LOW-MOLECULAR ORGANIC GLASSES FOR BLUE ELECTROLUMINESCENCE

Spiro-linkage is used to modify the steric demand of low molecular org anic compounds to improve their processability and morphologic stabili ty, while their electronic properties are retained. These spiro-linked compounds form stable nonpolymeric organic glasses with high glass tr ansition temperatures, usually associated with amorphous polymers. Hig h quality amorphous films with high morphologic stability can be prepa red with these spiro-linked luminescent or charge transport materials by conventional spin-coating techniques as well as by vapor deposition . Based on these spiro-compounds, blue electroluminescence devices wit h high color purity, high brightness and low turn-on voltage are prese nted. A blue light-emitting two-layer device, fabricated by combining a hole transporting spiro-TAD with an electron transporting spiro-PBD, shows a turn-on voltage at 2.7 V and a luminance of 500 cd/m(2) at 5 V. (C) 1997 Elsevier Science S.A.