X-shape oligo(thiophene)s as donor materials for vacuum-deposited organic photovoltaic cells

【摘要】：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.