| Autor: |
Bothra U; Department of Chemistry, University of Washington, Seattle, Washington 98195, United States., Westbrook RJE; Department of Chemistry, University of Washington, Seattle, Washington 98195, United States., Liu Y; Department of Chemistry, University of Washington, Seattle, Washington 98195, United States., Wang J; Department of Chemistry, University of Washington, Seattle, Washington 98195, United States., Ziffer ME; Department of Physics, Columbia University, New York, New York 10027, United States., Ginger DS; Department of Chemistry, University of Washington, Seattle, Washington 98195, United States. |
| Abstrakt: |
We use electroabsorption (EA) spectroscopy to probe the charge transfer (CT) character in neat films and blends of donors and acceptors of interest for organic electronic applications. In particular, we compare the CT character in two polymer donor and non-fullerene acceptor blends, including 3,9-bis(2-methylene-((3-(1,1-dicyanomethylene)-6,7-difluoro)-indanone))-5,5,11,11-tetrakis(4-hexylphenyl)-dithieno[2,3- d :2',3'-d']- s -indaceno[1,2- b :5,6- b ']dithiophene (IT-4F) and 2,2'-((2 Z ,2' Z )-((12,13-bis(2-ethylhexyl)-3,9-diundecyl-12,13-dihydro-[1,2,5]thiadiazolo[3,4- e ]thieno[2″,3″:4',5']thieno[2',3':4,5]pyrrolo[3,2- g ]thieno[2',3':4,5]thieno[3,2- b ]indole-2,10-diyl)bis(methanylylidene))bis(5,6-difluoro-3-oxo-2,3-dihydro-1 H -indene-2,1-diylidene))dimalononitrile (Y6). Like classic polymer/fullerene blends, the blend based on IT-4F exhibits primarily first derivative-like EA features, suggesting localized exciton formation upon photoexcitation. However, the Y6-based blend has an EA spectrum that is dominated by second derivative-like features, consistent with CT character. We show that this signal originates primarily from Y6. We find that Y6 exhibits the highest dipole moment change (7.5 ± 2.5 D) of the molecules that comprise this study, consistent with a high degree of the CT character, and a relatively large polarization volume of 361 ± 70 Å 3 , consistent with strong electron delocalization. These results point to the origins of exceptional performance of organic photovoltaics (OPVs) based on Y6. |
