Hole and Electron Transport in Chloroaluminum Phthalocyanine Thin Films

Thin films (∼1.2 μm) of chloroaluminum phthalocyanine (ClAlPc) are vacuum sublimed at sublimation rates of 200 and 1000 A/min on substrates maintained at two temperatures, Ts = 25 and 95 °C. Hole mobilities are very well described by the disorder formalism of Bassler and co-workers. As sublimation rate decreases or Ts increases, σ, the width of density of states, decreases to a minimum of 0.052 eV. “Intrinsic” mobility, μ00, increases concomitantly, as do measured mobilities, reaching ∼1 × 10-3 cm2/(V s). Positional disorder, Σ, is less affected by the sublimation conditions. Results, as discussed in the context of previous work, indicate an increased organization of molecules in slowly deposited films on heated substrates. An anomalous increase of mobilities, as temperature decreases below a reversal temperature, is confirmed for all samples. The reversal temperature itself increases with increased film organization, from 213 to 253 K, consistent with greater coplanar overlap of Pc macrocycles on cooling...