Transport mechanisms and effective Schottky barrier height of ZnO/a-Si:H and ZnO/μc-Si:H heterojunction solar cells

The impact of boron doping on the p-layer of thin film silicon solar cells is assessed by measuring the effective Schottky barrier height of ZnO/a-Si:H and ZnO/μc-Si:H heterojunctions. A deviation from ideal diode characteristics is revealed by an increase of ideality factor with doping concentration. Higher current densities and lower effective Schottky barriers are evaluated for higher doping levels, resulting in increasingly Ohmic behaviour. This is attributed to an enhancement of tunneling through a thinner depletion region, as supported by computer simulations. Extracted barriers are in the range of 0.7–1 eV for the heterojunctions with rectifying behaviour.