Impedance Spectroscopy and Dielectric Relaxation of Imidazole-Substituted Palladium(II) Phthalocyanine (ImPdPc) for Organic Solar Cells †

Abstract

In this study, we investigated the potential of palladium tetrakis (imidazole) phthalocyanine (PdPc(Imz)4) for use as an organic semiconductor for improving the photovoltaic performance. In order to get more information about the prevailing model of the conduction mechanism (correlated barrier hopping (CBH)) for PdPc(Imz)4, electrical impedance measurements were performed at different temperatures and the obtained data were simulated by the Kohlraush Williams Watt (KWW) approach. Theoretical studies (density functional theory (DFT)) were performed and molecular electrostatic potential (MEP) maps were also extracted to understand the relationship between the molecular structures and the molecular electronic structure of PdPc(Imz)4 and its semiconductor properties. Furthermore, studies on the AC electrical process as a function of temperature highlighted a hopping charge transport according to an equivalent electrical circuit composed of a parallel constant-phase element (CPE), capacitance in the grain boundary layer (Cg), and resistance of the grain boundary (Rg). To improve interpretation of the results, an in-depth analysis of the behavior of the electric transport was conducted. As a result, the correlated barrier hopping (CBH) conduction mechanism was shown to be the most suitable predominant conduction mechanism.