Given that optoelectronic devices are the solid-state application of associated materials and considering that rationally functionalized pyridines are emerging as promising hole transport materials (HTMs) for optoelectronic devices, the present work reports in-depth insights through detailed experimental and theoretical studies on how the peripheral substituents of a pyridine core may affect various properties of HTMs for organic light-emitting diodes. In this regard, four compounds, P₃C₀Py, P₂C₁Py, P₁C₂Py, and P₀C₃Py, have been synthesized for the current study where the number of peripheral carbazole units was systematically varied to study the change in molecular arrangements in the solid state. Such strategic functionalization led to a reduction in hole reorganization energy, which may further lead to significant enhancement in hole transport properties. The high triplet energy of these molecules might reduce the exciton quenching at the interface of the hole injection layer (HIL) and the emissive layer (EML). The theortically calculated charge transfer excited singlet state at a higher oscillator strength indicated the charge transfer characteristics of these molecules. Similarly, the theortical low hole and exciton binding energies indicated that the current materials may show high hole transportability. The single crystal analysis revealed how molecular arrangement varies from zig-zag to wavelike patterns with a change in the number of peripheral carbazole units around the pyridine core. Finally, the hole-only device with P₀C₃Py indicated good hole-transporting characteristics of these molecules, even at lower voltages; hence, they can be used as efficient HTMs in organic light-emitting diodes (OLEDs).

中文翻译：

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吡啶核心周围的外围功能对分子排列的影响：潜在的空穴传输材料

鉴于光电器件是相关材料的固态应用，并考虑到合理功能化的吡啶正在成为光电器件有前途的空穴传输材料（HTM），本工作通过详细的实验和理论研究报告了关于如何吡啶核的外围取代基可能会影响有机发光二极管 HTM 的各种性能。在这方面，本研究合成了四种化合物： P ₃ C ₀ Py、P ₂ C ₁ Py、P ₁ C ₂ Py和P ₀ C ₃ Py ，其中外围咔唑单元的数量系统地变化为研究固态中分子排列的变化。这种策略性功能化导致空穴重组能降低，这可能进一步导致空穴传输性能的显着增强。这些分子的高三线态能量可能会减少空穴注入层（HIL）和发射层（EML）界面处的激子猝灭。理论上计算的较高振荡强度下的电荷转移激发单线态表明了这些分子的电荷转移特性。类似地，理论上的低空穴和激子结合能表明当前材料可能表现出高空穴传输性。单晶分析揭示了分子排列如何随着吡啶核心周围的外围咔唑单元数量的变化而从锯齿形到波浪形图案变化。最后，具有P ₀ C ₃ Py的纯空穴器件表明这些分子即使在较低电压下也具有良好的空穴传输特性。因此，它们可以用作有机发光二极管（OLED）中的高效HTM。