APPARENT GETTERING OF THE STAEBLER-WRONSKI EFFECT IN AMORPHOUS-SILICON SOLAR-CELLS

The stability behaviour of intrinsic amorphous silicon materials incor porated in a p(+)-i-n(+) solar cell structure is considerably differen t from that observed by electrical characterization methods in individ ual thin films. This is due to the fundamental difference in Fermi-lev el position in a single layer compared to the situation occurring in d evices. We have employed the differences in the re-equilibration behav iour that have been observed in various intrinsic materials when the F ermi-level is shifted towards the valence band edge, in order to desig n a cell with a new profiled i-layer which would possess an improved e lectric field distribution after light soaking compared to cells with a constant i-layer. The contribution of the interface region to the st abilized conversion efficiency is greatly improved, whereas the first 50 nm of the cell structure remains unchanged. Thus, it appears that t he Staebler-Wronski effect is gettered away from the junction, much li ke the impurity gettering concept in crystalline solar cells.