Quantifying the Excitonic Static Disorder in Organic Semiconductors

Abstract

AbstractOrganic semiconductors are disordered molecular solids, and as a result, their internal charge generation dynamics, charge transport dynamics, and ultimately, the performance of the optoelectronic devices they constitute, are governed by energetic disorder. This is particularly pertinent for emerging photovoltaic technology where the extractable power is directly dependent on these dynamics. To ascertain how energetic disorder impacts charge generation, exciton transport, charge transport, and the performance of organic semiconductor devices, an accurate approach is first required to measure this critical parameter. In this work, it is shown that the static disorder of an organic semiconductor can be obtained from its photovoltaic external quantum efficiency spectrum at wavelengths near the absorption onset. A detailed methodology is presented, alongside a computational framework, for quantifying the static energetic disorder associated with singlet excitons. Moreover, the authors show that minimizing the limiting effects of optical interference is crucial for achieving high‐accuracy quantifications. Finally, transparent devices are employed to estimate the excitonic static disorder in several technologically relevant organic semiconductor donor–acceptor blends, including the high‐efficiency organic photovoltaic system PM6:Y6.