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Impact of Aggregation on the Photochemistry of Fullerene Films: Correlating Stability to Triplet Exciton Kinetics
ACS Applied Materials & Interfaces, Volume: 9, Issue: 27, Pages: 22739 - 22747
Swansea University Authors: Catherine De Castro , Matthew Davies , Trystan Watson , James Durrant , Zhe Li , Wing Chung Tsoi
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DOI (Published version): 10.1021/acsami.7b03298
The photochemistry and stability of fullerene ﬁlms is found to be 11 strongly dependent upon ﬁlm nanomorphology. In particular, PC61BM blend ﬁlms, 12 dispersed with polystyrene, are found to be more susceptible to photobleaching in 13 air than the more aggregated neat ﬁlms. This enhanced photobleach...
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The photochemistry and stability of fullerene ﬁlms is found to be 11 strongly dependent upon ﬁlm nanomorphology. In particular, PC61BM blend ﬁlms, 12 dispersed with polystyrene, are found to be more susceptible to photobleaching in 13 air than the more aggregated neat ﬁlms. This enhanced photobleaching correlated 14 with increased oxygen quenching of PC61BM triplet states and the appearance of a 15 carbonyl FTIR absorption band indicative of fullerene oxidation, suggesting 16 PC61BM photo-oxidation is primarily due to triplet-mediated singlet oxygen 17 generation. PC61BM ﬁlms were observed to undergo photo-oxidation in air for even 18 modest (≤40 min) irradiation times, degrading electron mobility substantially, 19 indicative of electron trap formation. This conclusion is supported by observation of 20 red shifts in photo- and electro-luminescence with photo-oxidation, shown to be in 21 agreement with time-dependent density functional theory calculations of defect 22 generation. These results provide important implications on the environmental stability of PC61BM-based ﬁlms and devices.
fullerene ﬁlms, triplet exciton kinetics, PC61BM blend ﬁlms, photo-oxidation
Faculty of Science and Engineering