Developing high-efficiency blue thermally activated delayed fluorescence (TADF) emitters is still a formidable challenge. Here, we report five blue TADF emitters designed by simply changing the frequently used methyl group (C1) to a longer one gradually to subtly adjust the energy levels. DAc-C1–DAc-C5 are developed by using diphenylsulfone (DPS) as the acceptor and acridine with different-length alkyl chains on C(9) as the donor groups. These five compounds have high photoluminescence quantum yields (PLQYs) (75%–84%) with blue emission. The DAc-C2-based OLED device exhibits the maximum external quantum efficiency (EQE) of up to 24.1% with CIE (0.15, 0.19), which is 1.42 times higher than that of state-of-the-art TADF OLEDs based on DAc-C1 (EQE: 17.0%) under the same conditions, confirming the power of the molecular design strategy. Furthermore, the crystal analyses partially explain the influence of the alkyl chain on the device property, demonstrating a new approach for achieving TADF luminogens with high performance.

开发高效的蓝色热激活延迟荧光（TADF）发射器仍然是一个艰巨的挑战。在这里，我们报告了五个蓝色TADF发射器，这些发射器是通过简单地将常用的甲基（C1）逐渐更改为更长的甲基以巧妙地调节能级而设计的。DAc-C1-DAc-C5是通过使用二苯砜（DPS）作为受体和在C（9）上具有不同长度烷基链的a啶作为供体基团而开发的。这五个化合物具有很高的光致发光量子产率（PLQYs）（75％–84％），并且具有蓝色发射。基于DAc-C2的OLED器件在CIE（0.15，0.19）的情况下具有高达24.1％的最大外部量子效率（EQE），这是基于DAc的最新TADF OLED的1.42倍-C1（EQE：17.0％）在相同条件下，证实了分子设计策略的强大功能。此外，