Observation of Photovoltaic Effects in Bright Red Organic Electroluminescent Diodes Doped with Red Dopant

Photovoltaic (PV) effects for red bright organic light-emitting diodes (OLEDs) in which the red light emitted from the dopant 4-(dicyanomethylene)-2-t-butyl-6-(1,1,7,7-tetramethyljulolidyl-9-enyl)-4H-pyran (DCJTB) have been observed. The OLEDs show organic photovoltaic properties. At the optimum doping concentration, the main eletroluminescence parameters including the maximum brightness and the maximum luminous efficiency under current density of 20 mA/cm² are 3280 cd/m² and 1.54 cd/A, respectively. When irradiated by a 365-nm UV-light (4 mW/cm²), the device exhibits the PV parameters of the open-circuit voltage 1.4 V, short-circuit current 2.9 μA/cm², fill factor 0.22, and power conversion efficiency 0.022%. Effects of every organic layer, especially the doped DCJTB on the PV performance, are also discussed. It is expected that the research for the PV property of the small molecular doping OLEDs will be of benefit for flat panel display technology in the future.