Department of Physics, CNRS Ewha International Research Center, Ewha Womans University, Seoul, Korea.
Phys Chem Chem Phys. 2013 Feb 28;15(8):2867-72. doi: 10.1039/c2cp43705h. Epub 2013 Jan 22.
We report on singlet-singlet annihilation and exciton diffusion in as-prepared p-type and annealed n-type thin films of the low-bandgap quinoidal quaterthiophene [QQT(CN)4] using ultrafast transient absorption measurements. The decay dynamics of exciton populations are well described by a one-dimensional diffusion-limited bimolecular recombination, indicating that the singlet excitons migrate preferentially along the stacking direction. Our results show that the exciton diffusion constants in QQT(CN)4 films do not vary significantly upon thermal annealing. Exciton diffusion lengths are measured to be as high as 4 and 5 nm in as-prepared and annealed QQT(CN)4 films, respectively. We also observe an influence of the excitation densities on the singlet exciton diffusion, which is attributed to phonon scattering. Because of the possibility of patterning p-n regions in QQT(CN)4 films by thermal nanolithography techniques, this study provides important insight not only into the photophysical properties of quinoidal oligothiophene derivatives but also for their future integration into high-performance p-n nanostructured near infrared light-sensing devices.
我们使用超快瞬态吸收测量报告了低带隙醌式四噻吩[QQT（CN）4]的制备的 p 型和退火的 n 型薄膜中的单重态-单重态湮灭和激子扩散。激子种群的衰减动力学很好地描述为一维扩散限制的双分子复合，表明单重激子优先沿着堆积方向迁移。我们的结果表明，在热退火过程中，QQT（CN）4 薄膜中的激子扩散常数没有显著变化。在制备的和退火的 QQT（CN）4 薄膜中，激子扩散长度分别高达 4nm 和 5nm。我们还观察到激发密度对单重激子扩散的影响，这归因于声子散射。由于通过热纳米光刻技术在 QQT（CN）4 薄膜中形成 p-n 区的可能性，这项研究不仅为醌式寡噻吩衍生物的光物理性质提供了重要的见解，而且为它们未来集成到高性能 p-n 纳米结构近红外光感应器件中提供了重要的见解。
