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

Abstract

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 φb = 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.