Research on High-Efficiency, Single-Junction, Monolithic, Thin-Film Amorphous Silicon Solar Cells: Phase 1, Annual Subcontract Report, February 1, 1987-January 31, 1988.

摘要

This document describes the progress made in obtaining stable, a-Si-based submodules that have a large area and high efficiency. Conversion efficiencies of up to 11.95% were obtained in small-area, single-junction a-Si solar cells using textured TiO(sub 2), superlattice p-layers, graded carbon concentrations near the p/i interface, and highly reflective ITO/silver back contacts. Single- junction a-SiC and a-SiGe p-i-n cells were also fabricated that had conversion efficiencies of 9%--11%, and some recently fabricated stacked-junction cells had conversion efficiencies of about 10%. In materials research boron-doped microcrystalline SiC films were recently developed containing up to 6 at. % carbon with conductivities of 3 (times) 10(sup (minus)3)/(Omega)-cm at room temperature and activation energies of 0.11 eV. Microcrystalline film growth was shown to be strongly influenced by the nature of the substrate, with nucleation occurring more readily on a-Si substrates than on TiO(sub 2). Stability studies show that light-induced degradation is usually enhanced by the presence of carbon grading near the p/i interface. In general, adding either germanium (from GeH(sub 4)) or carbon (from CH(sub 4)) to the i-layer of a p-i-n cell leads to enhanced light-induced degradation. 13 refs., 80 figs., 17 tabs.