XVIII Simpósio Brasileiro de Química Teórica – SBQT 2015
Pirenópolis – GO, 22-25 Novembro de 2015
Electronic Structure and Optical Properties of Diblock Polymers for Solar Cell
Applications
Eliezer Fernando Oliveira a (PG), Francisco Carlos Lavardab (PQ)
a
UNESP - Univ Estadual Paulista, POSMAT - Programa de Pós-Graduação em Ciência e Tecnologia
de Materiais, Bauru, SP, Brazil
b
DF-FC, UNESP - Univ Estadual Paulista, Av. Eng. Luiz Edmundo Carrijo Coube 14-01, 17033-360
Bauru, SP, Brazil.
Keywords: Conducting Polymers, Electronic Structure Calculation, Organic Solar Cells
INTRODUCTION
The search for cheaper sources of renewable
and efficient energy has led the scientific
community to the improvement of organic solar
cells 1. A less commom polymer used as the active
layer is the diblock polymer, which consists of
two types of homopolymers connected to each
other by its ends. Experimental data show that
these types of polymers have an improved
morphology compared to the homopolymer that
constitute the diblock; however, for electronic
structure no improvement was observed 2. In this
work we investigate theoretically the electronic
structure of diblock polymers in order to
understand the electronic structure of these types
of polymers and try to understand why is not
observed improvements in the properties arising
from electronic structure in relation to
homopolymers.
METHODS
We study six diblock polymers built from eight
known polymers: polifenileno vinileno (PPV),
politiofeno (PTh), polipirrol (PPy), polisilole
(PSi), polifosfol (PPh), policiclopentadieno
(PCP),
poli(2-metóxi-5-(2’-etil-hexiloxi)-1,4fenileno vinileno (MEH-PPV) e Poli(3hexiltiofeno) (P3HT). We employ a semiempirical
Hartree-Fock PM6 method for geometry
optimization and Density Functional Theory for
the electronic structure analysis. All calculations
was performed by MOPAC2012, GAMESS and
ORCA programs.
RESULTS AND DISCUSSION
Our results show that the HOMO and LUMO
levels for diblock polymer was always
approximately the HOMO of the homopolymer
that had the highest HOMO and LUMO of the
homopolymer that had the lowest LUMO. The
bandgap of the diblock polymer decreased
compared to homopolymers in which they were
built, but we found these the frontier orbitals were
not extended throughout the main chain (See
Figure 1 for the PCP-block-PTh case). Due to this
fact, there was no HOMO-LUMO optical
transition in diblock polymer.
Figure 1. Kohn-Sham orbitals representation for
a) HOMO e b) LUMO of PCP-block-Pth polymer.
CONCLUSIONS
In general, diblock polymer showed to be a
low bandgap material but with no improvements
regarding to the optical response.
ACKNOWLEDGMENTS
We would like to thank the Brazilian agency
FAPESP (proc. 2012/21983-0 and 2014/20410-1)
for financial support and the resources supplied
by the Center for Scientific Computing
(NCC/GridUNESP) of the São Paulo State
University (UNESP).
H. Zhou, L. Yang, and
Macromolecules 45, 607 (2012).
1
2
W.
You,
D. Gao, J. Hollinger, and D. S. Seferos, ACS
Nano 6, 7114 (2012).