1,8-Naphthalimides for non-doping OLEDs: the tunable emission color from blue, green to red

Substitution at the 4-position of 1,8-naphthalimide with electron-donating groups can increase fluorescent quantum yields and change emissive wavelengths from blue to red. Based on this molecular design concept, novel naphthalimide derivatives containing Schiff base moiety were prepared by condensing 4-hydrazino-1,8-naphthalimides with the aldehydes. Amino conjugation between the 4-amino-1,8-naphthalimide and the substituted moiety resulted in red shift of the absorption and fluorescence maximum wavelengths in the acetonitrile solution and in the net solid film. In the meantime, concentration-quenching effect of fluorescence for common luminescent materials was avoided. Some of these dyes emit brilliant red fluorescence in solid films and were used as non-doping emissive materials to fabricate electroluminescence devices. Based on these results, guidelines for the molecular design of non-doping red emissive materials for OLED applications are presented in this paper.