Anni M, Caruso M E, Lattante S, Cingolani R
National Nanotechnology Laboratory of CNR-INFM, Dipartimento di Ingegneria dell'Innovazione, Università degli Studi di Lecce, Via per Arnesano, 73100 Lecce, Italy.
J Chem Phys. 2006 Apr 7;124(13):134707. doi: 10.1063/1.2179795.
We investigated the temperature dependence of the poly(9,9-dioctylfluorene) beta phase photoluminescence (PL) spectra in spin coated thin films from tetrahydrofuran solutions. As the temperature increases from 18 to 300 K a continuous blueshift of the 0-0 PL peak of about 25 meV and an increase of the peak full width at half maximum (FWHM) of about 49 meV are observed. We show that the PL spectra temperature dependence is not due to a temperature dependent average conjugation length, as often assumed, but instead it can be quantitatively explained in the frame of a thermal quasiequilibrium model for excitons in an inhomogeneously broadened excited states distribution. We demonstrate that the emission blueshift and broadening are mainly due to the increase of the excitons' temperature with the sample one. This effect is partially compensated by an increasing efficiency of the exciton energy migration. The interplay between these two processes quantitatively explains the observed temperature dependence of the PL peak energy and of its FWHM. On the contrary we show that the PL spectra are almost independent of the absorption blueshift with temperature.
我们研究了从四氢呋喃溶液旋涂制备的薄膜中聚（9,9 - 二辛基芴）β相光致发光（PL）光谱的温度依赖性。当温度从18 K升高到300 K时，观察到0 - 0 PL峰持续蓝移约25 meV，并且半高宽（FWHM）增加约49 meV。我们表明，PL光谱的温度依赖性并非如通常所认为的那样归因于与温度相关的平均共轭长度，而是可以在非均匀展宽激发态分布中激子的热准平衡模型框架内进行定量解释。我们证明发射蓝移和展宽主要是由于激子温度随样品温度升高所致。这种效应部分地被激子能量迁移效率的增加所补偿。这两个过程之间的相互作用定量地解释了观察到的PL峰能量及其FWHM的温度依赖性。相反，我们表明PL光谱几乎与吸收随温度的蓝移无关。
