The Time-of-Flight Technique Applied to Amorphous Silicon Pin Solar Cells

Abstract

ABSTRACTFast transient photocurrent measurements have been performed on a-Si:H based pin diodes with thicknesses down to 0.5 μm. On a thick sample drift mobilities derived in either the small-signal or the space-charge limited current mode are compared. On real solar cell devices in SCL voltage (integral) Mode the electron lifetimes τ are determined from the extraction time of the photo-generated charge in dependence on the degradation state of the sample. A clear and reproducible correlation between lifetime and degradation state has experimentally been established. Lifetimes τ, for which an intensity dependence has been observed in the SCL voltage Mode, are compared to the μτ-product from a small-signal charge collection Measurement. The influence of the real absorption profile on the measurements is discussed.