SolFocus has designed and built a flexible and adaptable solar flash tester capable of reaching in excess of 2500x suns
flux using a commercially available Xenon flash and power supply. Using calibrated isotype cells and photodetectors,
the intensity and color balance of the flash are controlled through software algorithms that compensate for tube aging
and thermal drift. The data acquisition system dynamically normalizes each of the 1600 I-V data pairs to the lamp
intensity during each flash. Up to 32 cells can be measured simultaneously, with a flash re-cycle time of 3 seconds. The
dynamic current range is 100μA to 10A over 0 to 5V. Test ranges are limited by user input through a modern GUI
screen. The system is mated to a commercially available probe station tester which allows automated testing of up to
150mm diameter wafers, and is capable of testing a 4000 cell wafer in less than 8 minutes. The core software and optical
components are easily adaptable to receiver and full panel testing as well. Data on the calibration and performance of
the flash tester, the dynamic range achieved in test, and throughputs obtained during operation are presented.
Optical cavity effects have a significant influence on the extraction efficiency of InGaN/GaN quantum-well-heterostructure flip-chip light-emitting diodes (FCLEDs). Light emitted from the quantum well (QW) self-interferes due to reflection from a closely placed reflective metallic mirror. These interference patterns couple into the escape cone and cause significant changes in the extraction efficiency as the distance between the QW and the metallic mirror varies. In addition, the radiative lifetime of the QW also changes as a function of the distance between the QW and the mirror surface. Experimental results from packaged FCLEDs, supported by optical modeling, show that a QW placed at a neighboring position corresponding to a minimum in overall light extraction. Furthermore, the optical model and experimental data are used to estimate the absolute internal quantum efficiency.
High-power light-emitting diodes (LEDs) in both the AlInGaP (red to amber) and the AlGaInN (blue-green) material systems are now commercially available. These high-power LEDs enable applications wherein high flux is necessary, opening up new markets that previously required a large number of conventional LEDs. Data are presented on high-power AlGaInN LEDs utilizing flip-chip device structures. The high-power flip-chip LED is contained in a package that provides high current and temperature operation, high reliability, and optimized radiation patterns. These LEDs produce record powers of 350 mW (1A dc, 300 K) with low (<4V) forward voltages. The performance of these LEDs is demonstrated in terms of output power, efficiency, and electrical characteristics.
Currently, commercial LEDs based on AlGaInN emit light efficiently from the ultraviolet-blue to the green portion of the visible wavelength spectrum. Data are presented on AlGaInN LEDs grown by organometallic vapor phase epitaxy (OMVPE). Designs for high-power AlGaInN LEDs are presented along with their performance in terms of output power and efficiency. Finally, present and potential applications for high-power AlGaInN LEDs, including traffic signals and contour lighting, are discussed.
A new class of LEDs based on the AlGaInP material system first became commercially available in the early 1990's. These devices benefit from a direct bandgap from the red to the yellow-green portion of the spectrum. The high efficiencies possible in AlGaInP across this spectrum have enabled new applications for LEDs including automotive lighting, outdoor variable message signs, outdoor large screen video displays, and traffic signal lights. A review of high-brightness AlGaInP LED technology will be presented.