What parameters can be reliably deduced from the current-voltage characteristics of an organic bulk-heterojunction solar cell?

Abstract

Through the analysis of scales and simplification of the drift-diffusion device model, we have obtained a quantitative description of the mechanisms underlying the current-voltage (j-V) characteristics of organic bulk-heterojunction solar cells. The mechanisms have been resolved into the competition between the photogeneration, recombination, and extraction/injection rates, which determines the bulk charge carrier concentration; and the combined effect of the built-in field and the boundary layers in shaping the electric potential distribution, which determines the bulk field. The relationships between the j-V characteristics and standard model parameters have been captured with analytical expressions and verified through 1-D numerical simulations. We have determined that while the charge carrier generation rate can be reliably extracted with the device model from j-V measurements alone, the effective density of states and built-in potential, and the mobility and recombination prefactor are clustered pairs that can only be decoupled through other characterization techniques

Opto-electronic characterization of third-generation solar cells

“…We showed in a previous publication that fitting JV-curves is clearly insufficient to unambiguously determine physical parameters [ 9 ]. Our conclusions are consistent with Set et al demonstrating that parameter extraction from JV-curve fits are arbitrary [ 119 ]. The parameters are correlated – parameter 1 can have the same influence on the JV-curve as parameter 2.…”

A New Figure of Merit for Organic Solar Cells with Transport-limited Photocurrents

“…Y.T. Set et al derived a set of implicit equations taking into account second order recombination, which yielded JV -curves in good agreement to the results from 1D drift-diffusion (1D DD) simulations 7 . Ibrahim and coworkers provided explicit analytical expressions to describe the JV -curves of bulk heterojunction solar cells in the limit of uniform bimolecular recombination rates 8 .…”

Organic Optoelectronic Materials: Mechanisms and Applications

“…Device modeling efforts focused on simulations of J – V characteristics in solar cells ,,− or SCLC-regime diodes , and time-resolved photocurrents ,− using various modifications of the semiconductor drift-diffusion model adapted for a particular material and device geometry. A comprehensive review of device modeling of organic BHJ solar cells can be found in ref .…”