Organic films deposited on Si p-n junctions: Accurate measurements of fluorescence internal efficiency, and application to luminescent antireflection coatings

Ultraviolet (UV) optical pumping followed by fluorescence wavelength downconversion of thin film organic light emitting materials deposited directly on the surface of Si p-n junction diodes is found to be an accurate and rapid means to determine the film internal fluorescence efficiency, By measuring the photoresponse of the Si detectors in the UV, rye find that the organic light emitting films of aluminum tris-(8-hydroxyquinoline) (Alq(3)), N,N'-diphenyl-N,N'-bis-(3-methylphenyl)-1,1'-biphenyl-4,4'-diamine, and bis-(8-hydroxyquinaldine)-chlorogallium (Gaq(2)'Cl), have internal fluorescence efficiencies of 0.30+/-0.05, 0.35+/-0.03, and 0.36+/-0.03, respectively. It has also been found that the organic films can be grown to a thickness which optimizes UV light conversion and can, at the same time, serve as antireflection coatings in the visible spectral region, thereby resulting in enhanced Si photodiode sensitivity extending from the UV to the infrared. (C) 1996 American Institute of Physics.