Space charge limited hole transport in evaporated thin films of α-H2Pc

Abstract

Thin films of metal-free phthalocyanine (H2Pc) have been grown on different substrates via physical vapor deposition. The films grown at room temperature have been shown to have α-polymorph, which was converted into β-phase when the films were subjected to thermal treatment at 608 K for 2 h. The phase transition was confirmed via extensive characterization of the treated and untreated films. This paper describes hole transport investigations in α-H2Pc thin films for which the samples were prepared in hole only configuration and current density–voltage (J–V) characteristics were studied at different temperatures for two different thicknesses of α-H2Pc. The investigations show that the hole transport in α-H2Pc is governed by space charge limited conduction with single-level traps in the energy space. The studies enabled us to calculate the hole mobility in H2Pc which was observed to be independent of temperature and electric field.