Photo-oxidation of electroluminescent polymers studied by core-level photoabsorption spectroscopy

Abstract

The C 1s and O 1s core-level photoabsorption spectra of poly͓2-methoxy,5-͑2Ј-ethyl-hexoxy͒-1,4-phenylene vinylene͔ ͑MEH-PPV͒ before and after exposure O 2 and broadband visible light were recorded to determine the degradation pathway for this polymer. The change in the O 1s spectra as a function of exposure demonstrates that the O adds to the polymer chain to form a carbonyl group. Exposure to only O 2 or only light causes no change in the C 1s or O 1s spectra. In the C 1s spectra, the change in the dependence on the photon angle of incidence after exposure demonstrates that O attacks the polymer at the double bond in the vinyl group thereby altering the extended conjugation of the polymer.

A new encapsulation solution for flexible organic solar cells

“…The mechanism involves the binding of oxygen atoms to vinyl bonds, which breaks the conjugation and leads to the formation of carbonyl groups [13,12]. Spectroscopic ellipsometry studies showed that during simultaneous exposure to air and light, the thickness of the active layer increases while its refractive index and absorption coefficient drastically decrease [14].…”

“…Conjugated polymers such as poly(p-phenylene vinylene) (PPV) are known to be rather unstable in air [11], being particularly susceptible to photodegradation induced by oxygen and moisture [12]. The mechanism involves the binding of oxygen atoms to vinyl bonds, which breaks the conjugation and leads to the formation of carbonyl groups [13,12].…”

Side‐Chain Degradation of Ultrapure π‐Conjugated Oligomers: Implications for Organic Electronics

“…Successful introduction of products into the market can be hampered by limited stability during processing and device operation, [11] and improved understanding of the degradation of active components in existing devices is consequently critical for the long-term success of emerging plastic electronics and putative (supra)molecular electronics. Many techniques have been applied to studies in this area; [12][13][14][15][16] in this work, the monodispersity and exceptionally high levels of oligomer purity available allow us to use matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) as the main probe; this and related powerful analytical techniques have only rarely been explored in this field. [17,18] We report results on the massspectrometric analysis of the degradation products of two monodisperse defect-free oligomers, a penta(9,9-dialkylfluorene) and an oligoethyleneglycol-substituted sexithiophene, giving direct insight into the mechanism of oxidative degradation of p-conjugated materials.…”

Microfabrication of electroluminescent polymer for devices construction

“…5, in which the black line represents the absorption spectrum for a sample that was not micromachined. As it can be seen, the absorption band centered at 500 nm ( → * electronic transition of MEH-PPV [30,31]) decreases with the energy of the pulse used in the micromachining [14], indicating a photobleaching of the sample upon fs-laser exposure [32,33]. Such changes in the MEH-PPV absorption spectrum have been attributed to photo-oxidation [6].…”