On the modeling of dispersive transient photocurrent response of organic solar cells

Zhang D.
Allagui A.
Elwakil A.S.
Nassef A.M.
Rezk H.
Cheng J.
Choy W.C.H.

The current methods used for estimating the electrical parameters of organic solar cells (OSC) from time-domain measurements are based on integer-order impedance models. Meanwhile, in the frequency-domain, the adopted circuit models usually contain a constant phase element which is known to capture effectively the fractional-order dispersive behavior of these devices. Therefore, inconsistency arises between the two analyses. In this work, we derive the time-domain relaxation response of an OSC, found to follow a Mittag-Leffler function, using the same fractional-order impedance model. The classical integer-order model that results into the exponential decay of the photocurrent can be easily recovered and should be used as a valid approximation only when the dispersion coefficient is close to unity. © 2019 Elsevier B.V.