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Quantifying the Excitonic Static Disorder in Organic Semiconductors
Advanced Functional Materials, Start page: 2113181
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Organic 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 emergin...
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Organic 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.
absorption coefficient, energetic disorder, excitons, external quantum efficiency, organic semiconductors, organic solar cells
College of Science
This work was funded through the Welsh Government’s Sêr Cymru II Program “Sustainable Advanced Materials” (Welsh European Funding Office − European Regional Development Fund). P.M. is a Sêr Cymru II Research Chair and A.A. is a Rising Star Fellow also funded through the Welsh Government’s Sêr Cymru II “Sustainable Advanced Materials” Program (European Regional Development Fund, Welsh European Funding Office, and Swansea University Strategic Initiative). This work was also funded by UKRI through the EPSRC Program Grant EP/T028511/1 Application Targeted and Integrated Photovoltaics.