Conjugated polymers with p‐orbital overlap show intramolecular‐conformation‐dependent photophysical and electrical properties. Compared to the non‐planar segments, the planar conformation segments have a relatively long effective conjugated length and rigid backbone structure, which are beneficial for the enhancement of optoelectronic properties. Herein, the effect of film thickness on the formation capacity of planar (β) conformations in polyfluorene (poly[4‐(octyloxy)‐9,9‐diphenylfluorene‐2,7‐diyl]‐co‐[5‐(octyloxy)‐9,9‐diphenylfluorene‐2,7‐diyl], PODPF) for the fabrication of stable deep‐blue polymer light‐emitting diodes (PLEDs) is explored. Thickness‐tunable films with thicknesses ranging from 15 to 270 nm by controlling the concentration of precursor solution are prepared. The main observations are as follows. The PODPF chains in thin films are less likely to adopt the β conformations associated with the loose interchain packing in nano‐aggregates than those in thick films. Red‐shifted and well‐resolved emission spectra are observed for the annealed film with a high thickness, indicating the greater presence of β‐conformation segments. More interestingly, interchain aggregation is a necessary but not sufficient condition for the formation of β conformations. Finally, PLEDs based on β‐conformation segments have outstanding brightness, low turn‐on voltage, and stable deep‐blue electroluminescent behavior, confirming the unique advantage of planar conformation for optoelectronic applications.

中文翻译：

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聚二芳基芴中平面（β）构象的厚度依赖性形成能力和机制，用于稳定的深蓝色聚合物发光二极管


具有 p 轨道重叠的共轭聚合物表现出分子内构象依赖的光物理和电学特性。与非平面构象片段相比，平面构象片段具有相对较长的有效共轭长度和刚性的骨架结构，有利于光电性能的增强。在此，膜厚度对聚芴（聚[4-（辛氧基）-9,9-二苯基芴-2,7-二基]-co-[5-（辛氧基）-）中平面（β）构象形成能力的影响9,9-二苯基芴-2,7-二基]，PODPF）用于制造稳定的深蓝色聚合物发光二极管（PLED）。通过控制前驱体溶液的浓度，制备了厚度范围为15至270 nm的厚度可调薄膜。主要观察结果如下。与厚膜中的 PODPF 链相比，薄膜中的 PODPF 链不太可能采用与纳米聚集体中松散链间堆积相关的 β 构象。对于高厚度的退火薄膜，观察到红移且分辨率良好的发射光谱，表明存在更多的 β 构象片段。更有趣的是，链间聚集是β构象形成的必要但非充分条件。最后，基于β构象片段的PLED具有出色的亮度、低开启电压和稳定的深蓝色电致发光行为，证实了平面构象在光电应用中的独特优势。