Yang Yike, Li Kuofei, Wang Chenxu, Zhan Hongmei, Cheng Yanxiang
State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun, 130022, P.R. China.
University of Chinese Academy of Sciences, Beijing, 100049, P.R. China.
Chem Asian J. 2019 Feb 15;14(4):574-581. doi: 10.1002/asia.201801813. Epub 2019 Jan 29.
Three sets of conjugated polymers with backbone-donor/pendant-acceptor architectures, named PCzA3PyB, PCzAB2Py, and PCzAB3Py, are designed and synthesized. The three isomeric benzoylpyridine-based pendant acceptor groups are 6-benzoylpyridin-3-yl (3PyB), 4-((pyridin-2-yl)carbonyl)phenyl (B2Py) and 4-((pyridin-3-yl)carbonyl)phenyl (B3Py), whereas the identical backbone consists of 3,6-carbazolyl and 2,7-acridinyl rings. One acridine ring and each acceptor group constitute a definite thermally activated delayed fluorescence (TADF) unit, incorporated into the main chain of the polymers through the 2,7-position of the acridine ring with the varied content. All of the polymers display legible TADF features with a short microsecond-scale delayed lifetime (0.56-1.62 μs) and a small singlet/triplet energy gap (0.10-0.19 eV). Progressively redshifted emissions are observed in the order PCzAB3Py, PCzA3PyB, and PCzAB2Py owing to the different substitution patterns of the pyridyl group. Photoluminescence quantum yields can be improved by regulating the molar content of the TADF unit in the range 0.5-50 %. The non-doped organic light-emitting devices (OLEDs) fabricated by solution-processing technology emit yellow-green to orange light. The polymers with 5 mol % of the TADF unit exhibit excellent comprehensive electroluminescence performance, in which PCzAB2Py5 achieves a maximum external quantum efficiency (EQE) of 11.9 %, low turn-on voltage of 3.0 V, yellow emission with a wavelength of 573 nm and slow roll-off with EQE of 11.6 % at a luminance of 1000 cd m and driving voltage of 5.5 V.
设计并合成了三种具有主链供体/侧链受体结构的共轭聚合物，分别命名为PCzA3PyB、PCzAB2Py和PCzAB3Py。三种基于苯甲酰吡啶的异构侧链受体基团分别为6-苯甲酰吡啶-3-基（3PyB）、4-（（吡啶-2-基）羰基）苯基（B2Py）和4-（（吡啶-3-基）羰基）苯基（B3Py），而相同的主链由3,6-咔唑基和2,7-吖啶基环组成。一个吖啶环和每个受体基团构成一个确定的热激活延迟荧光（TADF）单元，通过吖啶环的2,7位以不同含量并入聚合物主链。所有聚合物均表现出清晰的TADF特征，具有短至微秒级的延迟寿命（0.56 - 1.62 μs）和小的单线态/三线态能隙（0.10 - 0.19 eV）。由于吡啶基的不同取代模式，按PCzAB3Py、PCzA3PyB和PCzAB2Py的顺序观察到发射光谱逐渐红移。通过在0.5 - 50%范围内调节TADF单元的摩尔含量，可以提高光致发光量子产率。采用溶液处理技术制备的非掺杂有机发光二极管（OLED）发出黄绿色至橙色光。含有5 mol% TADF单元的聚合物表现出优异的综合电致发光性能，其中PCzAB2Py5实现了11.9%的最大外量子效率（EQE）、3.0 V的低开启电压、573 nm波长的黄色发射以及在1000 cd m亮度和5.5 V驱动电压下EQE为11.6%时的缓慢滚降。
