Theoretical and Experimental analysis of ZnPc for its local ordering and electronic structure

Abstract

Zinc Phthalocyannine (ZnPc) has been investigated intensely for fabricating plastic solar cells, and there are very limited reports available relating molecular structure and its corresponding macroscopic properties linked with simulation and electronic structure. In fact, our previous reports have demonstrated a partial ordering of the ZnPc molecules [1]. As a continuation of our previous work, we report here the structural determination of atomic and electronic distribution in this material, and a detailed analysis of its involvement in interactions that produce local domains in partial periodic structures. The use of high resolution transmission electron microscopy (HRTEM) and digital processing based on the frequency selection allowed us to distinguish the contrast from local arrays of fringes with distances around 0.37 and 0.35 nm between them. From the quantum mechanical calculations and approximations for single molecules and from classical molecular mechanics for two to six molecule arrays, we identified the type of ordering and the effects on the corresponding frontier orbital (HOMO and LUMO) and the electrostatic potential. The calculated models and a simulation of the HRTEM images demonstrate that the molecular arrays observed in the samples are determined by the electrostatic interactions and the production of arrays influence significantly the optical and electronic properties of the ZnPc material.