TY - JOUR
T1 - Assessing the effects of increasing conjugation length on exciton diffusion: from small molecules to the polymeric limit
AU - de Sousa, Leonardo Evaristo
AU - de Paiva, Laura Simonassi Raso
AU - da Silva Filho, Demetrio Antonio
AU - Sini, Gjergji
AU - de Oliveira Neto, Pedro Henrique
PY - 2021
Y1 - 2021
N2 - Organic solar cells (OSC) generally contain long-chain pi-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 Forster 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.
AB - Organic solar cells (OSC) generally contain long-chain pi-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 Forster 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.
U2 - 10.1039/d1cp01263k
DO - 10.1039/d1cp01263k
M3 - Journal article
C2 - 34268543
SN - 1463-9076
VL - 23
SP - 15635
EP - 15644
JO - Physical Chemistry Chemical Physics
JF - Physical Chemistry Chemical Physics
IS - 29
ER -