Título:	Assessing the effects of increasing conjugation length on exciton diffusion : from small molecules to the polymeric limit
Autor(es):	Sousa, Leonardo Evaristo de Paiva, Laura Simonassi Raso de Silva Filho, Demétrio Antônio da Sini, Gjergji Oliveira Neto, Pedro Henrique de
ORCID:	https://orcid.org/0000-0002-5880-5325 https://orcid.org/0000-0002-7103-4780 https://orcid.org/0000-0003-2548-8260 https://orcid.org/0000-0002-8336-7718
Assunto:	Célula solar orgânica Eletrônica orgânica Éxciton
Data de publicação:	2021
Editora:	Royal Society of Chemistry
Referência:	SOUSA, Leonardo Evaristo de et al. Assessing the effects of increasing conjugation length on exciton diffusion: from small molecules to the polymeric limit. Physical Chemistry Chemical Physics, v. 23, n. 9, p. 15635–15644, 2021. DOI 10.1039/d1cp01263k. Disponível em: https://pubs.rsc.org/en/content/articlelanding/2021/CP/D1CP01263K. Acesso em: 05 ago. 2022.
Abstract:	Organic solar cells (OSC) generally contain long-chain p-conjugated polymers as donor materials, but, more recently, small-molecule donors have also attracted considerable attention. The nature of these compounds is of crucial importance concerning the various processes that determine device performance, among which singlet exciton diffusion is one of the most relevant. The efficiency of the diffusion mechanism depends on several aspects, from system morphology to electronic structure properties, which vary importantly with molecular size. In this work, we investigated the effects of conjugation length on the exciton diffusion length through electronic structure calculations and an exciton diffusion model. By applying extrapolation procedures to thiophene and phenylene vinylene oligomer series, we investigate their electronic and optical properties from the small-molecule point of view to the polymeric limit. Several properties are calculated as a function of oligomer size, including transition energies, absorption and emission spectra, reorganization energies, exciton coupling and Förster radii. Finally, an exciton diffusion model is used to estimate diffusion lengths as a function of oligomer size and for the polymeric limit showing agreement with experimental data. Results also show that longer conjugation lengths correlate with longer exciton diffusion lengths in spite of also being associated with shorter exciton lifetimes.
DOI:	https://doi.org/10.5252/10.1039/d1cp01263k
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