Bulk Trapping States in β-Phthalocyanine Single Crystals

Abstract

From temperature dependence measurements of the SCLC and Ohmic current densities, the electron trapping levels in metal-free phthalocyanine have been determined in several ambients. In vacuum, traps with a density 5 × 1019 cm−3 located 0.38 eV below the conduction band have been observed. Associated with this level are donor sites with a density 2 × 1012 cm−3. In oxygen and hydrogen, trapping sites near the middle of the bandgap are observed. Thickness dependence measurements prove that the trapping sites are located at discrete energy levels. The results are extended to comment upon traps in copper phthalocyanine. The measurements indicate that the electron mobility is not temperature dependent up to 373°K.