Reddish orange light-emitting diodes made with N,N′-bis (1-naphthyl) -3,4,9,10-perylenbis(dicarboximide)

The electroluminescence (EL) of N,N′-bis(1-naphthyl)-3,4,9,10-perylenbis(dicarboximide) (BPD) is reported. BPD is an electron acceptor. Red emission from multilayered light-emitting diodes (LEDs) using BPD as light-emitting layer with a maximum brightness of 26 cd/m2 was observed. The metal materials of the cathode have an effect on both the turn-on voltage and the peaks and shapes of the EL spectra of the devices. This implies that some kind of interaction exists between BPD and the cathode. In LEDs with both hole transport layer and electron transport layer, it was found that the peaks and shapes of the EL spectra of BPD change greatly with the applied bias. When the forward biased voltage is low, the EL emission colour is scarlet. As the voltage increases, the emission colour gradually blue-shifts to reddish orange. Fine structure of the EL spectrum was observed.