The films of two x-shape oligo(thiophene)s,3,4-dibithienyl-2,5-dithienylthiophene (7T) and 2,5-dibithienyl-3,4ditrithienylthiophene (11T),which are prepared by vacuum evaporation,have been investigated as novel electron donor layers in two-layer photovoltaic cells.UV-Vis absorptions show red-shifted and broadened absorptions of the vacuumevaporated films as compared with those of the corresponding solutions and spin-coating films,which is beneficial for photovoltaic properties.X-ray diffraction (XRD) and differential scanning calorimetry (DSC) measurements show that the vacuum-evaporated films are almost amorphous.Two-layer photovoltaic cells have been realized by the thermal evaporation of 7T and 11T as donors and N,N bis(1-ethylpropyl)-3,4:9,10-perylene bis(tetracarboxyl diimide) (EPPTC) as an acceptor.An energy conversion efficiency (ECE) of 0.18% of the cell based on 7T with an irradiation of white light at 100 mw/cm 2 has been demonstrated by the measurements of current (I)-voltage (V) curves of the cells to be higher than the ECE of the reference system based on donor dihexylterthienyl (H3T) that is linear and without α,β linkage.
White organic light-emitting diodes with a blue emitting material fluorene-centred ethylene-liked carbazole oligomer(Cz6F) doped into polyvinyl carbazole(PVK) as the single light-emitting layer are reported.The optical properties of Cz6F,PVK,and PVK:Cz6F blends are studied.Single and double layer devices are fabricated by using PVK:Cz6F blends,and the device with the configuration of indium tin oxide(ITO)/PVK:Cz6F/tris(8-hydroxyquinolinate)aluminium(Alq3)/LiF/Al exhibits white light emission with Commission Internationale de l' ' Eclairage chromaticity coordinates of(0.30,0.33) and a brightness of 402 cd/m 2.The investigation reveals that the white light is composed of a blue-green emission originating from the excimer of Cz6F molecules and a red emission from an electroplex from the PVK:Cz6F blend films.
