Quantum Chemical Design of Near-Infrared Sensitive Fused Ring Electron
Acceptors Containing Selenopheneas π-bridge for High-Performance Organic
Solar Cells
Abstract
End-capped acceptor modification of fused-ring electron acceptors
(FREAs) is an attractive strategy to boost the optoelectronic and
photovoltaic properties of the materials. FREAsare proved beneficial due
to their tremendous applications in organic solar cells (OSCs). Among
fused-ring electronic species, small fullerene-free FREAs have already
been drawn more attention due to their near-infrared sensitivity and
constantly increasing efficiencies. Therefore, we have designed six new
FREAs (K1-K6) having selenophene as π-bridge in between the central
alkylated indaceno[1,2-b:5,6b]dithiophene (IDT) unit after the
incorporations of various end-capped acceptors on to the recently
synthesized IDT2SeC2C4-4F molecule. Structural-property relationship,
photophysical and photovoltaic properties of newly designed molecules
are studied with the help of density functional theory (DFT) and
time-dependent-density functional theory (TD-DFT). Certain critical
specifications like frontier molecular orbital (FMOs) alignment, the
density of states (DOS), absorption maxima, excitation energy, binding
energy (B.E) along with transition density matrix (TDM), and the
specifically estimated re-organizational energy values of electron and
hole and the open circuit voltages of newly designed molecules are
computed and compared with reference molecule. Generally, a red-shifting
absorption behavior of FREAs is considered the most important reason for
their high efficiencies in OSCs. Our novel designed molecules exhibit
redshift in the absorption spectrum. Similarly, low excitation and
binding energies of designed molecules offer improved power conversion
efficiencies (PCE) with the highest possible charge photo-current
density (Jsc) in OSCs devices. Furthermore, the study of the PTB7-Th/K1
complex is also done in order to examine charge transfer between within
complex. By introducing the efficient end-capped acceptor moieties in
reference molecule, enhancement in charge mobilities is noted. The large
open-circuit voltage, low reorganizational energies, narrower HOMO-LUMO
energy gap, lower binding and excitation energies, and highly
red-shifting in absorption phenomenon indicates an efficient designing
of molecules that could be best fitted for high-efficiency OSCs.
Finally, theorized molecules are much superior related to their
photovoltaic and electronic properties and thus are recommended to
experimentalists for their synthesis and out-looking future developments
of highly efficient solar cell devices.