DEPOSITION AND CHARACTERIZATION OF MICROSTRUCTURED SILICA LAYER ON GLASS FOR LIGHT EXTRACTION APPLICATION IN LED

Abstract

Light emitting diodes (LEDs) are of keen interest as their energy saving property is attracting several researchers because of enormous energy crisis we are facing. Organic light emitting diode (OLED) have attracted much attention due to their advantage such as low power consumption, high internal quantum efficiency, high brightness, high contrast and low cost than those of inorganic or semiconductor based LEDs. But only 20% of the generated photons in organic layer are extracted out from the device. Thus, light extraction efficiency improvement is required before it can make any significant impact. The primary aim of this thesis is to enhance the light extraction efficiency of LEDs/OLEDs. To increase the light extraction efficiency, we have introduced microstructured silica layer between glass substrate and indium tin oxide (ITO). By introducing silica layer between glass and ITO, more light can be extracted from the device. As silica layer is porous, more light can couple from high index layer of OLED into the glass substrate. We have studied the effect of microstructured silica layer deposited on glass substrate. Surface morphology of the prepared samples was done by AFM and FESEM. Transmission of prepared samples was carried out by UV-Vis spectrophotometer. Enhancement in transmission was seen with the prepared samples. We have also tried to fabricate gratings on the microstructured silica film. For fabricating gratings on the silica film, nanoimprint lithography is employed. We have studied the effect of gratings on silica film. We have also studied the optical characteristics of gratings on silica film.