Novel Donor-Electret-Acceptor Framework for Higher Charge Transfer and Distance of Charge Transfer through Dipole Engineering
Journal
Journal of Physical Chemistry C
Journal Volume
125
Journal Issue
37
Pages
20219-20229
Date Issued
2021
Author(s)
Abstract
Solar cells try to mimic the natural process of photosynthesis to convert light energy into electrical energy. Long-range electron transfers occur rapidly between donor-acceptor pairs within the protein matrix. However, protein-based moieties are not suited for electronic applications. The widely employed donor-(bridge)n-acceptor (DBnA; n ? 1) framework typically fails to effectively transfer the charge over longer distances, leading to larger exciton binding energies and lower power conversion efficiencies in organic solar cells. By modifying the dipole neutral bridge into an electret, we propose a donor-electretn-acceptor (DEnA; n ? 1) model, which addresses the limitations of the conventional donor-bridge-acceptor (DBA) architecture. We design a novel electret based on an aromatic-5-membered ring (A5R) substituted with polar groups in a stereoregular fashion. Due to the peculiar symmetry offered by the A5R and the asymmetry achieved through the regioregular substitution of polar groups, a co-directional dipole is induced along the electret backbone. Exploiting this unique behavior and orienting the dipole direction of the electret opposite to the donor-acceptor duo in the donor-electret-acceptor (DEA) framework, higher magnitudes of charge transfer (qCT) and distance of charge transfer (DCT) are realized. This novel design offers the following: (1) Higher qCT and DCT are achieved, which overcomes the inherent length dependency of DBAs with increasing chain length. (2) DCT over ?12 ? and beyond is possible with the proposed DEA architecture, which can compete with the natural protein helix in efficient electron transfer and exciton dissociation. (3) The electret allows us to tune the ground-state (GS) dipole without compromising on higher qCT and DCT properties; the lower GS dipole enables the solubility of DEAs in mild solvents. (4) Higher degrees of freedom in the substitution patterns provided by the electret allow us to alter not only qCT and DCT but also other electronic and optical properties including lowest unoccupied molecular orbital-highest occupied molecular orbital gaps, optical gaps, dipoles, oscillator strengths, and so on. (5) A new window in exploiting the substitution patterns provided by the electret to design novel materials is opened, which have potential applications in diverse areas. Our density functional theory/time-dependent density functional theory studies employing optimally tuned range-separated hybrids predict accurate optical properties against the experimental results. ? 2021 American Chemical Society.
Subjects
Binding energy
Degrees of freedom (mechanics)
Density functional theory
Electron transitions
Excitons
Ground state
Molecular orbitals
Optical properties
Organic solar cells
Proteins
Donor-acceptor pairs
Electrical energy
Electronics applications
High charges
Light energy
Long-range electron transfer
Natural process
Polar groups
Protein matrix
Substitution patterns
Charge transfer
SDGs
Type
journal article