Efficiency analysis of light emitting diodes based on material properties and structures

Studies on efficiency and performance of light-emitting diodes (LEDs) involves the complicated interactions of optic, electronic, magnetic, quantum and thermal characteristics of materials and structures of LEDs. Therefore, efficiency and performance of LEDs are generally investigated by measurements and aided via theoretical analysis. While the analytical formulas of material properties and structures of LEDs are sensitive and difficult to obtain for calculating the efficiency and performance of LEDs, it is still essential for academic and technological developments to propose the analytical model of efficiency study based on material properties and structures of LEDs. With the progress in the analytical formulas of material properties and structures of LEDs, the analytical method for the study on the efficiency of LEDs is proposed in this paper and applied to the efficiency predictions of AlGaInP and InGaN QW LEDs. The results are compared with the available measured data and agree with these obtained by measurements. The results indicate that the variation of efficiency of InGaN LED with forward current increases very rapidly at initial forward current and then slowly decreases with the increasing forward current. However, efficiency of AlGaInP LED hardly decreases with the increasing forward current after the rapid increase of efficiency at the initial forward current. The possible reason is that the series resistance of AlGaInP LED is lower than that of InGaN LED.