Charge Transfer from Alq₃-5Cl to Graphene Oxide in Donor–Acceptor Heterostructures

Abstract

This paper describes an alternative active layer for the solar cells based on the organometallic compounds in two configurations: bulk heterojunction and donor/acceptor junction between the organometallic compounds as the electron donor and carbon-based layer as the electron acceptor. Both configurations depend on the band alignment which ensures optimal charge transport towards electrodes in the sandwich structures of these active layers, but the optimization also depends by the exciton diffusion length which limits the thicknesses of the active layer. In the bulk heterojunctions, the exciton diffusion length could be extended to 100 nm which allows a better efficiency then bilayer structures. The photoconductive behaviors of these two configurations have shown the superiority of the bulk heterojunctions, increasing the intensity of the measured photocurrent. The redshift of the photoluminescence of Alq3-5Cl in the bulk heterojunctions reveals a better charge transfer towards the acceptor layer, in this case, formed from graphene oxide. The alternative of organometallic compounds as donor materials ensures a better thermal and chemical stability compared with other organic materials like perovskites.