Next-Generation 35-40% Efficient Multijunction Solar Cell: Development of High Efficiency (>35%) and Radiation Resistant 4-Junction Solar Cells on InP

"Brimrose Corporation has identified 0.75, 1.0, 1.5 and 1.91 eV band gap III-V semiconductor materials, lattice matched to InP for producing high efficiency 4- junction solar cells for space application. Phase I objective are follows: (1) Optimize theepitaxial growth of 0.75 and 1.0 eV materials and tunnel junction inter connecting these two band gap solar cells and fabricate a high efficiency single junction solar cell and characterize it to prove the concept and (2) Optimize through modeling andepitaxial growth results the 4-junction solar cell device structure. Phase II objectives are : (1) Optimize the growth conditions for producing the optimized 4-junction solar cell structure and subsequently fabricate and test the 4-junction device. (2)optimize the conditions for large area processing (3"diameter or more) and (3) Design a inter connected dual chamber MOCVD multi wafer production reactor for producing these 4-junction solar cell structure in a continuous manner without the problem ofmemory effects. Samples of single junction cell and details of optimized 4-junction solar cell structure through modeling will be provided to Air Force at the end of Phase I program. The success of the research will be the availability of very highefficiency 4-junction solar cell for space application. The major spin off is the use of this solar cell system for production of high efficiency concentrator terrestrial solar energy conversion system."