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15 June 2001Two types of excitons in poly(p-phenylene-vinylene) thick film at high-density excited state
Two types of excitons with different dynamics are observed in poly(p-phenylene-vinylene) thick films pumped by the intense 0.2 ps light pulses. The films are prepared from soluble sulphonium polyelectrolyte precursor polymer using different thermolysis temperatures between 240 degrees Celsius and 350 degrees Celsius. Narrowing of emission spectra accompanied by lifetime shortening is observed in the films formed at low temperature thermolysis at 240 degrees Celsius and 300 degrees Celsius when the films are pumped at their absorption edge of 500 nm with high intensity pulses. Contrary to the spectral narrowing pumped at the absorption edge, no spectral narrowing occurs and the quenching of the emission is observed when the samples are pumped at their absorption peaks around 400 nm. Sufficient concentration of the excitons responsible for the luminescence is needed to obtain the spectral narrowing which can be attributed to both amplified spontaneous emission and cooperative radiation or superfluorescence. The quenching of photoluminescence without any spectral narrowing is ascribed to the quenching of excitons by photoproducts such as free carriers. We propose a novel application of the phenomena of the spectral narrowing and the quenching in PPV films as an optical logic element with an exclusive OR function.
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Shunsuke Kobayashi, Fumio Sasaki, Kazuhiro Murata, Takanobu Noguchi, Toshihiro Ohonishi, "Two types of excitons in poly(p-phenylene-vinylene) thick film at high-density excited state," Proc. SPIE 4279, Organic Photonic Materials and Devices III, (15 June 2001); https://doi.org/10.1117/12.429379