LOW-TEMPERATURE ELECTRON INJECTION AND SPACE-CHARGE-LIMITED TRANSIENTS IN ANTHRACENE CRYSTALS

A solid electrode has been prepared able to efficiently inject electrons into anthracene crystals at temperatures as low as 77°K. Currents as high as 10-2 A·cm-2 may be injected with no evidence of saturation. No activation energy is associated with the injection process, the current-temperature dependence is determined only by the trap distribution of the crystal. Using this electrode the temperature dependence of the electron mobility has been measured from 300 to 170°K. The results corroborate those from phototechniques, namely, as temperature decreases the electron mobility increases along the a and b crystal axes and decreases slightly along the c 1 axes. At low temperatures, a second maximum in the current transient along the a and b directions is observed.