PHOTOLUMINESCENCE AND ELECTROLUMINESCENCE OF SQUARYLIUM CYANINE DYES

A series of squarylium cyanine dyes (Sq1, Sq2 and Sq3) were synthesize d to explore their applications in organic electroluminescence devices (ELDs) with the aim of achieving highly efficient red emission. The a bsorption and fluorescence spectra of squarylium cyanine dyes (Sqs) in organic solvents, as well as their interaction with S-hydroxyquinolin e aluminum (Alq) in solution and in film, were investigated to help un derstand the EL mechanism. The basic device structure consists of a ho le-transport layer (HTL) of ,N'-bis(3-methylphenyl)-1,1'-diphenyl-4,4' -diamine (TPD) and an emission layer (EML) of Sq-doped Alq. By the dop ing method, the EL color can be readily tuned from green (EL of Alq) t o red (EL of Sq) upon varying application of voltage. The EL mechanism is suggested to be associated with the energy transfer from the excit ed Alq to the dopant Sq. (C) 1997 Elsevier Science S.A.