OPTICAL SPECTROSCOPY OF HIGHLY ORDERED POLY(P-PHENYLENE VINYLENE)

We report a study of the photophysical properties of poly(p-phenylene vinylene), PPV, prepared in a way that gives an especially high degree of intrachain order. Optical absorption, photoluminescence, photoindu ced absorption, and photoconductivity excitation spectra are presented and compared to data reported for less well ordered PPV. Spectral red shifts, sharpening of spectral lines, and a transfer of oscillator st rength into the vibronic ground states of the electronic transitions a re observed. Photoinduced absorption due to long-lived charged excitat ions, previously reported for less ordered PPV. could not be detected in this material. Photoconductivity excitation spectra show a steep ri se at the absorption edge with no appreciable offset between the onset s for photoconduction and absorption. A very slow photocurrent compone nt is observed, which we associate with the trapping and subsequent th ermal release of photocarriers.