Mobility and optical gaps in different a-Si:H based materials and their impact on cell performance

This work investigates the correlation between the "mobility gaps" (E/sub /spl mu//) and the "optical gaps" (E/sub OPT/) of a-Si:H materials and the open circuit voltages (V/sub oc/) of their standard solar cell structures. The study was carried on both RF and DC glow discharge materials using p-i-metal Schottky barrier and p-i-n cell structures having abrupt junctions formed with p-a-Si:C,H layers. Because the correlation between E/sub OPT/ and E/sub /spl mu// in amorphous materials has not been established, a self-consistent approach is presented here which can be applied to both a-Si:H and a-Si:C,H materials. The self-consistency of the E/sub /spl mu// results obtained using internal photoemission with the activation energies of the dark reverse currents in the p-i-metal structures is also presented. It is found that hydrogen dilution has a large effect on "displacing" E/sub /spl mu// further away from E/sub OPT/, which is consistent with higher V/sub oc/ observed with such materials.