A Study of Enhancement Techniques for Light Extraction Efficiency of Light Emitting Diodes
Light extraction efficiency has become first order design constraint for LEDs and its enhancement has always been a challenge for researchers. This affects the life of LEDs as well as optical output and various techniques for its enhancement have been reported. Methods for maximizing the efficiency of LEDs are typically based on enhancement of internal and external quantum efficiency. In our paper, we report efficiency enhancement based comparative study of LEDs which are grown by different techniques. Firstly the techniques dealing with improvement of internal quantum efficiency and secondly the techniques for increasing ratio of photons leaving the LED to those created in active region (enhancement of external quantum efficiency) are reviewed.
Abstract A synthesis and stereochemistry confirmation of a constituent recently isolated from the whole plant Isodon excisus is reported. An enantioselective catalytic boron-mediated reduction of an α-bromoketone was utilized in the key synthetic transformation. The methodology described herein was also used for the synthesis of the natural product's enantiomer and several derivatives. In addition, the compounds were evaluated for inhibitory activity in a caspase induction assay. The natural product was found to be devoid of activity, but several derivatives had moderate inhibitory activity (EC 50