Mikhnenko O V, Cordella F, Sieval A B, Hummelen J C, Blom P W M, Loi M A
Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands.
J Phys Chem B. 2008 Sep 18;112(37):11601-4. doi: 10.1021/jp8042363. Epub 2008 Aug 26.
The temperature dependence of the exciton dynamics in a conjugated polymer is studied using time-resolved spectroscopy. Photoluminescence decays were measured in heterostructured samples containing a sharp polymer-fullerene interface, which acts as an exciton quenching wall. Using a 1D diffusion model, the exciton diffusion length and diffusion coefficient were extracted in the temperature range of 4-293 K. The exciton dynamics reveal two temperature regimes: in the range of 4-150 K, the exciton diffusion length (coefficient) of approximately 3 nm (approximately 1.5 x 10 (-4) cm2/s) is nearly temperature independent. Increasing the temperature up to 293 K leads to a gradual growth up to 4.5 nm (approximately 3.2 x 10 (-4) cm2/ s). This demonstrates that exciton diffusion in conjugated polymers is governed by two processes: an initial downhill migration toward lower energy states in the inhomogenously broadened density of states, followed by temperature activated hopping. The latter process is switched off below 150 K.
利用时间分辨光谱研究了共轭聚合物中激子动力学的温度依赖性。在含有尖锐聚合物 - 富勒烯界面的异质结构样品中测量了光致发光衰减，该界面充当激子淬灭壁。使用一维扩散模型，在4 - 293 K的温度范围内提取了激子扩散长度和扩散系数。激子动力学揭示了两个温度区域：在4 - 150 K范围内，激子扩散长度（系数）约为3 nm（约1.5×10^(-4) cm²/s）几乎与温度无关。将温度升高到293 K会导致激子扩散长度逐渐增长至4.5 nm（约3.2×10^(-4) cm²/s）。这表明共轭聚合物中的激子扩散受两个过程支配：在非均匀展宽的态密度中向较低能量状态的初始下坡迁移，随后是温度激活跳跃。后一个过程在150 K以下关闭。
