Linear and nonlinear optical spectroscopic characterisation of triphenylamine and 1,2,3-tris(3-methylphenylphenylamino)benzene
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- 作者：A.K. Bansal ; A. Penzkofer
- 关键词：Triphenylamine TPA ; Tris(3-methylphenylphenylamino)benzene m-MTDAB ; OLED hole-transport materials ; Neat films ; Absorption spectroscopy ; Fluorescence spectroscopy ; Reverse saturable absorption ; Attenuation/amplification of spontaneous emission ; Excited-sta
- 刊名：Chemical Physics
- 出版年：2008
- 出版时间：3 September 2008
- 年：2008
- 卷：352
- 期：1-3
- 页码：48-56
- 全文大小：368 K
文摘
The molecule triphenylamine (TPA) in tetrahydrofuran (THF) and the starburst triphenylamine oligomer 1,3,5-tris(3-methylphenylphenylamino)benzene (m-MTDAB) in THF and as neat film are characterized. Absorption and emission spectroscopic parameters are determined. The S0–S1 transition is found to be weak (nπ* transition) with small fluorescence quantum yield and efficient non-radiative decay (singlet–triplet intersystem crossing). The S0–S1 absorption cross-section spectra in the tails of the broad first absorption bands of the compounds are separated out by radiative lifetime determination and applying the mirror-image relation between absorption and emission. Excimer formation is observed for m-MTDAB neat films, its photo-dynamics is studied, and monomer and excimer stimulated emission cross-section spectra are extracted. Reverse saturable absorption is observed for TPA and m-MTDAB in picosecond laser nonlinear transmission measurements (laser duration 35 ps, laser wavelength 347.15 nm) and the responsible excited-state absorption cross-sections are determined. A new method is developed to calculate the excited-state absorption cross-section spectra of the samples in the fluorescence spectral region by amplification/attenuation of spontaneous emission measurements. The excited-state absorption is found to be larger than the stimulated emission for TPA in THF and for m-MTDAB films excluding their lasing ability. For m-MTDAB in THF the stimulated emission is found to be slightly larger than the excited-state absorption at the wavelength position of peak fluorescence emission.