A series of alkali metal salts doped pluronic block copolymer F127 were used as electron injection/transport layers (ETLs) for polymer light-emitting diodes with poly[2-(4-(3′,7′-dimethyloctyloxy)-phenyl)-p-phenylenevinylene] (P-PPV) as the emission layer. It was found that the electron transport capability of F127 can be effectively enhanced by doping with alkali metal salts. By using Li2CO3 (15%) doped F127 as ETL, the resulting device exhibited improved performance with a maximum luminous efficiency (LE) of 13.59 cd/A and a maximum brightness of 5529 cd/m2, while the device with undoped F127 as ETL only showed a maximum LE of 8.78 cd/A and a maximum brightness of 2952 cd/m2. The effects of the doping concentration, cations and anions of the alkali metal salts on the performance of the resulting devices were investigated. It was found that most of the alkali metal salt dopants can dramatically enhance the electron transport capability of F127 ETL and the performance of the resulting devices was greatly improved.
The Institute of Polymer Optoelectronic Materials & Devices, South China University of Technology, Guangzhou, in close collaboration with the Department of Electrical and Electronic Engineering, The University of Hong Kong, has shown that the band gap and
Three two-dimensional like conjugated copolymers PFSDCN,PFSDTA and PFSDCNIO,which consist of alternating fluorene and triphenylamine main chain,and different pendant acceptor groups (malononitrile,1,3-diethtyl-2-thiobarbituric acid and 2-(1,2-dihydro-1-oxoinden-3-ylidene)malononitrile) with thiophene as π-bridge,have been designed,synthesized and characterized.The structure-property relationships of the two-dimensional like conjugated copolymers were systematically investigated.The absorption spectra,band gaps,and energy levels of the polymers were effectively tuned by simply attaching different acceptor groups.As the electron-withdrawing ability of the acceptors increased,the band gaps of the polymers were narrowed from 2.05 to 1.61 eV;meanwhile,the LUMO energy levels of the polymers decreased from -3.27 to -3.75 eV,whereas their relatively deep HOMO energy levels of ～-5.35 eV were preserved.BHJ solar cells were fabricated and characterized by using the three polymers as donor materials and the highest power conversion efficiency of 2.87% was achieved for the device based on PFSDTA:(6,6)-phenyl-C71-butyric acid methyl ester blend.
