The Variation of the Carrier Recombination Region with Carrier Density in Anthracene Crystals

The time dependence of slow electroluminescence has been used as an experimental probe for studying the physical characteristics of the recombination region in anthracene. Under conditions where two injecting contacts are used, and neither carrier is trapped to a large extent, the recombination zone is found to occupy approximately 0.3 of the crystal volume for current densities of 10−5-10−8 amps cm−2. When forced hole injection is used, the recombination volume at low currents decreases, particularly at low temperatures. This decrease in recombination volume is discussed in terms of carrier trapping and filament formation.