Regensburg 2013 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 17: Focussed Session: Frontiers of Electronic Structure Theory II (jointly with HL and TT)

O 17.8: Vortrag

Montag, 11. März 2013, 17:45–18:00, H36

Electronic properties of isolated and supported organic dyes modeled through the GW method — •Paolo Umari¹, Filippo De Angelis², Luigi Giacomazzi³, Mariachiara Pastore², and Stefano Baroni³ — ¹Dipartimento di Fisica e Astronomia, Università di Padova, Italy — ²Istituto CNR di Scienze e Tecnologie Molecolari, Perugia, Italy — ³Scuola Internazionale Superiore di Studi Avanzati (SISSA), Trieste, Italy

The first-principles GW method is used for investigating the electronic levels of isolated and supported dyes for electrochemical solar cells. We consider a set of all-organic dyes, (L0,L2,L3,L4) exhibiting the same donor and anchor groups. First, we calculate the energy levels in the limit of isolated molecules obtaining nice agreement with available experimental photoelectron spectra. Then, we consider the L0 and the L2 dyes while adsorbed on the anatase TiO₂ (101) surface. Also in this case we find good agreement when comparing with available experimental photoelectron spectra. We find that the HOMO -LUMO gap of the dye is reduced with respect to the isolated molecule and that the HOMO level is slightly shifted towards higher energies due to image charge effects. This permits us to derive a simple model for obtaining approximate GW energy levels for the HOMO and the LUMO of the adsorbed molecule and for the valence band maximum and the conduction band minimum of the substrate performing just one complete GW calculation of the isolated molecule and one of the bulk TiO₂ combined with a calculation at the DFT level of the adsorbed molecule complex. In this way, we can investigate larger, more realistic, model structures.