1,8-diiodooctane acts as a photo-acid in organic solar cells

Doumon, N. Y., Wang, G., Qiu, X., Minnaard, A., Chiechi, R. & Koster, L., 13-Mar-2019, In : Scientific Reports. 9, 14 p., 4350.

Research output: Contribution to journalArticleAcademicpeer-review

The last decade saw myriad new donor polymers, among which benzodithiophene-co-thienothiophene polymers are attractive due to their relatively high power conversion efficiency in bulk heterojunction solar cells. We examine the effect of UV-light on the stability of these polymers. The relationship between the polymer chemical structure and the UV-stability of the cells is explored on the one hand, and on the other hand, the effect of additives on their UV-stability: 1,8-diiodooctane against 1-chloronaphthalene in the cells and 1,8-octanedithiol in solution. For example, PBDTTT-E with 18% efficiency loss is more stable than PBDTTT-ET with 36% loss throughout the exposure. While 1,8-diiodooctane acts as photo-acid and leads to accelerated degradation of the solar cells, 1-chloronaphthalene does not. Acidity is known to be detrimental to the efficiency and stability of organic solar cells. The degradation is initiated upon UV-irradiation by the cleavage of the side chains, resulting in more electron traps and by the formation of iodine, dissolved HI and carbon-centered radicals from 1,8-diiodooctane as revealed by 1H NMR spectrum. The 1,8-octanedithiol spectra do not show such species. Finally, the mechanisms behind the effect of 1,8-diiodooctane are explained, paving the way for the design of new, efficient as well as stable materials and additives.
Original languageEnglish
Article number4350
Number of pages14
JournalScientific Reports
Publication statusPublished - 13-Mar-2019


  • optoelectronic devices, Organic photovoltaics, Photodegradation, photo-acid, diiodooctane, CONJUGATED POLYMERS, EFFICIENCY, PERFORMANCE, MORPHOLOGY, STABILITY, ADDITIVES, PHOTOSTABILITY, DEGRADATION, FULLERENES, ACCEPTOR

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