cm9b00056_si_001.pdf (618.86 kB)
Tuning Charge Generation Process of Rylene Imide-Based Solar Cells via Chalcogen-Atom-Annulation
journal contribution
posted on 2019-04-22, 00:00 authored by Ningning Liang, Xixiang Zhu, Zhong Zheng, Dong Meng, Guogang Liu, Jianqi Zhang, Sunsun Li, Yan Li, Jianhui Hou, Bin Hu, Zhaohui WangA series
of high-performance organic semiconductors, which are
modulated by introducing heteroatoms to rationally control molecular
packing and charge carrier transport, have been successfully reported.
However, a fundamental physical understanding of the impact of chalcogen
atoms on intermolecular interactions between donors and acceptors
as well as photophysical process in photovoltaic cells is still lagging.
Herein, a detailed investigation on rylene imide-based solar cells
is carried out to reveal the role of chalcogen atoms in controlling
intermolecular interactions, molecular orientation in bulk and at
the donor–acceptor interface, and polaron-pair dissociation.
Compared to their Se-atom-free assisted counterparts, poly{[4,8-bis[5-(2-ethylhexyl)-4-fluoro-2-thienyl]benzo[1,2-b:4,5-b′]dithiophene2,6-diyl]-alt-[2,5-thiophenediyl[5,7-bis(2-ethylhexyl)-4,8-dioxo-4H,8H-benzo[1,2-c:4,5-c′]dithiophene-1,3-diyl]]} (PBDB-TF): selenium-annulated
triperylene hexaimide (TPH-Se) bulk heterojunctions preserve face-on
orientation and possess smaller domain size, which are partially attributed
to the Se···O van der Waals contacts between the acceptor
and polymer chain. This feature enables PBDB-TF:TPH-Se interfaces
with enhanced π-orbital overlap, improved charge transfer, a
narrowed charge-transfer band, and suppressed polaron-pair binding
energy. Consequently, all of the Se-containing solar cells investigated
in this manuscript exhibit higher short-circuit current densities
and conversion efficiencies than those in Se-atom-free devices. Our
results reveal an important molecular design strategy for high-performance
rylene imide-based acceptors: efficiently improving the electronic
interactions at the D–A interface to increase polaron-pair
dissociation and suppress geminate recombination.