Interfacial properties and formation of a Schottky barrier at the CdS/PEDOT : PSS hybrid junction

The behaviour of a hybrid heterojunction (HJ) of an inorganic semiconductor cadmium sulfide (CdS) single crystal (102 Ω cm) and an organic conducting polymer poly(3,4-ethylenedioxythiophene) : poly(styrene sulfonic acid) (PEDOT : PSS) has been studied using electrical and photoelectrical measurements as well as ultraviolet photoelectron spectroscopy (UPS) with in situ Ar ion etching. Photovoltaic data and current-voltage characteristics demonstrated that the HJ is a Schottky diode with an electron barrier height ca ψb = 0.5 eV. The estimates based on the energy balance at the interface allowed us to assert on the presence of an interfacial dipole with an energy offset of -0.3 eV. A dipole barrier of the same magnitude was also clearly revealed from the UPS measurements directly.