Charge Recycling Mechanism through a Triplet Charge-Transfer State in Ternary-Blend Organic Solar Cells Containing a Nonfullerene Acceptor

Dongki Lee, Hyeongjin Hwang, Dong Hun Sin, Chaneui Park, Se Gyo Han, Jungho Mun, Jaebum Noh, Sung Hyuk Kim, Hyojung Kim, Hansol Lee, Chanwoo Lee, Junsuk Rho, Kilwon Cho, Mun Seok Jeong

Research output: Contribution to journalArticlepeer-review

Abstract

We investigated the side-group and backbone-extension effects of a push-pull conjugated polymer (CP) on the charge-generation mechanism in ternary-blend organic solar cells (OSCs) containing PC71BM and a nonfullerene acceptor (NFA, ITIC). Transient absorption spectroscopy results revealed that the CP extension increased the hole-transfer efficiency from ITIC to the CPs, inducing the formation of triplet (T1) excitons by nongeminate recombination (via triplet charge-transfer states, 3CT) because of the finely mixed morphologies. Particularly, the 3CT state relaxation to T1 excitons was efficiently suppressed by PC71BM in the ternary-blend films based on the side-group and backbone extended CPs. This caused the recycling of the free carriers generated by the hole transfer from ITIC to the CPs, thereby increasing the efficiency of the OSC having the optimized ternary-blend morphology. Our findings provide new insights on the mechanism of charge generation through the photoinduced hole transfer from NFAs to CPs.

Original languageEnglish
Pages (from-to)2610-2618
Number of pages9
JournalACS Energy Letters
Volume6
DOIs
StatePublished - 2021
Externally publishedYes

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