TBranquinho de Queiroz 23mai2025

PCM Seminar - Prof. Thiago Branquinho de Queiroz (Universidade Federal do ABC - Brasil) Vendredi 23 mai 2025, 13h00 - Amphi IPREM

Prof. Thiago Branquinho de Queiroz
Centro de Ciências Naturais e Humanas - Universidade Federal do ABC - Brasil

"Design of small molecular systems and organic-inorganic interfaces for efficient photoinduced charge separation."

Efficient organic photovoltaic (OPV) devices rely on high light absorption and subsequent charge separation within donor-acceptor (D-A) molecular systems. Current limitations in OPV performance include significant exciton and charge recombination losses, restricted charge carrier transport, and device instability due to factors such as electrode oxidation and photodegradation. We have employed accurate density functional theory (DFT) calculations to address these issues in two integrated steps: i. designing novel small donor-acceptor molecules with improved energy level alignment and ii. developing inorganic-organic interfaces to enhance charge extraction. Our "thought device" is composed of a bulk heterojunction of a phenothiazine and S,N-heteroacene derivatives as active layers with an indium tin oxide modified with self assembly monolayer composed of conjugated molecules modified with phosphonic acid as high coupling transparent electrode. In particular, the calculated absorption spectra of the acceptor candidates show an overlap over the whole range of the visible while the candidate donors have a complementary absorption over the red and IR spectrum. Time dependent DFT calculation of one of the promising D-A coupled system shows the lowest excited state, S$_1$, as a charge transfer state at 1.3 eV with a non-negligible oscillator strength of 0.04. Its second excited state, at 1.5 eV, just 0.2 eV above the CT state, is highly optically active, with oscillator strength of 0.90, indicating an efficient population of the CT state with small driving force. From that, we have advanced in the synthesis, structural and (electro)optical characterization of these molecules, their junctions and organic-inorganic interfaces. Thus, in this talk we intend to show how to go from a realistic representation of the molecular systems and organic-inorganic interfaces in theoretical calculations to guide the rational design of more efficient and stable organic photovoltaic devices.

 

Bachelor in physics at the Universidade Federal de Goiás (2007), Ms. and PhD at the Physics Institute of the Universidade de São Paulo (2009 and 2013), and post-doctorate at the Theoretical Physics IV of the University of Bayreuth (2015). 

Has experience in physics of condensed matter and materials science, focusing on design, preparation, and characterization of hybrid luminescent materials through different techniques as solid state nuclear magnetic resonance, optical spectroscopy, and computational methods of quantum calculations, in particular Density Functional Theory. 

Coordinator of the Multiuser Central Facilities of the UFABC/PROPES - Santo André (2018-2022) and since 2015 associate professor at the Center of Natural and Human Science of the Universidade Federal do ABC. His research interests comprise development of organic and hybrid active-media for energy conversion focused on the correlation between structural and electronic properties.