Reduction of guided waves in ITO/glass interface of white organic light emitting diodes (WOLEDs): Layer optimization

A novel proposal for enhancement of light extraction efficiency in WOLEDs based on optimized photonic crystal structures

“…1, in which the outcome of the simulation is compatible with the previous theoretical results [16]. The portion of 50% transmitted light to the glass substrate is illustrated in Fig.…”

“…Second, much more increment or decrement of parameters will not always guarantee the achievement of better results, for example increment of height of rods only for limited values enhances transmission. Third, the lattice constant should be close to the vacuum wavelength of incident light [16], and finally if the Brillouin zone get closer to circle there will be more transmission and better results [16]. To prove our claim we started with basic structure of WOLED and then added rectangular, hexagonal and circular lattices to the ITO-glass interface.…”

“…In all structures the shape of rods are circular and the material used for rods and backfill are SiO 2 n sio 2 = 1.46 and SiN x n SINx = 1.95 respectively. In this research all layer's absorption and also dependency of refractive indexes to wavelength are considered whereas in the previously reported researches the refractive indexes were constant for simplicity [16]. The point source which is active for 20 fs and in the range of 400 nm 700 nm best models the behavior of a WOLED, considering 100% IQE [16].…”

“…In this research all layer's absorption and also dependency of refractive indexes to wavelength are considered whereas in the previously reported researches the refractive indexes were constant for simplicity [16]. The point source which is active for 20 fs and in the range of 400 nm 700 nm best models the behavior of a WOLED, considering 100% IQE [16]. Each side of the structure is modeled by perfectly matched layer (PML), except the metal cathode which is modeled by metal boundary condition to model its fine reflectivity and the mesh sizes are x = 15 nm, y = 15 nm and z = 10 nm, the monitor in glass substrate shows the transmission, also here we measured the absorbed light in the layers of WOLED, which is lost and out of reach.…”

“…In order to decrease the amount of TIR in glass-air interface one can use micro-lenses arrays [12,13] and get even better EQE. So far lots of efforts have been reported to reduce TIR in ITO-glass interface, such as using rough internal interfaces [11], high index substrate with micro-lenses arrays [12], using optimized multilayer structures [14], quasi photonic crystals [15] and photonic crystals [16,17].…”