摘要
利用不同比例的烷基芴 噻吩无规共聚物 ,制备了聚合物薄膜发光二极管 ,研究了不同噻吩含量对器件电致发射光谱的影响 ,发现改变共聚噻吩含量可有效调节器件发光谱色。通过研究器件在增加电流密度、升温老化处理后的光谱演变发现 ,相应器件的谱色稳定性在噻吩含量达到 5 %～ 10 %后相当稳定 ,噻吩含量10 %的共聚芴所制备的器件在电流密度达到 5 2 0mA/cm2 或经过高达 16 0℃温度老化后发光谱色无变化。初步探讨了共聚芴荧光谱色随噻吩含量变化的机制 ,认为无规共聚已使得两种共轭单元对应的能带结构发生相当程度的杂化。而对器件谱色随电流升高、温度老化表现出的优异稳定性 ,则认为源于低带隙材料的引入破坏了聚芴分子链的共平面结构 ,提高了形成激基缔合物的能垒。
Polymer film light emitting diodes based on dialkylfluorene thiophene copolymers with different thiophene content were made. The device structure was ITO/PEDOT:PSS/dialkylfluorene thiophene copolymer layer/Ba/Al. Typical turn on voltage was about 5V and the highest external quantum efficiency reached 1 8% and the highest current efficiency reached 12cd/A. It was found that the electroluminescent spectra of the LED based on this series of copolyfluorenes could be adjusted effectively by changing the content of the thiophene comonomer. By comparing the spectral variation of the devices along with the increase of the current density or after thermal annealing at different temperatures, it was found that the emission spectra were rather stable when the thiophene content reached 5～10%. For device based on the polydialkylfluorene co thiophene with 10% thiophene comonomer, no apparent spectral change was found even if the current density was as high as 520mA/cm 2 or after the devices were annealed at 160℃ for 2 hours on hotplate. Mechanism of the spectral adjustment with thiophene content was preliminarily discussed and it was believed that the energy level structures corresponding to the two kinds of conjugated chain segments were hybridized to a high extent. As to the excellent spectral stability of devices with current increasing or thermal annealing temperature, the origin was believed to be the introduction of low bandgap comonomer which had destructed the coplanar structure of polyfluorene main chain and thus increased the energy barrier to form excimer.
出处
《发光学报》
EI
CAS
CSCD
北大核心
2002年第5期431-434,共4页
Chinese Journal of Luminescence
基金
国家自然科学基金资助项目 (2 9992 5 3 0 6)
