30 September 2022

Friday Materials Science Colloquia (#2)

Seminar

Friday September 30th, 2022
12 p.m.
Seminar room, U5 Building – via Roberto Cozzi 55, Milano

 

Lecturer: Alessandro Minotto

 

Title: Singlet exciton fission in molecular thin films for enhanced photovoltaics

 

Abstract: The formation of spin-triplet excitons is conventionally considered detrimental for organic optoelectronics. Yet, in the field of organic light-emitting diodes, researchers subverted this wisdom by engineering highly efficient triplet-leveraging emitters[1]. Equally strikingly, solar cells incorporating acenes and other classes of molecular semiconductors exhibiting singlet fission (SF), i.e. an exciton multiplication process whereby one singlet is converted to two triplet excitons, recently showed quantum efficiencies >100%[2]. However, these recent findings also demonstrate that, for the successful exploitation of triplets generated via SF, control over molecular packing is required. In this presentation, I will discuss the opportunities offered by the growth of SF-active films via organic molecular beam epitaxy (OMBE),[3,4] a technique which satisfies the above requirement, as well as show some preliminary results from our group.

 

References:

[1] A. Zampetti et al., Adv. Funct. Mater. 2019, 29, 1807623.

[2] B. Daiber et al., ACS Energy Lett. 2021, 6, 2800.

[3] S. Trabattoni et al., Adv. Mater. Interfaces 2015, 2, 1500423.

[4] L. Raimondo et al., Adv. Mater. Interfaces 2017, 4, 1700670.

 

 

Lecturer: Giovanni Di Liberto

 

Title: Modeling Heterogeneous Catalysts: From Extended Semiconductors Interfaces to Embedded Metal Single Atoms

 

Abstract: Heterogeneous catalysis plays a fundamental role in materials’ science[1]. Semiconductor’ heterojunctions and Single-Atom Catalysts (SACs) are two relevant families in this respect. Computational chemistry can give a contribution to help the design of active materials and to understand the mechanism of chemical reactions of interest.

We will first discuss the modeling of heterojunctions for photo-catalysis applications, showing the role played by the junction in determining the expected activity[2-4]. Later, we will look at Single-Atom Catalysts for photo- or electro-catalytic applications such as water splitting and CO2 reduction. We will highlight the analogy between SACs and coordination chemistry compounds, opening the way toward the generation of “unconventional” intermediates that may affect the activity in Hydrogen and Oxygen Evolution Reactions[5,6]. We will also show the need for extending the existing computational models for the specific field of SACs.

 

References:

[1] Z Wang et al., Chem. Soc. Rev. 2019, 48, 2109.

[2] G. Di Liberto et al., J. Phys. Chem. Lett. 2019, 10, 2372; G. Di Liberto et al., Adv. Funct. Mater. 2021, 31, 2009472.

[3] G. Di Liberto et al., Chem.–Eur. J. 2021, 27, 13306.

[4] G. Di Liberto et al., Nat. Commun., Just Accepted.

[5] G. Di Liberto et al., J. Am. Chem. Soc., 2021, 143, 20431; G. Di Liberto et al., ACS Catal. 2022, 12, 5846-5856.

[6] L.A. Cipriano et al., "Superoxo and Peroxo Complexes on Single-Atom Catalysts: Impact on the Oxygen Evolution Reaction", ACS Catal, In press.