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A systematic analysis of excitonic properties to seek optimal singlet fission: the BN-substitution patterns in tetracene

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journal contribution
posted on 27.04.2020, 09:16 by Max Pinheiro Jr, Francisco BC Machado, Felix PlasserFelix Plasser, Adelia Aquino, Hans Lischka

The development of efficient organic-based photovoltaic devices is a vibrant area of research with the potential of providing a cheap source of sustainable energy to society. The attainable power conversion efficiencies could be strongly enhanced via the singlet fission (SF) mechanism, a quantum mechanical phenomenon that potentially doubles the number of electron-hole pairs in a photoexcitation process by splitting a high energy singlet into two triplets. Biradicaloid molecules are particularly appealing for SF applications due to the possibility of controlling the balance between open-shell and closed-shell resonance structures via chemical modifications, which open new opportunities to fine tune the singlet and triplet excitation energies, and thus maximize the SF efficiency. Recently, we have shown that doping acenes with boron (B) or nitrogen (N) atoms leads to a large modulation in its biradicaloid nature at the ground-state. Herein, this previous study is extended to the case of asymmetric substitutions by introducing a BN-pair in a tetracene molecule to form azaborine analogues of acenes. The consequences of the chemical doping on the excitonic properties of tetracene is investigated through high-level multireference calculations. From a pool of 60 proposed BN-tetracene chromophores, we identify 15 new promising candidates for SF as they satisfy the energy level matching conditions involving the low-lying singlet and triplet states of a monomer. Still, some of these compounds show good chemical stability as evidenced by their modest biradical character. These results are interpreted in terms of aromaticity changes, charge transfer effects and exciton properties. More generally, this study shows how the energetics of singlet fission materials can be dramatically altered by using fairly simple chemical substitutions and provides detailed insight into the underlying relationships between the molecular structure, the electronic structure, and the excited state energies.

Funding

Brazilian agencies Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) under Projects Nos. 307136/2019-1, 404337/2016-3

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) under Projects Process No. 2019/25105-6

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) under Project No. 88882.161963/2014-01

History

School

  • Science

Department

  • Chemistry

Published in

Journal of Materials Chemistry C

Volume

8

Issue

23

Pages

7793 - 7804

Publisher

Royal Society of Chemistry (RSC)

Version

AM (Accepted Manuscript)

Rights holder

© Royal Society of Chemistry

Publisher statement

This paper was accepted for publication in the journal Journal of Materials Chemistry C and the definitive published version is available at https://doi.org/10.1039/c9tc06581d

Acceptance date

20/04/2020

Publication date

2020-04-21

Copyright date

2020

ISSN

2050-7526

eISSN

2050-7534

Language

en

Depositor

Dr Felix Plasser Deposit date: 24 April 2020

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