Using a crystallization-inhibitor in organic electroluminescent devices
View Patent ↗An organic electroluminescent device includes an anode; a hole-transporting layer disposed over the anode, a light-emitting layer disposed over the hole-transporting layer for producing light in response to hole-electron recombination, and an electron-transporting layer disposed over the light-emitting layer. The device also includes a crystallization-inhibitor incorporated within the electron-transporting layer, wherein the crystallization-inhibitor prevents the electron-transporting layer from crystallizing during operation, and a cathode disposed over the electron-transporting layer.
1. An organic electroluminescent device, comprising:
a) an anode;
b) a hole-transporting layer disposed over the anode;
c) a light-emitting layer disposed over the hole-transporting layer for producing light in response to hole-electron recombination;
d) an electron-transporting layer disposed over the light-emitting layer;
e) a crystallization-inhibitor incorporated within the electron-transporting layer and wherein when the crystallization-inhibitor is an anthracene derivative, the concentration of the anthracene derivative is in the range greater than 25 percent by volume up to 50 percent by volume of the electron-transporting layer, wherein the crystallization-inhibitor prevents the electron-transporting layer from crystallizing during operation; and
f) a cathode disposed over the electron-transporting layer.
2. The organic electroluminescent device of claim 1 wherein the electron-transporting layer has a glass transition temperature (Tg) higher than 50° C.
3. The organic electroluminescent device of claim 1 wherein the crystallization-inhibitor includes an organic material having a glass transition temperature (Tg) higher than 70° C.
4. The organic electroluminescent device of claim 3 wherein the crystallization-inhibitor has an optical energy band gap wider than 1.5 eV.
5. The organic electroluminescent device of claim 3 wherein the crystallization-inhibitor includes 2-(1,1-dimethyethyl)-9,10-bis(2-naphthalenyl) anthracene (TBADN) or 9,10-di-(2-naphthyl) anthracene (ADN).
6. The organic electroluminescent device of claim 1 wherein the molecular ratio of the crystallization-inhibitor to the electron-transporting material in the electron-transporting layer is in the range of from 0.3 to 5.
7. The organic electroluminescent device of claim 1 wherein the electron-transporting layer includes 4,7-diphenyl-1,10-phenanthroline (Bphen), 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP), or other phenanthroline derivatives.
8. The organic electroluminescent device of claim 1 wherein the electron-transporting layer includes 2,2′-(1,1′-biphenyl)-4,4′-diylbis (4,6-(p-tolyl)-1,3,5-triazine).
9. The organic electroluminescent device of claim 1 wherein the electron-transporting layer contains a host electron-transporting material doped with Li, Na, K, Rb, or Cs.