Engineered exciton diffusion length enhances device efficiency in small molecule photovoltaics
Abstract
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.
Citation
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
Publication
Journal of Materials Chemistry A
Status
Peer reviewed
ISSN
2050-7488Type
Journal article
Description
Funding: 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).Collections
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