Highly efficient red electroluminescent polymers with dopant/host system and molecular dispersion feature: polyfluorene as the host and 2,1,3-benzothiadiazole derivatives as the red dopant
作者:Jun Liu、Lei Chen、Shiyang Shao、Zhiyuan Xie、Yanxiang Cheng、Yanhou Geng、Lixiang Wang、Xiabin Jing、Fosong Wang
DOI:10.1039/b712562c
日期:——
By selecting polyfluorene as the polymer host, choosing 2,1,3-benzothiadiazole derivative moieties as the red dopant units and covalently attaching 0.3 mol% of the dopant units to the side chain of the polymer host, we developed a novel series of red electroluminescent polymers of dopant/host system with molecular dispersion feature. Their EL spectra exhibited predominant red emission from the dopant units because of the energy transfer and charge trapping from the polymer backbone to the dopant units. The emission wavelength of the polymers could be tuned by modifying the chemical structures of the dopant units. Single-layer devices (device configuration: ITO/PEDOT : PSS/polymer/Ca/Al) of these polymers emitted red light with a peak at 615 nm, a luminous efficiency of 5.04 cd A−1 and an external quantum efficiency of 3.47%, or emitted deep-red light with a peak at 650 nm, a luminous efficiency of 1.70 cd A−1 and an external quantum efficiency of 2.75%. Their high EL efficiencies were due to the energy transfer and charge trapping from the host to the dopant units as well as the molecular dispersion of the dopant units in the host. Increase of the dopant unit content led to increased turn-on voltages and decreased EL efficiencies of the resulting devices.
通过选择聚氟烯作为聚合物宿主,选择2,1,3-苯并噻二唑衍生物作为红色掺杂单元,并将0.3 mol%的掺杂单元共价连接到聚合物宿主的侧链上,我们开发了一系列具有分子分散特性的红色电致发光掺杂/宿主体系聚合物。它们的电致发光光谱显示,掺杂单元产生的红色发光主要是由于聚合物主链向掺杂单元的能量转移和电荷捕获。通过修改掺杂单元的化学结构,可以调节这些聚合物的发射波长。这些聚合物的单层器件(器件结构:ITO/PEDOT:PSS/聚合物/Ca/Al)发出了峰值为615nm的红光,光效为5.04 cd A−1,外部量子效率为3.47%;或者发出了峰值为650nm的深红光,光效为1.70 cd A−1,外部量子效率为2.75%。它们的高电致发光效率归因于宿主到掺杂单元的能量转移和电荷捕获,以及掺杂单元在宿主中的分子分散。掺杂单元含量的增加导致开启电压上升和器件电致发光效率下降。