该【取向P3HT薄膜的稳态和皮秒瞬态各向异性研究 】是由【niuww】上传分享，文档一共【2】页，该文档可以免费在线阅读，需要了解更多关于【取向P3HT薄膜的稳态和皮秒瞬态各向异性研究 】的内容，可以使用淘豆网的站内搜索功能，选择自己适合的文档，以下文字是截取该文章内的部分文字，如需要获得完整电子版，请下载此文档到您的设备，方便您编辑和打印。取向P3HT薄膜的稳态和皮秒瞬态各向异性研究 Introduction: Poly(3-hexylthiophene) (P3HT) is a semiconducting polymer which has been widely used in organic solar cells, field-effect transistors, light-emitting diodes and other optoelectronics devices due to its good electronic properties, solution processability and easy modification. The anisotropic structure of P3HT films plays a critical importance in the performance of such devices. In this paper, we will study the steady-state and picosecond transient anisotropy of P3HT films, and explore the correlation between the structural anisotropy and the optical properties. Experimental: The P3HT films were deposited on glass substrate by a spin-coating method using chlorobenzene as the solvent. The thickness of the films was controlled by varying the rotational speed. The UV-Vis absorption spectra were recorded with a spectrophotometer. The steady-state anisotropy was measured by the polarization modulation technique with a steady-state fluorescence spectrometer. The excited-state anisotropy was measured by using picosecond time-resolved fluorescence up-conversion technique. Results: The UV-Vis absorption spectra of P3HT films showed a strong absorption peak at around 550 nm, which corresponds to the π-π* transition of the conjugated backbone. The absorption anisotropy was found to be , indicating a weak orientational ordering of the polymer chains in the film plane. The steady-state fluorescence anisotropy of P3HT films was measured with excitation and observation polarizations parallel and perpendicular to the film plane. The anisotropy was found to be , which is larger than the absorption anisotropy, indicating that the fluorescence emission has a higher degree of orientation than the absorption. The fluorescence decay of P3HT films was fitted to a bi-exponential function with a fast decay component (τ1) of ns and a slow decay component (τ2) of ns. The excited-state anisotropy of P3HT films was measured by using picosecond time-resolved fluorescence up-conversion technique. The excited-state anisotropy was found to be , which is larger than the steady-state anisotropy and absorption anisotropy, indicating that the excited-state molecules have a higher degree of orientation. Discussion: The weak absorption anisotropy of P3HT films is due to the random orientation of the polymer chains in the film plane. The larger steady-state fluorescence anisotropy compared to the absorption anisotropy is due to the selective fluorescence emission from orientationally ordered chains and the interchain interactions. The fast and slow decay components of the fluorescence decay are attributed to the exciton dissociation and recombination processes, respectively. The excited-state anisotropy is influenced by the excited-state dynamics of the polymer chains and the interchain interactions. The higher excited-state anisotropy compared to the steady-state anisotropy is due to the fast and efficient exciton dissociation process which leads to a higher degree of orientation of the excited-state molecules. Conclusion: In this paper, we have studied the steady-state and picosecond transient anisotropy of P3HT films. The result showed a weak absorption anisotropy and a higher fluorescence anisotropy, indicating that the orientation of the polymer chains in the film plane plays an important role in the optical properties. The excited-state anisotropy is larger than the steady-state anisotropy due to the fast and efficient exciton dissociation process. Our study provides a better understanding of the correlation between the structural anisotropy and the optical properties of P3HT films, which is useful for the design and optimization of optoelectronic devices made of P3HT.
