Realization of large open circuit voltage in organic photovoltaic cells by introducing a fluorescent dye layer

Small-molecule organic photovoltaic (OPV) cell with a large open circuit voltage (V_OC) has been achieved by introducing 4-(dicyanomethylene)- 2-t-butyl-6-(1,1,7,7-tetramethyljulolidyl-9-enyl)-4H-pyran (DCJTB) as donor layer. In order to obtain large V_OC of standard copper phthalocyanine (CuPc)/C₆₀ OPV cell, a very thin layer of DCJTB was inserted between CuPc and C₆₀. It was found that the device formed multicharge separation interfaces. The VOC of device with 2 nm DCJTB layer was increased from 0.44 to 0.58 V. Also, the atomic force microscope (AFM) 3D-images of the donor surfaces were characterize to discuss OPV cell performance improvement. Furthermore, the absorption spectrum shows that an additional thin DCJTB layer enhances the light harvest capability of the cell.