Alignment of energy levels in dye/semiconductor interfaces byGWcalculations: Effects due to coadsorption of solvent molecules

Abstract

The performance of dye-sensitized solar cells is tightly linked to the relative energy level alignment of its constituents. In this paper the electronic properties of a model of dye-sensitized solar cell are studied by accurate first-principle calculations taking into account many-body effects beyond density-functional theory. The cell model includes one layer of co-adsorbed solvent (water or acetonitrile) molecules. Solvent molecules induce an upwards energy shift in the TiO 2 bands; such a shift is larger in the case of acetonitrile. The accurate determination of the energy levels allows the theoretical estimation of the maximum attainable open circuit voltage (V oc ).

Structure and Energetics of Dye-Sensitized NiO Interfaces in Water from Ab Initio MD and Large-Scale GW Calculations

“…This effect is due to geometrical distortion of the C343 structure driven by the deprotonation and bonds with the Ni atoms of the NiO surface and by the interactions between periodic images along the a and b directions. 56 However, these interactions are not to be regarded as spurious because the surface dye concentration adopted in our model of the interface (∼ 1 molecule/ 0.70 nm 2 ) is in line with the typical experimental surface coverage employed in DSSCs. 111,112 As far as the VBM-HOMO difference is concerned, a negative driving force of -0.3 eV is predicted for the interface in gas phase.…”

“…[48][49][50] However, this approximation, as all DFT based methods, neglect dynamical polarization or image charge effects, which can be rather pronounced for the dye electronic states in the dye@SC interface and can critically influence the energy level alignment. 46,[55][56][57][58] These higher-order effects, as well as the spatial dependence of the electronic correlation, can be accounted for by using more refined approximations, such as many body perturbation theory (MBPT) based methods, where the dynamical polarization response to the addition or to the removal of a particle are rigorously described. 27,57,59,60 In particular, within the MBPT methods, the Hedin's GW approximation 61 is the state-of-the-art for the computational modeling of photoemission and inverse photoemission processes for solid systems, as well as for the calculation of ionization potentials (IP) and electron affinities (EA) of molecules.…”

GW method and Bethe–Salpeter equation for calculating electronic excitations

“…Electronic screening from Al(111) surface lowers the energy of charge‐transfer excitations in molecular complexes such as benzene–tetracyanoethylene by up to 1 eV from GW + BSE calculations, while TDDFT fails to describe this phenomenon . Electronic level alignment of water and organic molecules on semiconductor substrates was investigated by several groups with GW method, for example by Migani et al for water on TiO 2 (110) surface, by Pham et al for water on Si(111) surface, by Kharche et al for water on GaN and ZnO () surface, by Patrick and Giustino for the chromophore molecule Ru(dcbpyH 2 ) 2 (NCS) 2 and by Verdi et al for the dye molecule (4‐diphenylamino)phenylcyanoacrylic acid on TiO 2 (101) surface . In these molecule–solids interface calculations, the systems are usually large.…”

Electronic structure and phase stability of oxide semiconductors: Performance of dielectric-dependent hybrid functional DFT, benchmarked againstGWband structure calculations and experiments

“…However, GW calculations are much more computationally demanding than DFT-based * carlo.bottani@polimi.it ones, indeed limiting the size of the systems that can be investigated at reasonable cost. Although methodological advances have recently made it possible to treat remarkably complex surface/interface systems at the GW level [5,6], DFT is still widely used for investigating electronic structure features in bulk solids and surfaces, for which in most cases it is able to provide at least a qualitative picture. This can be justified on the basis of the formal similarity between the KS equation and the equation for the poles of the Green's function of many-body perturbation theory, once the xc potential is identified with an approximation of the self-energy operator .…”