Oxygen-dependent photophysics and photochemistry of prototypical compounds for organic photovoltaics: inhibiting degradation initiated by singlet oxygen at a molecular level

Mikkel Bregnhøj, Michela Prete, Vida Engmann, Anne Ugleholdt Petersen, Mogens Brøndsted Nielsen, Morten Madsen, Peter R. Ogilby*

*Corresponding author for this work

Research output: Contribution to journalJournal articleResearchpeer-review

Abstract

Photo-initiated, oxygen-mediated degradation of the molecules in the active layer of organic photovoltaic, OPV, devices currently limits advances in the development of solar cells. To address this problem systematically and at a molecular level, it is informative to quantify the kinetics of the pertinent processes, both in solution phase and in solid films. To this end, we examined the oxygendependent photophysics and photochemistry of selected functionalized fullerenes, thiophene
derivatives, and a subphthalocyanine commonly used in OPV devices. We find that the photosensitized production of singlet molecular oxygen, O2(a1 Δg), by these molecules is a key step in the degradation process. We demonstrate that the addition of either β-carotene or astaxanthin as antioxidants can inhibit degradation by a combination of three processes: (a) deactivation of O2(a1 Δg)
to the oxygen ground state, O2(X3 Σg−), (b) quenching of the O2(a1 Δg) precursor, and (c)sacrificial reactions of the carotenoid with free radicals formed in the photo-initiated reactions. For OPV systems in which reaction with O2(a1
Δg) contributes to the degradation, the first two of these processes are desired and should have appreciable impact in prolonging the longevity of OPV devices
because they do not result in a chemical change of the system.
Original languageEnglish
Article number014001
JournalMethods and Applications in Fluorescence
Volume8
Issue number1
Number of pages16
ISSN2050-6120
DOIs
Publication statusPublished - Jan 2020

Keywords

  • Singlet Oxygen
  • Organic photovoltaic
  • oxidative degradation
  • beta Carotene

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