Optoelectronic properties of fluorene-co-4,7-difuran-2,1,3-benzothiadiazole copolymers

摘要

Light-emitting and photovoltaic properties of copolymers (PFO-FBT) based on 9,9-dioctylfluorene and 4,7-difuran-2,1,3-benzothiadiazole (FBT) units were investigated. The copolymers show two absorbance peaks at around 382 nm and 530 nm, respectively. The relative absorbance at around 530 nm of the PFO-FBT copolymers increases with the increasing FBT content. The EL emissions are red-shifted from 611 nm to 702 nm by increasing the FBT content in the copolymer. The highest EL external quantum efficiency achieved with the device configuration of ITO/PEDOT/PVK/PFO-FBT0.1/Ba/Al is 2.32% with the luminance of 441.3 cd/m(2) at a current density of 33 mA/cm(2). Efficient energy transfer due to exciton trapping on low band-gap FBT sites was observed. The bulk-heterojunction photovoltaic cell used PFO-FBT50 copolymer as the electron donor and methanofullerene [6,6]-phenyl C61-butyric acid methyl ester (PCBM) as the electron acceptor shows an energy conversion efficiency of 1.13% with open-circuit voltage (V(oc)) of 0.85 V and short-circuit current density (J(sc)) of 3.39 mA/cm(2) under AM 1.5 solar simulator (100 mW/cm(2)), and the edge of the spectral photoresponse is at similar to 750 nm.