Abstract
The dynamics of photoluminescent response during optical degradation of MEH-PPV in films and chloroform solutions were investigated using various spectroscopic techniques (PL, UV-Vis, FTIR, and XRF). A significant blue shift in photoluminescence (PL) from MEH-PPV films during degradation indicated strong interchain exciton migration and a different photochemical reaction from that of solution. Two distinct wavelength-dependent dynamic PL responses were observed in MEH-PPV, and were attributed to photoactivation in the long side chain and polymer backbone. It was verified by a control experiment with BDMO-PPV which has symmetric side chains. The dynamic PL results indicate that the degradation process involves at least two-step photochemical reactions in the side chain and backbone. We also found that chlorine showed no effect on the optical degradation process.
Highlights
The study of MEH-PPV, Poly[2-methoxy-5-(2-ethylhexyloxy)1,4-phenylenevinylene], has been of great interest for its semiconducting properties
We have investigated the dynamics of the PL response during optical degradation in MEH-PPV organic semiconductor materials by utilizing PL, UV-Vis, X-ray fluorescence (XRF), and Fourier-transform infrared spectroscopy (FTIR) measurements
Chlorine plays no chemical role in the degradation process of MEH-PPV in chloroform solution or as a thin film
Summary
The study of MEH-PPV, Poly[2-methoxy-5-(2-ethylhexyloxy)1,4-phenylenevinylene], has been of great interest for its semiconducting properties. The degradation process of film has been studied more closely since device failure occurs in thin films of MEH-PPV. This study confirms the previous data and further explains the different mechanisms responsible for the degradation of MEH-PPV in thin films and solutions. The cuvette of MEH-PPV solution was degraded using the same laser beam at the intensity of 120 mW/cm[2]. The film was vacuum dried for 2 hours and an FTIR spectrum was measured before it was degraded. The film was degraded for 4 hours by the laser beam and an FTIR spectrum was collected again. The cuvette of the MEH-PPV solution was degraded using the laser beam at the intensity of 120 mW/cm[2] for 4 hours.
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