Light and Molecules

Mario Barbatti's Research Group

Organic photodevices

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.

In a series of investigations, we have learned:

 

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.