Table 6

Sensitivity of the pm-Si:H solar cell output to the ZnO:Al/P-μc-SiO_x:H surface band bending. The case where the sbb = 0.2 eV (that is generally observed for ZnO:Al/P-a-SiC:H), is given in the first row of this table and assumed for the single window designs in Table 4. The front contact barrier height (ϕ_b0) for this case is 1.83 eV, since the band gap of P-μc-SiO_x is taken to be 2.5 eV and its activation energy = 0.47 eV. Even for a slight increase of sbb – to 0.3 eV (ϕ_b0 = 1.73 eV), V_oc, FF and the cell efficiency deteriorate appreciably (second line of table), as the V_bi falls. Any effort to increase the V_bi by increasing the P-μc-SiO_x:H thickness, brings down the J_sc. The third line indicates the effect of having ϕ_b0 = 1.32 eV, the same as at the ZnO:Al/P-μc-Si:H interface of the double window design.