Determination of the minority carrier diffusion length in compositionally graded Cu ( In , Ga ) Se 2 solar cells using electron beam induced current

A method is proposed and tested which allows for the accurate determination of the carrier collection efficiency and minority carrier diffusion length in Cu ( In , Ga ) Se 2 solar cells using energy dependent electron beam induced current. Gallium composition gradients across the film thickness introduce quasielectric fields that are found to improve collection efficiency when they are located toward the rear of the sample. The quasielectric fields are also shown to reduce the influence of back surface recombination. The strengths and limitations of this technique are discussed and compared with external quantum efficiency measurements.