A directional crystallization of the compound 2,7-dioctyl[1]benzothieno[3,2-b][1]benzothiophene (C8-BTBT-C8) based on a temperature gradient approach has been used as a post-deposition process to control the crystalline morphology of thin films. C8-BTBT-C8 films of arbitrary thicknesses have been fabricated by spin-coating and subjected to the directional crystallization process. Dewetting is prevented by the liquid crystal phase of C8-BTBT-C8, allowing the formation of flat and rather uniform thin films with large crystalline domains. Spin-coating concentration, gradient magnitude, and cooling rate have been varied to explore a large set of crystallization conditions and to correlate them with the thin film morphology. The latter has been characterized by a combined use of optical profilometry, polarized optical microscopy, X-ray reflectometry, and X-ray diffraction measurements. The characterization results confirm that the roughness and crystalline order of the thin films are improved after the temperature gradient treatments: (1) high cooling rate treatments (≥9 °C min⁻¹) significantly reduce the roughness of high thickness films, leading to good continuity and uniformity of the films; (2) dendritic growth dominates not only the films with low thickness but also films with high thickness treated at low cooling rates (<9 °C min⁻¹); (3) the out-of-plane order and the in-plane alignment of the crystallites are also remarkably enhanced by the temperature gradient treatments.

中文翻译：

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C8-BTBT-C8薄膜在温度梯度下的定向结晶

化合物2,7-二辛基[1]苯并噻吩并[3,2- b ]的定向结晶基于温度梯度方法的] [1]苯并噻吩（C8-BTBT-C8）已用作沉积后过程，以控制薄膜的晶体形态。通过旋涂已经制备了任意厚度的C8-BTBT-C8膜，并进行了定向结晶过程。C8-BTBT-C8的液晶相可防止去湿，从而形成具有大晶畴的平坦且相当均匀的薄膜。旋涂浓度，梯度量和冷却速率已经改变，以探索大量的结晶条件并将它们与薄膜形态相关联。后者的特征在于结合使用光学轮廓仪，偏振光学显微镜，X射线反射仪和X射线衍射测量。^-1）显着降低高厚度薄膜的粗糙度，从而使薄膜具有良好的连续性和均匀性；（2）在低冷却速率（＜9℃min ^-1）下处理的不仅高厚度的薄膜而且高厚度的薄膜均以树枝状生长为主；（3）通过温度梯度处理，微晶的面外排列和面内取向也显着增强。