Efficiency improvement in light-emitting diodes based on geometrically deformed chips

We propose LEDs based on geometrically deformed chips of which the horizontal cross-section is either rhomboidal or triangular and, in addition, side walls may also be slanted. In such deformed chips, the photon trajectory changes with each reflection off the wall and, as a result, the continued total internal reflections as observed in conventional rectangular cubic chips are suppressed. Monte Carlo photon simulation that has been developed for this study shows that the photon output coupling or extraction efficiency in the proposed design is improved by about 100 to 120 % over that in conventional LEDs. Improved photon emission has also been experimentally observed in LED lamps that have been deformed by filing away a portion of the chip and encapsulant epoxy as well. The rhomboidal or triangular chips, in addition, may be integrated into super-bright LED lamps, in which the chips are arrayed such that the side walls of neighboring chips face each other obliquely, virtually eliminating the optical coupling between neighboring chips. The minimized optical coupling would prevent the efficiency of the integrated lamps from degrading significantly below that in single chip LED lamps.