Light extraction of organic light emitting diodes by defective hexagonal-close-packed array

Defective silica sphere arrays having locally hexagonal-closed-packed structure but lack of long range ordering were incorporated into organic light emitting diodes as grating to extract the waveguided light trapped in the indium tin oxide/organic layers and the glass substrate. Using these defective hexagonal-closed-packed gratings for light extraction, broad band lambertian emitters are obtained due to the periodicity broadening and the random orientation in the gratings, resulting in enhancements in current and power efficiencies by a factor of 1.7 and 1.9, respectively. An organic light-emitting diode device with a defective hexagonal-close-packed array can effectively extract the waveguide modes over all emission wavelengths and angles without spectral changes and directionality because of the broadening of the periodicity and the random orientation from the defective array pattern.