5 November 2002 Photo-EMF effect in polydiacetylene PTS
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In this work we report for the first time observation of AC photocurrents generated by photo-emf effect in high quality crystals of the conjugated polymer 2,4-hexadiyne-1,6-diol-bis-(para-toluene sulfonate) or polydiacetylene PTS (usually referred simply as PTS). We used illumination at λ=633nm where the absorption spectra has its peak. In principle, photocurrent at this wavelength should be small due to the large exciton binding energy, however we show that relative large photocurrents can be observed at modest electric fields (up 2000 V/cm). When the sample is illuminated with a periodically oscillating interference pattern it leads to spatial redistribution of charge carriers among traps. Spatial overlap of the resulting space-charge field with the oscillating photoconductivity pattern gives rise to an oscillating photocurrent (photo-emf signal). From photo-emf measurements, a Maxwell relaxation time of 0.17 sec at 6 W/cm2 and lifetime of carriers of 6 ms were estimated. The later was confirmed from photoconductivity measurements.
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Ruben Ramos-Garcia, V. Camacho-Pernas, Carlos G. Trevino-Palacios, George I. Stegeman, "Photo-EMF effect in polydiacetylene PTS", Proc. SPIE 4802, Organic Photorefractive and Photosensitive Materials for Holographic Applications, (5 November 2002); doi: 10.1117/12.452441; https://doi.org/10.1117/12.452441

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