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为探讨洞悉电场对有机发光二极管电致荧光量子效率的影响,通过激发-探测超快光谱技术研究了激子在电场下的瞬态行为.与单重态激子相应的激发态在230μJ/cm2激发强度下,显示了快慢两个弛豫过程.快慢组分的权重因子及快组分弛豫时间常数是电场相关的,在6.4×105V/cm的电场下,与无偏置电场相比,激子的快组分弛豫时间加速,快组分的权重因子由22%增加为72%,约50%的初始激子又通过电场而离解.慢组分是电场无关的,其弛豫时间常数为890ps.实验结果还揭示了由激发光所产生的长程声学声子,其声速为17/ps.
In order to explore the effect of electric field on the quantum efficiency of electroluminescence of organic light-emitting diodes, the transient behavior of excitons under electric field was studied by using excitation-detection ultrafast spectroscopy.The excited states corresponding to singlet excitons were at 230μJ / cm2 Under the excitation intensity, the two relaxation processes show the fast and slow relaxation processes.The weighting factors and the fast relaxation time constants of the fast and slow components are electric field dependent, and under the electric field of 6.4 × 105V / cm, compared with the unbiased electric field, The fast component relaxation time of the exciton accelerates, the weight factor of the fast component increases from 22% to 72%, and about 50% of the initial excitons in turn dissociate through the electric field. The slow component is electric field independent and its relaxation time The constant is 890 ps. The experimental results also reveal the long-range acoustic phonon produced by the excitation light with a sound velocity of 17 cm / ps.