Green light-emitting polyfluorenes with improved color purity incorporated with 4,7-diphenyl-2,1,3-benzothiadiazole moieties
作者:Jun Liu、Laju Bu、Jinpeng Dong、Quanguo Zhou、Yanhou Geng、Dongge Ma、Lixiang Wang、Xiabin Jing、Fosong Wang
DOI:10.1039/b700004a
日期:——
By incorporating 4,7-diphenyl-2,1,3-benzothiadiazole instead of 2,1,3-benzothiadiazole into the backbone of polyfluorene, we developed a novel series of green light-emitting polymers with much improved color purity. Compared with the state-of-the-art green light-emitting polymer, poly(fluorene-co-benzothiadiazole) (λmax = 537 nm), the resulting polymers (λmax = 521 nm) showed 10–20 nm blueshifted electroluminescence (EL) spectra and greatly improved color purity because the insertion of two phenylene units between the 2,1,3-benzothiadiazole unit and the fluorene unit reduced the effective conjugation length in the vicinity of the 2,1,3-benzothiadiazole unit. As a result, the resulting polymers emitted pure green light with CIE coordinates of (0.29, 0.63), which are very close to (0.26, 0.65) of standard green emission demanded by the National Television System Committee (NTSC). Moreover, the insertion of the phenylene unit did not affect the photoluminescence (PL) and EL efficiencies of the resulting polymers. PL quantum efficiency in solid films up to 0.82 was demonstrated. Single-layer devices (ITO/PEDOT/polymer/Ca/Al) of these polymers exhibited a turn-on voltage of 4.2 V, luminous efficiency of 5.96 cd A−1 and power efficiency of 2.21 lm W−1. High EL efficiencies and good color purities made these polymers very promising for display applications.
通过在聚芴骨架中加入 4,7- 二苯基-2,1,3-苯并噻二唑而不是 2,1,3-苯并噻二唑,我们开发出了一系列新型绿色发光聚合物,其颜色纯度大大提高。与最先进的绿色发光聚合物聚(芴-共苯并噻二唑)(λmax = 537 nm)相比,所得到的聚合物(λmax = 521 nm)显示出 10-20 nm 的蓝移电致发光(EL)光谱,并且颜色纯度大大提高,这是因为在 2,1,3-苯并噻二唑之间插入了两个亚苯基单元、1,3-苯并噻二唑单元和芴单元之间插入了两个亚苯基单元,从而减少了 2,1,3-苯并噻二唑单元附近的有效共轭长度。因此,生成的聚合物发出的纯绿光的 CIE 坐标为(0.29, 0.63),非常接近美国国家电视系统委员会(NTSC)要求的标准绿光(0.26, 0.65)。此外,插入亚苯基单元并不影响所得聚合物的光致发光(PL)和电致发光效率。固体薄膜的 PL 量子效率高达 0.82。这些聚合物的单层器件(ITO/PEDOT/聚合物/Ca/Al)的开启电压为 4.2 V,发光效率为 5.96 cd A-1,功率效率为 2.21 lm W-1。较高的 EL 效率和良好的色纯度使这些聚合物在显示应用中大有可为。