Effects of orientation at the phthalocyanine–CdSe interface on the electron transfer characteristics

Abstract

A phthalocyanine molecule adsorbed on the (101[combining macron]0) surface of wurtzite CdSe is theoretically modeled by the DFT method. We have found that a linker does not affect substantially the redox properties of phthalocyanine, while saturation of the macrocycle with peripheral substituent groups causes a downward shift in the energy position of its frontier orbitals that can hinder electron injection to the CdSe surface. Tilting of the phthalocyanine molecule relative to the surface also leads to the lowering of its molecular electronic levels relative to the bands of CdSe. At a tilting angle of 30°, the LUMO level of the dye appears to be lower than the conduction band minimum of cadmium selenide, which makes the electron transfer to its hybridized surface unfavorable. By contrast, the HOMO level of the phenylbutyric acid linker provides a suitable intermediate channel for the hole transfer from the valence band of CdSe to the phthalocyanine that points to the possible acceptor behavior of the phthalocyanine molecule in its hybrids with CdSe nanostructures.

Photoreactions of Macrocyclic Dyes on (1010) Wurtzite Surface – Interplay Between Conformation and Electronic Effects

“…Earlier, we have found that the saturation of Pc with eight phenylbutyric acid linkers attached to the macrocycle via an oxygen atom (as in compound 5, Fig. 1) causes a significant downward shift (0.1-0.3 eV) in frontier orbital energies [8]. The linker can also play a substantial role in electron transfer by providing the through-bond electron tunneling mediated by a bridge.…”

“…Ones of the most developed and studied hybrids based on these nanostructures are their conjugation with macrocyclic dyes such as porphyrin and phthalocyanine (Pc) derivatives [7][8][9]. It should be noted, however, that hybrids with phthalocyanines are relatively unexplored due to the moderate energy conversion efficiencies achieved so far for Pcbased dye sensitized solar cells.…”

Photoinduced Charge Separation in Semiconductor‐Quantum‐Dot/Organic‐Molecule Hybrids

“…A few noticeable studies were published with the aim to model the electronic interactions in the QD–dye molecule hybrids and to understand the physics of the charge‐transfer process, including a review by Kilina et al . Some efforts were undertaken to model systems studied experimentally, QD–C 60 , QD–AQ and QD–Pc hybrids. However, the level of theoretical understanding and modelling is not yet sufficient to predict the outcome of putting together a new QD–molecular dye pair.…”