TY - JOUR
T1 - Intrinsic Properties of Two Benzodithiophene-Based Donor-Acceptor Copolymers Used in Organic Solar Cells
T2 - A Quantum-Chemical Approach
AU - Kastinen, Tuuva
AU - Niskanen, Mika
AU - Risko, Chad
AU - Cramariuc, Oana
AU - Hukka, Terttu I.
N1 - Publisher Copyright:
© 2016 American Chemical Society.
PY - 2016/2/25
Y1 - 2016/2/25
N2 - Conjugated donor-acceptor (D-A) copolymers show tremendous promise as active components in thin-film organic bulk heterojunction solar cells and transistors, as appropriate combinations of D-A units enable regulation of the intrinsic electronic and optical properties of the polymer. Here, the structural, electronic, and optical properties of two D-A copolymers that make use of thieno[3,4-c]pyrrole-4,6-dione as the acceptor and differ by their donor unit - benzo[1,2-b:4,5-b′]dithiophene (BDT) vs the ladder-type heptacyclic benzodi(cyclopentadithiophene) - are compared using density functional theory methods. Our calculations predict some general similarities, although the differences in the donor structures lead also to clear differences. The extended conjugation of the stiff ladder-type donor destabilizes both the highest occupied and lowest unoccupied molecular orbital energies of the ladder copolymer and results in smaller gap energies compared to its smaller counterpart. However, more significant charge transfer nature is predicted for the smaller BDT-based copolymer by natural transition orbitals than for the ladder copolymer. That is, the influence of the acceptor on the copolymer properties is "diluted" to some extent by the already extended conjugation of the ladder-type donor. Thus, the use of stronger acceptor units with the ladder-type donors would benefit the future design of new D-A copolymers. (Chemical Equation Presented).
AB - Conjugated donor-acceptor (D-A) copolymers show tremendous promise as active components in thin-film organic bulk heterojunction solar cells and transistors, as appropriate combinations of D-A units enable regulation of the intrinsic electronic and optical properties of the polymer. Here, the structural, electronic, and optical properties of two D-A copolymers that make use of thieno[3,4-c]pyrrole-4,6-dione as the acceptor and differ by their donor unit - benzo[1,2-b:4,5-b′]dithiophene (BDT) vs the ladder-type heptacyclic benzodi(cyclopentadithiophene) - are compared using density functional theory methods. Our calculations predict some general similarities, although the differences in the donor structures lead also to clear differences. The extended conjugation of the stiff ladder-type donor destabilizes both the highest occupied and lowest unoccupied molecular orbital energies of the ladder copolymer and results in smaller gap energies compared to its smaller counterpart. However, more significant charge transfer nature is predicted for the smaller BDT-based copolymer by natural transition orbitals than for the ladder copolymer. That is, the influence of the acceptor on the copolymer properties is "diluted" to some extent by the already extended conjugation of the ladder-type donor. Thus, the use of stronger acceptor units with the ladder-type donors would benefit the future design of new D-A copolymers. (Chemical Equation Presented).
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U2 - 10.1021/acs.jpca.5b08465
DO - 10.1021/acs.jpca.5b08465
M3 - Article
AN - SCOPUS:84959420776
SN - 1089-5639
VL - 120
SP - 1051
EP - 1064
JO - Journal of Physical Chemistry A
JF - Journal of Physical Chemistry A
IS - 7
ER -