Effect of germanium fraction on the effective minority carrier lifetime in thin film amorphous-Si/crystalline-Si1xGex/crystalline-Si heterojunction solar cells

The effect of germanium fraction on the effective minority carrier lifetime (tau(eff)) for epitaxial Si1-xGex layers is extracted using measurements on amorphous(a) Si(n+)/crystalline(c)-Si1-xGex(p)/crystalline(c)-Si(p+) heterojunction solar cells with x = 0.25, 0.41 and 0.56. The tau(eff) extracted for Si0.75Ge0.25 is similar to 1 mu s, decreasing to similar to 40 ns for Si0.44Ge0.56. In addition, the band-gap voltage offset (W-oc) increases from 0.5 eV for Si to 0.65 eV for 56% Ge indicating an increase in non-radiative recombination consistent with the reduction in effective lifetime. (C) 2013 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution 3.0 Unported License.