High Efficiency GaAs/Ge Monolithic Tandem Solar Cells

S. P. Tobin, S. M. Vernon, C. Bajgar, V. E. Haven, L. M. Geoffroy, M. M. Sanfacon, D. R. Lillington, R. E. Hart, K. A. Emery, R. J. Matson

Research output: Contribution to conferencePaperpeer-review

30 Scopus Citations


Two-terminal monolithic tandem cells consisting of a GaAs solar cell grown epitaxially on a Ge solar cell substrate are very attractive for space applications. Tandem cells of GaAs grown by metal-organic chemical vapor deposition on thin Ge were investigated to address both higher efficiency and reduced weight. Two materials growth issues associated with this heteroepitaxial system, autodoping of the GaAs layers by Ge and diffusion of Ga and As into the Ge substrate, were addressed. The latter appears to result in information of an unintentional p-n junction in the Ge. Early simulator measurements gave efficiencies as high as 21.7% for 4 cm2 GaAs/Ge cells, but recent high-altitude testing has given efficiencies of 18%. Sources of errors in simulator measurements of two-terminal tandem cells are discussed. A limiting efficiency of about 36% for the tandem cell at AMO was calculated. Ways to improve the performance of present cells, primarily by increasing the Isc and Voc of the Ge cell, are proposed.

Original languageAmerican English
Number of pages6
StatePublished - 1988
Externally publishedYes
EventTwentieth IEEE Photovoltaic Specialists Conference - 1988 - Las Vegas, NV, USA
Duration: 26 Sep 198830 Sep 1988


ConferenceTwentieth IEEE Photovoltaic Specialists Conference - 1988
CityLas Vegas, NV, USA

NREL Publication Number

  • ACNR/CP-213-11096


Dive into the research topics of 'High Efficiency GaAs/Ge Monolithic Tandem Solar Cells'. Together they form a unique fingerprint.

Cite this