RESUMO
Zinc oxide nanowires (ZnO NWs) possess a unique one-dimensional (1D) morphology that offers a direct pathway for charge transport. In this article, we present the first application of the real-time time-dependent density functional tight-binding (real-time TD-DFTB) method for a model hybrid system consisting of a catechol molecule adsorbed on a ZnO nanowire. The rationalization of the photoinduced electron injection to the 1D nanostructure is attained through quantum dynamics simulations, stressing the role of charge transfer in the new optical transitions upon dye adsorption. We provide a momentum-resolved picture of the photoexcitation dynamics, highlighting the charge accumulation in certain k-points, which could improve our understanding of these ultrafast processes. Finally, in the context of dye-sensitized solar cells (DSSCs) based on ZnO NW arrays, we provide a method to calculate the photoresponse obtaining similar results to experiments. This work paves the way towards the fast and accurate theoretical design of 1D optoelectronic nanodevices.
RESUMO
We present a method based on a time-dependent self-consistent density functional tight-binding (TD-DFTB) approach, able to predict the quantum efficiency of the photoinjection process in a dye-TiO2 complex from a fully atomistic picture. We studied the process of charge transfer of three systems with different dyes: catechol (CAT), alizarin (ALZ) and FSD101. Each system was excited with lasers of different energies in the range of 300-2500 nm, studying the efficiency of the induced charge transfer process at the incident energies. We show that the perturbation can produce either hole transfer or electron transfer from the dye to the nanoparticle, therefore affecting the efficiency of the charge transfer in the solar cell when illuminated by broadband radiation.