Light and Molecules

Mario Barbatti's Research Group

Organic photovoltaics

Looking at the future: organic electronics

Donor-acceptor organic heterojunctions (DA-OHJ) have been extensively explored for photodevices. They are promising materials due to their potential low-cost and plastic properties.

The search for new DA-OHJ goes through the cumbersome process of designing, synthesizing and testing new molecular complexes, heuristically improving certain properties over the previous generation of complexes.

Computational simulations may be a valuable tool for this search, as they may help to

  • Explain the basic photophysical processes;
  • Pre-screen hypothetical molecular complexes prior the synthesis.

To achieve these aims, however, it is needed to

  • Assess the quality of the computational predictions;
  • Develop new research protocols to deal with such complex systems;
  • Connect atomistic simulations to mesoscopic simulations.

Our research group has systematically tackling each of these points in a long term project.

Photophysics of a D-A-OHJ

Organic photovoltaic operation

Conceptually, the operation of a DA-OHJ is based on the 5 steps above.

How accurate is this picture? How does exactly each step take place?
These are questions that we are addressing now.

We showed, for instance that in certain cases, charge recombination follows a non-Marcus regime (Ref).

Automatic State Classification

Based on a CI approximation for the excited-state densities, states of a D-A complex can be classified as localized, delocalized or charge-transfer (Ref).

State classification

We have applied this approach to analyze the electronic structure of thiophene oligomers (Ref) and squaraine dies (Ref) in complexes with fullerenes.

Electronic structure of P3TH-PCBM hetero dimer.
Electronic structure of P3TH-PCBM hetero dimer. Blue: LOC(PCBM); Cyan: LOC(P3TH); Red: CT(P3TH-PCBM). Starts indicate bright states.


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