This paper demonstrates that the incorporation of an unoptimized, wide band gap a-SiC:H layer near the p-type emitter layer in addition to a graded bandgap ”buffer” layer, leads to improved fill factors and open circuit voltages, in spite of the increased number of recombination sites at the p/i heterojunction. The as deposited as a function of a-SiC:H thickness shows an optimum of 10.5 % at a thickness of 10 – 20 Å. We have further improved this type of cell by incorporating a reverse carbon graded p-type layer and have thus achieved efficiencies in excess of 11.0 %. The cells are all amorphous and do not comprise antireflective coatings or enhanced back reflectors. A new defect engineering scheme to accomplish enhanced stabilized efficiencies of amorphous silicon solar cells is also proposed here.
Comparison between textured SnO2:F and Mo contacts with the p-type layer in p–i–n hydrogenate amorphous silicon solar cells by forward bias impedance analysis