Title :
High efficiency InGaP/InGaAs tandem solar cells on Ge substrates
Author :
Takamoto, Tatsuya ; Agui, Takaaki ; Ikeda, E. ; Kurita, Hiroshi
Author_Institution :
Japan Energy Corp., Saitama, Japan
Abstract :
Over 30% AM1.5G efficiency was achieved by adding a small quantity of indium into a GaAs bottom cell in the conventional tandem cell on a Ge substrate. Characteristics of InGaAs cells on Ge were investigated by varying In-composition. The maximum efficiency was obtained for the cell with 0.01 In-composition, which was lattice-matched to Ga and produced no misfit-dislocations. Relatively high efficiencies were obtained for the cells with In-compositions less than 0.1, which did not produce cracks but misfit-dislocations. InGaP/InxGa1-xAs tandem cells with In-composition x between 0.01 and 0.07 demonstrated higher efficiency than the conventional InGaP/GaAs cells, that was attributed to an increase in photo-currents both in the top and bottom cells. Remarkably, an In0.49Ga0.51P/In0.01 Ga0.99As tandem cell lattice-matched to Ga showed an improvement in Voc, which was attributed to an elimination of misfit-dislocations in thick GaAs layers. Also, those lnGaP/Inx Ga1-xAs cells with low In-compositions were found to be favorable for improving efficiency of triple junction cells using Ga cells. Over 31% AM1.5G efficiency was demonstrated for the lnGaP/InxGa1-xAs/Ge triple-junction cells with In-composition x of 0.01 and 0.06, at present
Keywords :
elemental semiconductors; gallium arsenide; gallium compounds; germanium; indium compounds; p-n heterojunctions; semiconductor device measurement; semiconductor device testing; solar cells; substrates; In0.49Ga0.51P-In0.01Ga0.99 As; InGaP-InGaAs-Ge; InGaP-InGaAs-Ge tandem solar cells; lattice matching; misfit-dislocations elimination; photovoltaic characteristics; substrate; triple junction cells; Abstracts; Gallium arsenide; Indium gallium arsenide; Lattices; Manufacturing; NASA; Photovoltaic cells; Production; Satellites; Space technology;
Conference_Titel :
Photovoltaic Specialists Conference, 2000. Conference Record of the Twenty-Eighth IEEE
Conference_Location :
Anchorage, AK
Print_ISBN :
0-7803-5772-8
DOI :
10.1109/PVSC.2000.916049