GaAs solar cell of gradual change in band gap with 25.2% efficiency ,According to the test of second ion mass spectrum (SIMS), it proves the cell we developed has the structure of gradual changing band gap, which provides a brand new idea of cell structure for the further study in high-efficient cell. secondly Improved the technology oft GaInP2/GaAs/Ge triple junction solar cell, including the following(1) The selection, structure design and successful realization of the window-layer material of Ge bottom cell can slow down interface recombination speed and improve spectral effect of Ge bottom cell.(2)Medium cell adopts InxGa1-xAs material which matches Ge crystal lattice better. It can significantly decrease recombination and extend life of minority carrier as well as raise the availability ratio of medium wave in sunbeam in order to get higher Jsc.(3) The design and application of n+-n-/p—p+ structure with field-aided collection effect is able to efficiently solve the problems that the minority carrier life of GaInP2 material is short which causes the low light current of top cell. Meanwhile, appropriately increasing the thickness of top cell base and improving the current matching between sub-cells will significantly raise the short circuit current density or Jsc of GaInP2 top cell. ( 4 ) Tunneling junction uses wide forbidden band materials AlGaAs/GaAs or AlGaAs/ GaInP2 and at the same time reduces its thickness as well as raise its concentration, which can get higher tunneling current.The designs and methods mentioned above which are put into operation in GaInP2/(In)GaAs/Ge triple junction superposition solar cell can significantly raise short circuit current density, which can make Jsc up to 16.59mA/cm2, as well as photoelectric conversion efficiency of the cell, which can be up to 26.4%(AM0, 25C).Finally ,Contriving radiation resistance and reinforce of GaInP2/GaAs/Ge triple junction solar cell, this project standardizes demand of 5 to 8 low-tunnel life and carry electronic radiation of 1MeV, 1×10 15 e/cm2 under room temperature to the GaInP2/GaAs/Ge triple junction solar cell and its top sub-cell and medium sub-cell, then anneals for 10 hours with 80℃In order to have better radiation resistance performance, top cell should be improved as following: (1) use n+-n-/p--p+ structure, which has field-aided collection effect, to replace the normal n/p structure, in order to get higher light current as well as reduce the damage level of cell radiation; (2) base region with doping level of～1016cm-3 and thickness of 0.55 to 0.8um can have higher open circuit voltage, more suitable light current and lower radiation efficiency attenuation; (3) higher doping and thinner emission area should choose doping level of 1018～1019 cm-3. To the base region of medium cell, its thickness should be 3um when efficiency radiation attenuation can be less than 22%. Applied the improvements mentioned above to the GaInP2/GaAs/Ge triple junction solar cell, its radiation attenuation is 21.42%. |
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