We report on the effectiveness of two methods for recovering the density of electronic states from transient photocurrent data, one employing an exact solution of the Laplace transformed multiple-trapping rate equations and one a Tikhonov regularization technique. In order to evaluate these methods for recovery of energetically broad and narrower distributions of states we have applied each to data obtained from plasma-enhanced chemical vapor deposition (PECVD) a-Si:H films subjected to progressive light soaking and also to a single crystal sample of tin-doped crystalline CdTe. Both methods are found to perform equally well in terms of accuracy and resolution but the exact method is more sensitive to noise on the input data. A featureless increase in defect density in the PECVD a-Si:H film of a factor of 5–10 is observed on light soaking. Preliminary analysis of the CdTe:Sn data indicates the presence of two narrow bands of states, approximately 0.15 and 0.36 eV below the conduction band edge.
Gueorguieva, M. J., Main, C., Reynolds, S., Bruggemann, R., & Longeaud, C. (2002). Probing localized states distributions in semiconductors by Laplace transform transient photocurrent spectroscopy. Journal of Non-Crystalline Solids, 299, 541-545. https://doi.org/10.1016/S0022-3093(01)00967-x