Very broad white-emission spectrum based organic light-emitting diodes by four exciplex emission bands

White light is emitted by an organic light-emitting diode by inserting two blend layers of m-MTDATA:Al(DBM)(3) and TPD:Bphen between an m-MTDATA hole-transporting layer and a Bphen electron-transporting layer, where m-MTDATA, TPD, Al(DBM)(3), and Bphen are 4,4('),4('')-tris[methylpheny(phenyl)amino]-triphenylamine, N,N(')-bis(3-methylphenyl)-N,N(')-diphenylbenzidine, tris(dibenzoyl methane)-aluminum, and 4,7-diphenyl-1,10-phenanthroline molecules, respectively. The white-light spectrum consists of four broad bands that arise from blue-emitting TPD/Bphen, green-emitting m-MTDATA/Bphen, orange-emitting TPD/Al(DBM)(3), and red-emitting m-MTDATA/Al(DBM)(3) exciplexes, respectively, and strongly overlap at 400-760 nm. Any monomer emission is not generated. A high-color rendering index of 94.1, Commission Internationale de l'Eclairage-1931(x,y) coordinates of (0.33, 0.35), and correlated color temperature of 5477 K were obtained at 10 V. Discussion is given for the formation mechanism of the four exciplexes.