Characterization of new red dopants for red color OLED

Abstract

New type red dopants N,N′-bis[4-(N,N-dimethylamino)-benzylidine]diaminomaleonitrile (M), N,N′-bis[8-hydroxy-1,1,7,7-tetramethyljulolidine]diaminomaleonitrile (R-11a) have been synthesized and used as a red dopant for red color OLED with narrow full-width at half-maximum (FWHM). The M and R-11a were synthesized by the reaction between diaminomaleonitrile and benzaldehyde in acetic acid. They showed more narrow full-width at half-maximum(FWHM) than asymmetric DCM series because they had a symmetric structure. Their photoluminescence and electroluminescence properties were examined and compared. The PL and EL peaks of films consisted of Alq3 and dopants were 620 nm (M), 624 nm (M) and 660 nm (R-11a), 660 nm (R-11a), respectively. Red organic light emitting devices(OLEDs) with these rede dopants have been fabricated. OLEDs have a configuration of ITO/TPD/Alq3:dopant/Alq3/LiF/Al. The electrical and optical properties of the devices were investigated.