Development and Characterization of III-V/Si Multijunction Photovoltaics for Space Application
Jacob T. Boyer1, Daniel L. Lepkowski2, Daniel J. Chmielewski2, Daniel Derkacs3, Christopher Kerestes3, Alex Stavrides3, Steven Whipple3, Steven A. Ringel1,2, Tyler J. Grassman1,2
1Dept. of Materials Science and Engineering, The Ohio State University, Columbus, OH, United States
/2Dept. of Electrical & Computer Engineering, The Ohio State University, Columbus, OH, United States
/3SolAero Technologies, Corp, Albuquerque, NM, United States

As small satellite and related technologies continue to rise, power systems must provide adequate power while maintaining low cost and form factor to make missions viable. III-V/Si multijunction photovoltaics have great potential toward this end, leveraging low cost, processible, and lightweight Si substrates with epitaxially integrated III-V top cell(s), breaking the Si efficiency ceiling. III-V/Si dual junction (2J) tandem photovoltaics with potential for space deployment have been under development. Individually developed components of the 2J tandem, which include, a Si subcell, GaP/Si nucleation layer, metamorphic GaAsyP1-y buffer, metamorphic tunnel junction, and a GaAs0.7P0.3 top cell, have been combined into preliminary 2J devices. Following MOCVD growth at OSU, Fabrication was performed at SolAero, demonstrating compability with industrial processes and resulting in several 2 cm x 2 cm test devices. These preliminary 2J tandem devices exhibit 16-18% AM0 efficiency and are limited by the bottom cell. Temperature dependent LIV has been conducted and initial space-relevant characterization including thermal cycling and thermal balance measurements are underway. The addition of simple Si subcell architectures, reduced defect density GaP/Si nucleation layers, and enforcing current matching offer a promising pathway to tandem AM0 efficiencies of >25%.