The paper's purpose is to describe and discuss the study of LED diodes, measured with the help of the TERALED system. A short description of the measurement system is given. Four batches of 5 mm LEDs and two batches of PowerLED diodes are measured and the comments and discussion of the measured results are given. The experiments show clearly that some manufacturer's LEDs do not match the parameters given in the datasheet. The reasons are not clear, but it seems to us that the problems of degradation of the construction materials of LEDs are not connected with the degradation of the semiconductor material itself.

LED technology has evolved at a fast pace within the last years; offering already LED devices with luminous efficacy of 150 lumens per watt or even more. Based on studies about LED light output dependence on forward current and (junction) temperature, the optimal model for simulating the light output of monochromatic LEDs has been developed. Available solutions in literature are analyzed and modified to relate their parameters to LED properties, which could be predicted with a SPICE-like electrical model of LEDs. Experimental blue and red high power LEDs are measured using the state-of-the-art measurement systems -T3Ster and TERALED in a combined measurement setup and optimization algorithms are used for calculating additional fitting parameters for the developed model. The modeled results are compared against the experimental measurements and an excellent agreement is found between the simulated and measured output of monochromatic LEDs.