Collection length of holes in a-Si:H by surface photovoltage using a liquid Schottky barrier

In a surface photovoltage determination of the collection length of holes in undoped amorphous Si:H, the ac surface photovoltage has been picked up by the use of a liquid Schottky barrier. The redox couple quinone-hydroquinone proved the best liquid. Simultaneous illumination with a bias light of up to 1 sun removes most of the internal barrier field allowing measurement of the ambipolar diffusion length. Values in the range 0.01–0.8 μm are found depending on the conditions of sample preparation.