Improved luminescent efficiency of a red organic dye with modified molecular structure

By introducing two methyl groups into 6 and 7 positions of the chromene group of a red fluorescent dye, 4-dicyanomethylene-2 (p-diphenylaminostyryl)-chromene (DCCPA), we have successfully synthesized a red organic materials, 4-dicyanomethylene-6,7-dimethyl-2 (p-diphenylaminostyryl)-chromene (DCCMPA) of considerably better florescence properties than DCCPA. Both photoluminescent (PL) and electroluminescent (EL) properties of DCCPA and DCCMPA have been examined and compared. The PL quantum yield of DCCMPA is 21% higher than that of DCCPA. The devices with DCCMPA doped into tris (8-quinolinolato) aluminum (Alq3) also show higher efficiencies than the DCCPA doped devices. Based on these experimental results, some useful guidelines for molecular design of red organic materials for EL applications are discussed.