Tuning opto-electronic properties of alkoxy-induced based electron acceptors in infrared region for high performance organic solar cells

Limitations of fullerene-based acceptors for organic solar cell have driven the scientific community to design and synthesize non-fullerene acceptors. In this regard, we have designed four new molecules designated here S1-54 containing Alkoxy-Induced Naphtho-dithiophene donor unit and 2-(5,6-difluoro-2-methylene-3-xo-2,3-dihydrinden-1-ylidene)malonoitrile acceptor moiety attached with different bridge units. The electronic and optical properties of the designed molecules S1-S4 are compared with the recently reported reference molecule R. The bridge units are, thiophene (S1), 2-fluorothiophene (S2), 2-(thiophe-2-yl)thiophene (S3) and 2-(4-fluorothiophen-2-yl)thiophene (S4). The designed molecule S3 shows absorption maximum in near infra-red (NIR) region at 830.0 nm and 910.6 nm in gas phase and chloroform solvent, respectively. The energy gaps of designed molecules are lower than that of the reference R, which reveal high charge transfer for the designed molecules. Among all, S3 has the lowest energy gap (1.68 eV). Open circuit voltages (V-oc) calculation are performed with well-known PTB7-Th donor. V-oc, of all the molecules are higher than R where the maximum V-oc of 1.92 V is calculated for S2. Low reorganization energies of our designed molecule reflect high charge transfer rate with respect to R. Among all designed molecules, S3 has the highest electron mobility. (C) 2019 Elsevier B.V. All rights reserved.