Light-emitting diodes (LEDs) can function as very stable, spectrally selective photodiodes in simple Sun photometers. This technology has now been applied to inexpensive solar radiometers designed to measure full-sky solar irradiance at various wavelengths.
© 2000 Optical Society of America
Forrest M. Mims, "Solar Radiometer With Light-Emitting Diodes As Spectrally-Selective Detectors," Appl. Opt. 39, 6517-6518 (2000)