Direct determination of doping concentration and built-in voltage from extraction current transients

We have extended the analytical framework of the charge extraction by linearly increasing voltage (CELIV) theory to the case with doping, taking the effect of built-in voltage, diffusion and band-bending into account. Not taking the built-in voltage into account in dark CELIV will lead to an underestimation of the charge carrier density, while the mobility is overestimated. Furthermore, based on the analysis we propose to use CELIV in the doping-induced capacitive regime for direct determination of doping concentration and built-in voltage from extraction current transients in the time-domain of doped thin-film semiconductor devices. The analytical framework is confirmed numerically with a one-dimensional drift-diffusion model and experimentally on aged P3HT:PCBM bulk heterojunction solar cell devices. An excellent agreement between the experimental extraction current transients and the analytical prediction is found. The presented analytical treatment is not limited to sandwich-type thin-film devices, but is more general and the technique can also be extended to pn-junctions. (C) 2014 Elsevier B.V. All rights reserved.