Will LEDs achieve high light output?
The first LEDs were quite small, with the semiconductor element only about 0.25 millimeters on edge. More recent designs have elements that are 1 millimeter on edge — significantly larger but still quite small. One of the limitations of large sizes is the problem of imperfections in the materials forming the semiconducting elements when they are deposited on much larger substrates; these imperfections greatly reduce efficiency. Thus, LEDs consisting of a single element will not likely exceed the light output of conventional light sources in the near future. However, LEDs with multiple elements packaged together into a single device are already available on the market; these devices are already approaching the lumen outputs found in some low-wattage incandescent lamps and future products will likely continue to offer greater light output.