Light-induced degradation of a push–pull copolymer for ITO-free organic solar cell application

Newayemedhin A. Tegegne, Hailemariam Wendimu, Zelalem Abdissa, Wendimagegn Mammo, Mats R. Andersson, Fekadu Gashaw Hone, Dinsefa M. Andoshee, Olufemi Olaoye, Gurthwin Bosman

Research output: Contribution to journalArticlepeer-review

10 Citations (Scopus)


A push–pull copolymer-P1 was successfully designed and synthesized by coupling ter-thiophene donor (D) and isoindigo acceptor (A) units by a direct arylation polycondensation method. The optical bandgap of the copolymer was 1.51 eV. The copolymer showed a weak intramolecular charge transfer due to steric hindrance between the D and A units. An ITO-free organic solar cell was fabricated based on P1 donor and PC71BM acceptor. An almost complete bleaching of absorption in less than 50 h of light exposure was found in pristine P1 film. This fast light-induced degradation is due to chain scissioning and intramolecular bond breaking within the single copolymer unit. This degradation is suppressed with the addition of PC71BM. However, the addition of a 3% v/v 1,8-diiodooctane solvent additive in the processing solvent reduces the life time of the P1:PC71BM-based active layer that the remaining absorbance decreases from 30 to 10% after 80 h of light exposure.

Original languageEnglish
Pages (from-to)21303-21315
Number of pages13
JournalJournal of Materials Science: Materials in Electronics
Issue number23
Early online date19 Oct 2020
Publication statusPublished - Dec 2020
Externally publishedYes


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