Patent ID: 7863632

Claim:
A light emitting device comprising: a layered structure comprising a cavity layer containing a light emitting region sandwiched between passive bottom and top multilayer stacks, said passive bottom and top multilayer stacks being devoid of a light emitting layer; wherein the passive bottom multilayer stack includes a cathode and the passive top multilayer stack includes a hole transport layer and a transparent anode, wherein the passive top multilayer stack includes an additional functional layer group for increasing an internal reflectance of the passive top multilayer stack and the passive bottom multilayer stack includes an additional functional layer group for reducing reflectance from the cathode; wherein a top transparent substrate through which light is emitted from the device is located above the top multilayer stack; and wherein said layered structure is constructed such that the product of phase factors Î¾ 1 and Î¾ 2 is greater than 80% at the center of at least one light emitting region and for a normal viewing angle, wherein Î¾ 1 = ( 1 + 4 â¢ R a - â¢ R b + â¢ sin 2 â¡ ( Î± 1 - Ï† a - + Ï† b + 2 ) â¢ â…‡ - 2 â¢ Î² 1 ( 1 - R a - â¢ R b + â¢ â…‡ - 2 â¢ Î² 1 ) 2 ) - 1 Î¾ 2 = 1 - 4 â¢ R b + â¢ sin 2 â¡ ( Î± 2 - Ï† b + 2 ) â¢ â…‡ - 2 â¢ Î² 2 ( 1 + R b + â¢ â…‡ - 2 â¢ Î² 2 ) 2 { Î´ 1 = 2 â¢ Ï€ Î» â¢ ( n - ik ) â¢ d â¢ â¢ cos â¢ â¢ Î¸ cavity = 2 â¢ Ï€ Î» â¢ nd â¢ â¢ cos â¢ â¢ Î¸ cavity - i â¢ 2 â¢ Ï€ Î» â¢ kd â¢ â¢ cos â¢ â¢ Î¸ cavity = Î± 1 - iÎ² 1 Î´ 2 = 2 â¢ Ï€ Î» â¢ ( n - ik ) â¢ x â¢ â¢ cos â¢ â¢ Î¸ cavity = 2 â¢ Ï€ Î» â¢ nx â¢ â¢ cos â¢ â¢ Î¸ cavity - i â¢ 2 â¢ Ï€ Î» â¢ kx â¢ â¢ cos â¢ â¢ Î¸ cavity = Î± 2 - iÎ² 2 where R a âˆ’ and R b + are the reflectance of the passive top and bottom multilayer stacks respectively, Ï† a âˆ’ and R b + are phase changes on reflection for the passive top and bottom multilayer stacks respectively, Î± 1 and Î² 1 are respectively the real and imaginary parts of a phase thickness, Î´ 1 of said cavity layer, Î± 2 and Î² 2 are respectively the real and imaginary parts of the phase thickness, Î´ 2 , of said light-emitting region at an operating wavelength, Î», of the light emitting device, x is the mean distance of said light emitting region from the passive bottom multilayer stack, n and k are respectively a refractive index and an absorption coefficient of said cavity layer, Î¸ cavity is the emitting angle inside the cavity layer, and d is a physical thickness of said cavity layer.