High performance light-emitting devices

Abstract

A light emitting device in the form of a layered structure has a passive bottom multilayer stack including a cathode layer, a cavity layer including a light emitting region, a passive top multilayer stack including a hole transport layer, and a transparent anode layer. The passive bottom and top multilayer stacks are devoid of a light emitting layer. A transparent substrate, through which light is emitted from the device, is located over the top multilayer stack. At least one functional additional layer group in the passive top multilayer stack controls the reflectance of the passive top multilayer stack and phase changes occurring upon reflection from the passive top multilayer stack in the cavity layer.

1 . A light emitting device in the form of a layered structure comprising:
 a passive bottom multilayer stack including a cathode layer;   a cavity layer including a light emitting region;   a passive top multilayer stack including a hole transport layer, and a transparent anode layer,   said passive bottom and top multilayer stacks being devoid of a light emitting layer;   a transparent substrate located over said top multilayer stack and through which light is emitted from the device; and   at least one functional additional layer group in said passive top multilayer stack controlling the reflectance of the passive top multilayer stack and phase changes occurring upon reflection from said passive top multilayer stack in said cavity layer.   
     
     
         2 . The light emitting device as claimed in  claim 1 , wherein said at least one additional functional layer comprises alternate dielectric layers above said transparent anode layer. 
     
     
         3 . The light emitting device as claimed in  claim 2 , wherein said alternating dielectric layers are SiO 2  and TiO 2 . 
     
     
         4 . The light emitting device as claimed in  claim 1 , wherein said light emitting device is an OLED. 
     
     
         5 . A light emitting device in the form of a layered structure comprising:
 a passive bottom multilayer stack including a cathode layer;   a cavity layer including a light emitting region;   a passive top multilayer stack including a hole transport layer, and a transparent anode layer;   said passive bottom and top multilayer stacks being devoid of a light emitting layer;   a transparent substrate over said top multilayer stack through which light is emitted from the device;   at least one additional absorptive layer group in said top multilayer stack reducing the external reflectance of the passive top multilayer stack; and   a layer of conductive material having high reflectance and low absorption on the inside of said passive top multilayer stack to increase the internal reflectance of said passive top multilayer stack.   
     
     
         6 . The light emitting device as claimed in  claim 5 , wherein said absorbent layer group comprises a mixture of metal and dielectric. 
     
     
         7 . The light emitting device as claimed in  claim 5 , wherein said absorbent layer group comprises a semiconductor. 
     
     
         8 . The light emitting device as claimed in  claim 5 , wherein said at least one additional absorptive layer group comprises alternate dielectric and metal layers. 
     
     
         9 . The light emitting device as claimed in  claim 5 , wherein said conductive layer is a metal. 
     
     
         10 . The organic light emitting device as claimed in  claim 9 , wherein said metal is silver. 
     
     
         11 . The light emitting device as claimed in  claim 5 , wherein said light emitting device is an OLED.