Jiang Hongji, Wang Zhong, Mao Bing, Bing Yan, Sun Ning, Yuan Jie
State Key Laboratory of Organic Electronics and Information Displays (Nanjing University of Posts and Telecommunications), Nanjing 210023, China; State Key Laboratory of Molecular Engineering of Polymers (Fudan University), Shanghai 200438, China; State Key Laboratory of Luminescent Materials and Devices (South China University of Technology), Guangzhou 510641, China.
State Key Laboratory of Organic Electronics and Information Displays (Nanjing University of Posts and Telecommunications), Nanjing 210023, China.
Spectrochim Acta A Mol Biomol Spectrosc. 2025 Jan 15;325:125147. doi: 10.1016/j.saa.2024.125147. Epub 2024 Sep 15.
To investigate the effects of steric hindrance fluorene and heavy-atom bromine on the general optoelectronic properties of star-shaped organic emitters based on 9-(2-cyanophenyl) carbazole (OCzPhCN) frameworks, heavy element of bromine and steric hindrance fluorene were introduced into OCzPhCN to produce four derivatives of 2-(3-bromo-9H-carbazol-9-yl)benzonitrile (BrCzPhCN), 2-(3-bromo-6-(9-(4-ethoxyphenyl)-9H-fluoren-9-yl)-9H-carbazol-9-yl)benzonitrile (BrFCzPhCN), 2-(3-(9-(4-ethoxyphenyl)-9H-fluoren-9-yl)-9H-carbazol-9-yl)benzonitrile (FCzPhCN) and 2-(3,6-bis(9-(4-ethoxyphenyl)-9H-fluoren-9-yl)-9H-carbazol-9-yl)benzonitrile (2FCzPhCN). The fluorene units obviously improve the thermal stability of the obtained compounds, and 2FCzPhCN has the highest thermal stability with 5 % mass heat loss temperature reaching 447 °C. In different polar solvents, the absorption peaks wavelength of OCzPhCN, FCzPhCN and 2FCzPhCN are basically unchanged, and the redshifted emission peaks are positively correlated with solvent polarity. The photoluminescence quantum yields (PLQYs) of OCzPhCN, BrCzPhCN, FCzPhCN, BrFCzPhCN and 2FCzPhCN powders were 20.17 %, 5.43 %, 30.75 %, 3.27 % and 23.56 %. The fluorescence and phosphorescent quantum efficiencies of OCzPhCN, BrCzPhCN, FCzPhCN, BrFCzPhCN and 2FCzPhCN powders are 9.76 % and 10.41 %, 1.2 % and 3.23 %, 28.45 % and 2.3 %, 3.27 % and 0 %, 23.56 % and 0 %. OCzPhCN, BrCzPhCN and FCzPhCN powders show obvious room temperature phosphorescent emission, and the phosphorescent emission lifetime of OCzPhCN, BrCzPhCN and FCzPhCN powders at 561 nm, 576 nm and 568 nm are 193.17 ms, 18.65 ms and 7.25 ms. Compared with OCzPhCN, the introduction of bromine decreases the PLQY and the phosphorescent lifetime of BrCzPhCN powder, while the fluorescence quantum efficiency of the compound FCzPhCN powder has been improved. The corresponding single-triplet energy splitting (ΔE) of OCzPhCN, FCzPhCN and 2FCzPhCN in solutions are 0.49 eV, 0.63 eV and 0.63 eV, and the corresponding ΔE values of OCzPhCN, BrCzPhCN FCzPhCN powders are 1.19 eV, 0.74 eV and 0.55 eV. The steric hindrance fluorene units result in smaller and stabilized ΔE in the solid powder states, and the same situation is opposite in the unimolecular solutions. The maximum external quantum efficiency of organic light-emitting diode based on 10,10'-(4,4'-sulfonylbis (4,1-phenylene)) bis (9,9-dimethyl-9,10-dihydroacridine) hosted by OCzPhCN reaches 12.7 %, and the external quantum efficiency at 100 cd/m rolls down to 11 %. OCzPhCN is the best emitters in terms of room temperature phosphorescent emission and host applications.
为研究空间位阻芴和重原子溴对基于9-(2-氰基苯基)咔唑(OCzPhCN)骨架的星形有机发光体一般光电性能的影响，将重元素溴和空间位阻芴引入OCzPhCN中，制备了2-(3-溴-9H-咔唑-9-基)苯甲腈(BrCzPhCN)、2-(3-溴-6-(9-(4-乙氧基苯基)-9H-芴-9-基)-9H-咔唑-9-基)苯甲腈(BrFCzPhCN)、2-(3-(9-(4-乙氧基苯基)-9H-芴-9-基)-9H-咔唑-9-基)苯甲腈(FCzPhCN)和2-(3,6-双(9-(4-乙氧基苯基)-9H-芴-9-基)-9H-咔唑-9-基)苯甲腈(2FCzPhCN)四种衍生物。芴单元明显提高了所得化合物的热稳定性，2FCzPhCN具有最高的热稳定性，5%质量热损失温度达到447℃。在不同极性溶剂中，OCzPhCN、FCzPhCN和2FCzPhCN的吸收峰波长基本不变，发射峰红移与溶剂极性呈正相关。OCzPhCN、BrCzPhCN、FCzPhCN、BrFCzPhCN和2FCzPhCN粉末的光致发光量子产率(PLQYs)分别为20.17%、5.43%、30.75%、3.27%和23.56%。OCzPhCN、BrCzPhCN、FCzPhCN、BrFCzPhCN和2FCzPhCN粉末的荧光和磷光量子效率分别为9.76%和10.41%、1.2%和3.23%、28.45%和2.3%、3.27%和0%、23.56%和0%。OCzPhCN、BrCzPhCN和FCzPhCN粉末表现出明显的室温磷光发射，OCzPhCN、BrCzPhCN和FCzPhCN粉末在561nm、576nm和568nm处的磷光发射寿命分别为193.17ms、18.65ms和7.25ms。与OCzPhCN相比，溴的引入降低了BrCzPhCN粉末的PLQY和磷光寿命，而化合物FCzPhCN粉末的荧光量子效率得到了提高。OCzPhCN、FCzPhCN和2FCzPhCN在溶液中的相应单重态-三重态能量分裂(ΔE)分别为0.49eV、0.63eV和0.63eV，OCzPhCN、BrCzPhCN、FCzPhCN粉末的相应ΔE值分别为1.19eV、0.74eV和0.55eV。空间位阻芴单元在固体粉末状态下导致更小且更稳定的ΔE，而在单分子溶液中情况相反。基于OCzPhCN主体的10,10'-(4,4'-磺酰基双(4,1-亚苯基))双(9,9-二甲基-9,10-二氢吖啶)的有机发光二极管的最大外量子效率达到12.7%，在100cd/m²时外量子效率降至11%。就室温磷光发射和主体应用而言，OCzPhCN是最佳发光体。
