Effect of annealing on exciton diffusion in a high performance small molecule organic photovoltaic material
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Singlet exciton diffusion was studied in the efficient organic photovoltaic electron donor material DTS(FBTTh2)2. Three complementary time-resolved fluorescence measurements were performed: quenching in planar heterojunctions with an electron acceptor; exciton-exciton annihilation; and fluorescence depolarization. The average exciton diffusivity increases upon annealing from 1.6 × 10-3 cm2 s-1 to 3.6 × 10-3 cm2 s-1, resulting in an enhancement of the mean two–dimensional exciton diffusion length (LD=√4Dτ) from 15 nm to 27 nm. About 30% of the excitons get trapped very quickly in as-cast films. The high exciton diffusion coefficient of the material leads to it being able to harvest excitons efficiently from large donor domains in bulk heterojunctions.
Long , Y , Hedley , G J , Ruseckas , A , Chowdhury , M , Roland , T J , Serrano , L , Cooke , G & Samuel , I D W 2017 , ' Effect of annealing on exciton diffusion in a high performance small molecule organic photovoltaic material ' Applied Materials & Interfaces , vol 9 , no. 17 , pp. 14945-14952 . DOI: 10.1021/acsami.6b16487
Applied Materials & Interfaces
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