Probing Charge Transfer Character in Modern Donor/Acceptor Materials via Electroabsorption Spectroscopy

• DOI: 10.1021/acs.jpclett.3c03262
• Publication Date: 2024-01-27T00:48:35Z
• Authors: Urvashi Bothra; Robert J. E. West...; Yun Liu; Jian Wang; Mark E. Ziffer; David S. Ginger
• Keywords: Acceptor; Photoexcitation; Methylene

We use electroabsorption (EA) spectroscopy to probe the charge transfer (CT) character in neat films and blends of donors acceptors interest for organic electronic applications. In particular, we compare CT two polymer donor 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) 2,2′-((2Z,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-1H-indene-2,1-diylidene))dimalononitrile (Y6). Like classic polymer/fullerene blend based on IT-4F exhibits primarily first derivative-like EA features, suggesting localized exciton formation upon photoexcitation. However, Y6-based has an spectrum that is dominated by second consistent with character. show this signal originates from Y6. find Y6 highest dipole moment change (7.5 ± 2.5 D) molecules comprise study, a high degree character, relatively large polarization volume 361 70 Å3, strong electron delocalization. These results point origins exceptional performance photovoltaics (OPVs)