Applying
Thienyl Side Chains and Different π‑Bridge to Aromatic
Side-Chain Substituted Indacenodithiophene-Based Small Molecule Donors
for High-Performance Organic Solar Cells
posted on 2017-05-23, 00:00authored byJin-Liang Wang, Kai-Kai Liu, Sha Liu, Feng Liu, Hong-Bin Wu, Yong Cao, Thomas P. Russell
A pair
of linear tetrafluorinated small molecular donors, named as ThIDTTh4F and ThIDTSe4F, which are with tetrathienyl-substituted
IDT as electron-rich central core, electron-deficient difluorobenzothiadiazole
as acceptor units, and donor end-capping groups, but having differences
in the π-bridge (thiophene and selenophene), were successfully
synthesized and evaluated as donor materials in organic solar cells.
Such π-bridge and core units in these small molecules play a
decisive role in the formation of the nanoscale separation of the
blend films, which were systematically investigated through absorption
spectra, grazing incidence X-ray diffraction pattern, transmission
electron microscopy images, resonant soft X-ray scattering profiles,
and charge mobility measurement. The ThIDTSe4F (with
selenophene π-bridge)-based device exhibited superior performance
than devices based on ThIDTh4F (with thiophene π-bridge)
after post annealing treatment owing to optimized film morphology
and improved charge transport. Power conversion efficiency of 7.31%
and fill factor of ∼0.70 were obtained by using a blend of ThIDTSe4F and PC71BM with thermal annealing and solvent vapor annealing treatments,
which is the highest PCE from aromatic side-chain substituted IDT-based
small molecular solar cells. The scope of this study is to reveal
the structure–property relationship of the aromatic side-chain
substituted IDT-based donor materials as a function of π-bridge
and the post annealing conditions.