A photovoltaic response of a Schottky diode based on the conducting polymer PEDOT:PSS and inorganic semiconductors

Abstract

Hybrid organic-inorganic heterostructures have been produced using the conducting polymer PEDOT:PSS and three types of semiconductor single crystals, i.e., high-ohmic and low-ohmic cadmium sulphide (CdS, n-type semiconductor) and low-ohmic cadmium telluride (CdTe, p-type semiconductor). A photovoltaic (PV) response was observed upon light illumination of both CdS/PEDOT:PSS and CdTe/PEDOT:PSS heterojunctions. Photocurrent spectra unequivocally evidenced the main contribution of band-band transitions of inorganic crystals to the PV response, and current-voltage measurements indicated that band bending due to a depleting region at the surface of the crystals takes place. The suggested band bending was consistent with the model of the vacuum level alignment only at the interface of the low-ohmic CdS crystal and the polymer, which results in formation of a Schottky barrier responsible for the PV response. However, the analogous band bending for high-ohmic CdS and p-type CdTe crystals could be associated only with the Fermi level pinning regime at the semiconductor interfaces.