Engineered exciton diffusion length enhances device efficiency in small molecule photovoltaics
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In organic photovoltaic blends, there is a trade-off between exciton harvesting and charge extraction because of the short exciton diffusion length. Developing a way of increasing exciton diffusion length would overcome this trade-off by enabling efficient light harvesting from large domains. In this work, we engineered (enhanced) both exciton diffusion length and domain size using solvent vapour annealing (SVA). We show that SVA can give a three-fold enhancement in exciton diffusion coefficient (D) and nearly a doubling of exciton diffusion length. It also increases the domain size, leading to enhancement of charge extraction efficiency from 63 to 89%. Usually larger domains would reduce exciton harvesting but this is overcome by the large increase in exciton diffusion, leading to a 20% enhancement in device efficiency.
Sajjad , M T , Blaszczyk , O , Krishnan Jagadamma , L , Roland , T , Chowdhury , M , Ruseckas , A & Samuel , I D W 2018 , ' Engineered exciton diffusion length enhances device efficiency in small molecule photovoltaics ' , Journal of Materials Chemistry A , vol. 6 , no. 20 , pp. 9445-9450 . https://doi.org/10.1039/C8TA01226A
Journal of Materials Chemistry A
© 2018 the Author(s). This work has been made available online in accordance with the publisher’s policies. This is the author created, accepted version manuscript following peer review and may differ slightly from the final published version. The final published version of this work is available at https://doi.org/10.1039/C8TA01226A
DescriptionFunding: European Research Council (grant 321305). IDWS acknowledges a Royal Society Wolfson Research Merit Award. We are grateful to EPSRC for equipment grant (EP/L017008/1) and for support of OB (EP/M508214/1).
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