一类窄带隙芴基共聚物的合成及其在发光二极管和太阳电池中的应用

基于9,9-二辛基芴(DOF)与窄带隙单体2,3-二甲基-5,8-二噻吩-喹喔啉(DDQ),通过Suzuki偶合反应,合成了一系列无规和交替窄带隙的芴基共聚物(PFO-DDQ),并对它们的紫外-可见吸收光谱、光致发光光谱、电致发光性能和光伏性能进行了初步研究.共聚物在380 nm和490 nm处有两处明显的吸收峰,其中490nm处的吸收强度随着共聚物中窄带隙单元(DDQ)含量的增加而成比例加强.随着共聚物中窄带隙单元(DDQ)含量的增加,电致发光峰值从580 nm红移到了635 nm.基于该类材料的橙红或饱和红色发光二极管最大外量子效率为1.33%,流明效率为1.54 Cd/A.试验中观察到了窄带隙单元的能量陷阱机制.以窄带隙单元含量为30%的聚合物(PFO-DDQ30)为电子给体、PCBM为电子受体所制备的共混体相异质结太阳电池最大能量转换效率为1.18%,开路电压0.9 V,短路电流密度2.66 mA/cm2.光敏曲线覆盖300 nm~700 nm.

FLUORENE-BASED COPOLYMERS FOR RED LIGHT-EMITTING DIODES AND BULK HETEROJUNCTION PHOTOVOLTAIC CELL

A series of low band-gap conjugated copolymers(PFO-DDQ) derived from 9,9-dioctylfluorene(DOF) and 2,3-dimethyl-5,8-dithien-2-yl-quinoxalines(DDQ) is prepared by the palladium-catalyzed Suzuki coupling reaction with the molar feed ratio of DDQ around 1%,5%,15%,30% and 50%.The obtained polymers are readily soluble in common organic solvents.The solutions and the thin solid films of the copolymers absorb light from 300～590 nm with two absorbance peaks at around 380 nm and 490 nm.The PL emission consists exclusively of DDQ unit emission at around 591～643 nm depending on the DDQ content in solid film.The EL emission peaks are red-shifted from 580 nm for PFO-DDQ1 to 635 nm for PFO-DDQ50.Efficient energy transfer due to exciton trapping on narrow-band-gap DDQ sites has been observed.The highest external quantum efficiency achieved with the device configuration ITO/PEDOT/PVK/PFO-DDQ15/Ba/Al is 1.33% with luminous efficiency 1.54 cd/A.Bulk heterojunction photovoltaic cells fabricated from composite films of PFO-DDQ30 copolymer and -phenyl C_61 butyric acid methyl ester(PCBM) as electron donor and electron acceptor,respectively in device configuration: ITO/PEDOT∶PSS/PFO-DDQ30∶PCBM/PFPNBr/Al shows power conversion efficiencies 1.18% with open-circuit voltage(V_oc) of 0.90 V and short-circuit current density(J_sc) of 2.66 mA/cm2 under AM 1.5 solar simulator(100 mW/cm2).The photocurrent response wavelengths of the PVCs based on PFO-DDQ30/PCBM blends covers 300～700 nm.This indicates that these kinds of low band-gap polymers are promising candidate for polymeric solar cells and red light-emitting diodes.