随着热活化延迟荧光（TADF）材料的迅速发展，其在蓝色有机发光二极管（OLED）领域的应用日益受到关注。尽管已取得了显著的进展，但如何平衡高效率和高稳定性的挑战，仍然是蓝色TADF材料面临的主要问题。本论文通过采用π扩展策略，对少给体苯腈-咔唑类TADF材料及器件进行了研究，具体如下：1. 针对少给体苯腈-咔唑类TADF材料发光效率低下的问题，采用π扩展策略，在氰基对位引入苯基π扩展受体，实现了分子最低未占据分子轨道（LUMO）的分布离域，从而提高了分子的辐射跃迁速率。通过调节π扩展苯基上取代基，进一步调控了分子单三线态能级差（ΔEST），从而提高TADF发光效率。相较于未引入π扩展受体的分子，新材料的光致量子产率（PLQY）和反向系间窜越速率（kRISC）获得显著提升。其中2PCzBN-FPh的PLQY为96%，kRISC达到了5.63×105 s-1，较对比材料提升了一个数量级。以其为染料构建的蓝色OLED展现出25.1%的最大外量子效率和56.9 lm W-1的高功率效率，性能相较对比器件显著提升，实现了少给体苯腈-咔唑类TADF材料发光效率的突破。2. 采用具有多重共振（MR）性质的硼氧类受体基团DBA作为π扩展基团。与非MR受体基团对比，引入MR受体基团后PLQY显著提高，其中2tCzBN-CF3DBA分子表现出0.03 eV的极低ΔEST值和高达1.8×106 s-1的kRISC，在反向系间窜越速率上实现了突破。以该材料作为染料的器件展现出25.6%的高EQE，并在1000 cd m-2初始亮度下的T50寿命达到540小时，展现出优异的稳定性。该分子89.5%的水平跃迁偶极取向进一步证实了具有大平面结构的DBA基团对提升光取出效率的作用。3.引入吲哚并咔唑的稠环结构，将π扩展策略同时应用在苯腈-咔唑类TADF材料的给体和受体中，进一步使得最高占据分子轨道（HOMO）分布离域。以苯基为π扩展受体的2ICzBN-Ph和2ICzBN-FPh分子，kRISC提升至106 s-1。以其为染料制备的器件最大EQE均超过30%。以TDBA为π扩展受体的分子表现出0.07 eV的ΔEST和2.8×106 s-1的kRISC，以其为染料制备的器件实现了26.9%的最大EQE和1000 cd m-2初始亮度下320小时的T50寿命。上述结果证实了吲哚并咔唑基团对分子发光效率的促进作用。通过不同给受体的搭配，我们系统研究了π扩展策略对苯腈-咔唑类TADF材料发光性能的影响。

With the rapid development of Thermally Activated Delayed Fluorescence (TADF) materials, their application in the field of blue Organic Light Emitting Diodes (OLEDs) has increasingly garnered attention. Despite significant progress, balancing high efficiency with good stability remains a major challenge for blue TADF materials. This thesis explores a π-extension strategy for cyanobenzene-carbazole-based TADF materials and their devices as follows:1. To address the issue of low luminescence efficiency in less donor cyanobenzene-carbazole-based TADF materials with few donors, a π-extension strategy was employed by introducing a phenyl π-extension acceptor at para position of the cyano moiety. This realized the delocalization of the Lowest Unoccupied Molecular Orbital (LUMO) distribution, thereby enhancing the molecule‘s radiative transition rate. By adjusting the substituents on the π-extended phenyl group, we further regulated the singlet-triplet energy gap (ΔEST) to improve the TADF luminescence efficiency. Compared to molecules without π-extended acceptors, the new materials achieved significant improvements in Photoluminescence Quantum Yield (PLQY) and Reverse Intersystem Crossing rate (kRISC), Where 2PCzBN-FPh showed a PLQY of 96% and a kRISC of 5.63×105 s-1, an order of magnitude improvement over comparative materials. The blue OLEDs fabricated with this dye exhibited the highest External Quantum Efficiency (EQE) of 25.1% and a high power efficiency of 56.9 lm W-1, significantly improving upon comparator devices and marking a breakthrough in the luminescence efficiency of less donor cyanobenzene-carbazole-based TADF materials with few donors.2. A boron-oxygen type π-extension group DBA, with Multiple-Resonance (MR) properties, was used as the π-extension group. Compared to non-MR acceptor groups, the introduction of MR acceptor groups significantly improved the PLQY. The 2tCzBN-CF3DBA molecule demonstrated an extremely low ΔEST value of 0.03 eV and a high kRISC of 1.8×106 s-1, achieving a breakthrough in the Reverse Intersystem Crossing rate. Devices using this material as dye displayed a high EQE of 25.6% and an impressive T50 lifetime of 540 hours at an initial brightness of 1000 cd m-2, showing exceptional stability. The 89.5% horizontal transition dipole orientation further confirmed the DBA group‘s role in enhancing light extraction efficiency with its large planar structure.3. By introducing the fused ring structure of indolocarbazole, the π-extension strategy was applied to both donors and acceptors of cyanobenzene-carbazole-based TADF materials, further enabling delocalization of the highest occupied molecular orbital (HOMO). For molecules 2ICzBN-Ph and 2ICzBN-FPh with phenyl as a π-extension acceptor, the kRISC was elevated to 106 s-1. Devices fabricated with these dyes exceeded maximum EQEs exceeding 30%. Molecules based on TDBA π-extended acceptors displayed a ΔEST of 0.07 eV and a kRISC of 2.8×106 s-1, Devices fabricated with it achieved a maximum EQE of 26.9% and a T50 lifetime of 320 hours at an initial brightness of 1000 cd m-2. These results confirmed the promoting effect of indolocarbazole groups on molecular luminescence efficiency. By pairing different donors and acceptors, we systematically studied the impact of the π-extension strategy on the luminescence performance of cyanobenzene-carbazole-based TADF materials.