First Principles Study of the Structural and Electronic Properties of the ZnO/Cu₂O Heterojunction

Abstract

Many materials have been used in nanostructured devices; the goal of attaining high-efficiency thin-film solar cells in such a way has yet to be achieved. Heterojunctions based on ZnO/Cu 2 O oxides have recently emerged as promising materials for high-efficiency nanostructured devices. In this work, we are interested in the characterization of the surface and interface through nano-scale modeling based on ab initio (Density Functional Theory (DFT), Local Density Approximation (LDA), Generalized Gradient Approximation (GGA-PBE), and Pseudopotential (PP)). This study aims also to build a supercell containing a ZnO/Cu 2 O heterojunction and study the structural properties and the discontinuity of the valence band (band offset) from a semiconductor to an-other. We investigate crystal terminations of ZnO (0001) and Cu 2 O (0001). We calculate the energies of the polar surfaces and the work function in the c-axis for both oxides. We built a zinc oxide layer in the wurtzite structure along the [0001] direction, on which we placed a copper oxide layer in the hexagonal structure (CdI 2 -type). We choose the method of Van de Walle and Martin to calcu-late the energy offset. This approach fits well with the DFT. Our calculations give us a value that corresponds to other experimental and theoretical values.