Research on Stable, High-Efficiency Amorphous Silicon Multijunction Modules, Semiannual Subcontract Report, 1 August 1989 - 31 January 1991

Abstract

This report describes a contract to produce multijunction modules based entirely on amorphous silicon alloys, the modules having an aperture area of at least 900 cm{sup 2} and a stable, reproducible conversion efficiency of at least 6.5% after 600 hours of light exposure (air mass 1.5) at 50{degrees} C. The work focussed on (1) producing opto-electronic-grade amorphous silicon material for band gaps of about 1.7 and 1.9 eV by changing the hydrogen content in the film bonded to the silicon, (2) studying and obtaining data on the light stability of single-junction p-i-n solar cells with gaps of about 1.7 and 1.9 eV, and (3) analyzing losses in a silicon/silicon multijunction cell. We report new results on an indium tin oxide (ITO)/silver back contact and the deposition of granular tin oxide by atmospheric-pressure chemical vapor deposition. Progress toward module fabrication at the end of six months has been good, with the demonstration of 5.4% initial efficiency in a silicon/silicon multijunction submodule with an aperture area of 4620 cm{sup 2} and incorporating devices with 2nd-junction i-layer thicknesses of about 3500 {angstrom}. We also demonstrated a single-junction silicon submodule with an aperture area of 4620 cm{sup 2}, a thickness of about 3500 {angstrom}, and an initial efficiency of 6.5%. 4 refs., 39 figs., 5 tabs.