Non-doped long-wave red electroluminescence for fumaronitrile with fluorenyl or biphenyl group

Abstract

The long-wave red emitters SFPAFN (bis(4-(N-(9,9′-spirobifluorenyl-2)-3,5- dimethylphenylamino)phenyl)fumaronitrile), BPFAFN (bis(4-(N-(9,9′-diethyl-2- fluorenyl)diphen-4,4′-ylamino)phenyl)fumaronitrile), and BBPAFN (bis(4-(N,N′-bis(diphen-4,4′-yl)amino)phenyl)fumaronitrile) were synthesized. The bulky, non-planar and large conjugated spirobifluorenyl, fluorenyl or biphenyl amino substituent formed steric torsional hindrance to restrict intermolecular aggregation. These promoted hole transport ability and luminous efficiency, and tuned the long-wave red emission successfully. The non-doped red devices for donor–π–acceptor–π–donor SFPAFN, BPFAFN and BBPAFN showed electroluminescent (EL) peaks at 680, 692, and 680 nm with the maximum luminance efficiencies of 3.33, 3.61, and 3.13 cd/A, respectively. The EL emission was redshifted and EL efficiency was improved more effectively for BPFAFN than that for SFPAFN or BBPAFN. These compounds were excellent long-wave red emitters with hole-transporting properties. Furthermore, the main EL parameters of similar non-doped red OLEDs for arylamino fumaronitrile derivatives were compared briefly.