New Insights into the Mechanisms of Photodegradation/Stabilization of P3HT:PCBM Active Layers Using Poly(3-hexyl-d13-Thiophene)

Aurelien Tournebize, Pierre-Olivier Bussiere, Agnes Rivaton, Jean-Luc Gardette, Hussein Medlej, Roger C. Hiorns, Christine Dagron-Lartigau, Frederik C Krebs, Kion Norrman

Research output: Contribution to journalJournal articleResearchpeer-review

Abstract

The photo-oxidation mechanism of thin-film blends based on poly(3-hexylthiophene):phenyl-C-61-butyric acid methyl ester (P3HT:PCBM) upon irradiation with ultraviolet-visible light (UV-Vis) was studied. The use of deuterated P3HT, i.e., poly(3-hexyl-d(13)-thiophene) (P3HdT), permitted discrimination of carbon originating from the hexyl-d(13) chain and carbon originating from PCBM and the nondeuterated thiophene unit. The photo-oxidation of both components of the blend was monitored using the combination of various analytical techniques to probe the bulk and the surface of the deposits. The results show that the stabilization of P3HT by PCBM is due to a morphological reorganization between P3HT and PCBM. This change occurs at a low temperature (ca. 42 degrees C) and increases the lifetime of the primary property, i.e., the ability of the active layer to absorb light. However, this is counterbalanced by the enhanced formation of oxidized PCBM molecules, which may act as electrons traps. It is shown that UV light is harmful for P3HT, PCBM, and P3HT:PCBM blend stabilities, even if PCBM provides a filter effect that is strongest at short wavelengths. It is proposed that the photochemical behavior of the chromophoric species involved in the chain radical oxidation of P3HT is a key characteristic in the underlying mechanism. The results obtained in this work advance the understanding of active layer stability and will help improve the design of long lifetime organic solar cells thanks to the use of cutoff filter in the substrate or encapsulation of the devices.
Original languageEnglish
JournalChemistry of Materials
Volume25
Issue number22
Pages (from-to)4522-4528
Number of pages7
ISSN0897-4756
DOIs
Publication statusPublished - 2013

Keywords

  • CHEMISTRY,
  • MATERIALS
  • PHOTOELECTRON-SPECTROSCOPY
  • PCBM BLENDS
  • THIN-FILMS
  • MDMO-PPV
  • POLYMER
  • POLY(3-HEXYLTHIOPHENE)
  • DEGRADATION
  • OXYGEN
  • PHOTOOXIDATION
  • ABSENCE
  • poly(3-hexythiophene) (P3HT)
  • phenyl-C-61-butyric acid methyl ester (PCBM)
  • P3HT:PCBM
  • isotopic labeling
  • photo-oxidation
  • photochemical behavior
  • morphology
  • organic photovoltaics
  • Butyric acid
  • Carbon
  • Chains
  • Esterification
  • Esters
  • Light
  • Morphology
  • Oxidation
  • Thiophene
  • Active filters
  • Isotopic labeling
  • Methyl esters
  • Organic photovoltaics
  • Photochemical behaviors
  • Poly(3-hexythiophene)
  • phenyl-C61-butyric acid methyl ester (PCBM)

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