Sample application: coupled organic - inorganic systems - theoretical design -
Fundamental features of the interaction of phthalocyanines (Pcs) with semiconductors are accessed through first-principle simulations. This study shed light on the more general problem of organic-inorganic coupling and show that effective coupling can be achieved by a careful choice of the Pc-substrate system and semiconductor doping.
The problem: Phthalocyanine is a metallo-organic macrocyclic complex (MOMC), containing a metal in its center and showing transport and non linear optical properties that could be exploited in Pc-semiconductor junctions to design new opto-electronic devices. Unfortunately, the weakness of the coupling between Pcs and semiconductors is an obstacle to technological applications. Using Quantum Espresso to investigate various Pc-semiconductor systems, a strategy has been devised to achieve an effective coupling.
Results: · An effective coupling is obtained for a phthalocyanine molecule that contains oxygen and Titanium (OTi) and is adsorbed on TiO2 anatase surface.
· A universal alignment of the Pc electronic levels to the semiconductor band gap.
· The (OTi-Pc)-TiO2 system has been designed exploiting:
- the chemical affinity of the Pc central group with surface atoms to create a bond;
- a suitable doping of the inorganic semiconductors to induce a molecule-surface charge transfer through that chemical bridge.
Tools: PWSCF code, available within Quantum Espresso package for electronic structure calculations.
References: · G. Mattioli, F. Filippone, P. Giannozzi, R. Caminiti, and A. Amore Bonapasta: Theoretical design of coupled organic-inorganic systems. To be published.