【作者】 杨涛；

【导师】 赵祖金；

【作者基本信息】 华南理工大学 ， 材料科学与工程， 2024， 硕士

【摘要】 有机发光二极管（OLED）具有优异的色彩表现、高对比度、快速响应时间和柔性等特点而被广泛应用于各类显示面板中。随着近三十五年的发展,OLED中的发光材料也在不断地被改进。其中,纯有机小分子热活化延迟荧光（TADF）材料不仅拥有较低的成本且能够高效地通过反向系间窜越（RISC）过程捕获三线态激子,从而实现较高的电致发光（EL）效率。折叠构型分子具有较大扭转角,能够使最高分子占据轨道（HOMO）与最低分子未占据轨道（LUMO）充分分离以取得较小的最低激发单线态（S₁）与最低激发三线态（T₁）能级差(ΔE_ST)。此外,分子内空间电荷转移（TSCT）的存在也能够保证这类分子兼具较高的绝对荧光量子产率(Φ_PL)。因此本论文围绕3,6-二叔丁基咔唑为桥联基团构筑了一系列的折叠构型分子,并系统地研究了它们的光物理性质、构效关系以及在OLED中的应用。具体内容包括以下三章内容:第二章以平面性较好的呫吨酮为受体单元,9-苯基咔唑及其衍生物为给体单元设计合成了三个折叠构型分子tCz-XT-BCz、tCz-XT-3Cz和tCz-XT-ICz。理论计算证明这三个分子均存在分子内的弱相互作用。实验证明了tCz-XT-BCz、tCz-XT-3Cz具有TADF性质且延迟寿命较短,分别为2.1μs和3.1μs。实验结果显示tCz-XT-ICz没有明显的延迟寿命组分,但经自旋轨道耦合（SOC）矩阵分析证明了其发光过程可能存在高能级的反向系间窜越（hRISC）。EL性能表征显示这一系列分子能够实现高效的具有较低滚降的蓝光及深蓝光OLED器件。第三章以第二章中π-π相互作用区域更大的tCz-XT-3Cz和tCz-XT-ICz为基础,增加给体数量设计并合成了tCz-3Cz-XT-3Cz和tCz-ICz-XT-ICz两个分子,探究三明治折叠构型空间共轭分子的发光性质及其光电性能。实验结果和理论计算显示三明治折叠构型具有比普通折叠构型更强的分子内弱相互作用,其π-π相互作用区域更宽。实验与理论计算证明了这两个分子可能具有hRISC性质。tCz-3Cz-XT-3Cz的发光由TSCT主导,而tCz-ICz-XT-ICz的发光主要是以价键电荷转移（TBCT）占主导且HOMO与LUMO较彻底的分离而使得其Φ_PL较低。第四章以更大的准平面基团5,9-二氧杂-13b-硼萘并[3,2,1-de]蒽（BO）为受体片段,利用吡啶基团来调控9-苯基咔唑给体的平面性与给电子能力,探究给体平面性的提高对于折叠构型分子发光的影响。实验证明经吡啶修饰的tCz-BO-PCz在掺杂薄膜和器件中的光谱具有更窄的半峰宽（FWHM）并实现了近紫外发射。实验证明tCz-BO-BCz和tCz-BO-PCz具有较大的ΔE_ST。理论计算表明这两个分子的发光过程存在hRISC。更多还原

【Abstract】 Organic light emitting diodes（OLEDs）are widely used in various display panels due to their excellent color performance,high contrast,fast response time,and flexibility.With the development of nearly 35 years,luminescent materials in OLEDs are also constantly being improved.Among them,purely organic small molecule thermally activated delayed fluorescence（TADF）materials not only have lower costs but also can efficiently capture triplet excitons through reverse intersystem crossing（RISC）processes,thereby achieving higher electroluminescence（EL）efficiency.Folded molecules with intramolecular through-space charge transfer（TSCT）property are such a type of molecules having a large twist angle to efficiently separate the highest occupied molecular orbit（HOMO）and the lowest unoccupied molecular orbit（LUMO）to yield a smaller energy splitting(ΔE_ST)between the lowest excited singlet（S₁）and the lowest excited triplet（T₁）.Moreover,folded molecules have high absolute fluorescence quantum yield(Φ_PL)due to the presence of through-space conjugation.Therefore,this paper constructs a series of folded molecules utilizing 3,6-di-tert-butylcarbazole as a bridging group,and systematically studies their photophysical properties,structure-property relationships,and applications in OLED.The specific content includes the following three chapters:In Chapter 2,tCz-XT-BCz,tCz-XT-3Cz,and tCz-XT-ICz were designed and synthesized using xanthone as the acceptor unit and 9-phenylcarbazole and its derivatives as the donor unit.Theoretical calculations have shown that all three molecules exhibit weak intramolecular interactions.The experiment proved that tCz-XT-BCz and tCz-XT-3Cz have TADF properties with short delay lifetimes,with values of 2.1 and 3.1μs,respectively,while tCz-XT-ICz does not have a significant delayed lifetime component.Spin orbit coupling（SOC）matrix analysis has shown that luminescence process of tCz-XT-ICz may possess high-level reverse intersystem crossing（hRISC）.EL performance characterization shows that this series of molecules can efficiently achieve blue and deep-blue OLED devices with low roll-off.In Chapter 3,based on the largerπ-πinteraction regions of tCz-XT-3Cz and tCz-XT-ICz mentioned in Chapter 2,tCz-3Cz-XT-3Cz and tCz-ICz-XT-ICz were designed and synthesized by increasing the number of donors.The photophysical and optoelectronic properties of the sandwich-folded molecules were investigated.The experimental results and theoretical calculations show that the sandwich-folded configuration has stronger intramolecular weak interactions than the ordinary folded configuration,and itsπ-πinteraction region is wider.Moreover,experimental and theoretical calculations have demonstrated that these two molecules may possess hRISC properties.The photophysical properties of tCz-3Cz-XT-3Cz is dominated by TSCT,while the photophysical properties of tCz-ICz-XT-ICz is mainly dominated by through-bond charge transfer（TBCT）,and the separation of HOMO and LUMO is relatively thorough,resulting inΦ_PL is relatively low.In Chapter 4,a quasi-planar group 5,9-dioxa-13b-boronaphthalo[3,2,1-de]anthracene（BO）was used as the acceptor fragment,and the pyridine group was used to regulate the planarity and electron donating ability of 9-phenyl-carbazole donors,exploring the effect of increased donor planarity on the luminescence of folded molecules.Experimental results have shown that pyridine modified tCz-BO-PCz exhibits a narrower full width at half maxima（FWHM）both in doped thin films and devices,achieving pure near-ultraviolet emission.Moreover,tCz-BO-BCz and tCz-BO-PCz have significantΔE_ST.Theoretical calculations indicate the presence of hRISC in the luminescence process of these two molecules.更多还原