Abstract
In this paper, the spectral properties of a conjugated polymer poly [2-methoxy-5-(2-ethylhexyloxy)-1, 4-phenylenevinylene] (MEH-PPV) in benzene have been studied. The results showed that the fluorescence spectra of MEH-PPV under low concentrations had two peaks; the dominant one due to monomer was around 560 nm, and the shoulder one attributed to the excimer was around 600 nm. Under higher concentrations, it was found that there was only one band around 600 nm due to the excimeric state. By increasing the concentrations of MEH-PPV, it could be seen that there was a new band around 640nm. This band is being attributed to the double excimer. Under high power pulsed laser excitation, we observed amplified spontaneous emission (ASE) at 570 nm, 605 nm and 650 nm. These ASE peaks could arise from the monomer, excimer and double excimer states of the macromolecule respectively. To the best of our knowledge this is perhaps the first report on ASE from double excimer of the conjugated polymer, MEH-PPV in liquid solution.
Highlights
Many conjugated polymers are capable of light emission [1]
In many fluorescent organic molecules, light emission is severely quenched at high concentrations such as that typically found in solid films
It can be seen that when the concentration was increased up 1.0 μM, the result showed that the band around 600 nm, which was weaker at 0.1 μM, became comparable to that at 560 nm
Summary
Many conjugated polymers are capable of light emission [1]. This can be generated either optically, by shining light onto a sample to give fluorescence, or electrically, by applying a voltage to a polymer light-emitting diode [2]. There are several reasons why semiconducting polymers could be attractive laser materials [4]–[6]: The first is that there exists a range of polymers that can emit light across the visible spectrum. These polymers have broad spectra suitable for tunable lasers. In many fluorescent organic molecules (including laser dyes), light emission is severely quenched at high concentrations such as that typically found in solid films. With sufficient pump power, the ASE with a peak at 650 nm with FWHM of 8 nm could be obtained
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