Designing and theoretical study of fluorinated small molecule donor materials for organic solar cells

Usama Mubashar; Afifa Farhat; Rasheed Ahmad Khera; Naseem Iqbal; Rabia Saleem; Javed Iqbal

doi:10.1007/s00894-021-04831-z

Designing and theoretical study of fluorinated small molecule donor materials for organic solar cells

J Mol Model. 2021 Jul 1;27(7):216. doi: 10.1007/s00894-021-04831-z.

Authors

Usama Mubashar¹, Afifa Farhat¹, Rasheed Ahmad Khera², Naseem Iqbal³, Rabia Saleem¹, Javed Iqbal^{4

5}

Affiliations

¹ Department of Chemistry, University of Agriculture, Faisalabad, 38000, Pakistan.
² Department of Chemistry, University of Agriculture, Faisalabad, 38000, Pakistan. rasheedahmadkhera@yahoo.com.
³ US Pakistan Center for Advanced Studies in Energy, National University of Sciences and Technology, Islamabad, 44000, Pakistan.
⁴ Department of Chemistry, University of Agriculture, Faisalabad, 38000, Pakistan. javedkhattak79@gmail.com.
⁵ Punjab Bio-energy Institute, University of Agriculture, Faisalabad, 38000, Pakistan. javedkhattak79@gmail.com.

PMID: 34212225
DOI: 10.1007/s00894-021-04831-z

Abstract

A recently synthesized photoactive donor named fluorinated thienyl-substituted benzodithiophene (DRTB-FT), modified with four novel end capped acceptor molecules, has been investigated through different electrical, quantum, and spectrochemical techniques for its enhanced electro-optical and photovoltaic properties. DRTB-FT was connected to 2-methylenemalononitrile (D-1), 2-methylene-3-oxobutanenitrile (D-2), 2-(2-methylene-3-oxo-2,3-dihydro-1H-inden-1-ylidene) malononitrile (D-3), and 3-methyl-5methylene-2-thioxothiazolidin-4-one (D-4) as terminal acceptor moieties. The architectural D-1 and D-3 molecules owe reduced optical band gap of 2.45 and 2.28 eV benefited from A-D-A configuration and have broaden maximum absorption band (λ_max) at 617 and 602 nm in polar organic solvent (chloroform). Reduced optical band gap sets the ease for enhanced absorption. Reorganization energy of electron (λ_e) of D-3 molecule (0.00397 eV) was smaller among all which disclosed its greater mobility of conducting electrons (ICT). Larger values of dipole moment (μ) of D-1 (5.939 Debye) and D-3 (3.661 Debye) molecules in comparison to R indicated greater solubilities of the targeted molecules. Among the tailored molecules, D-3 showed the lowest binding energy of 0.25 eV in solvent phase and 0.08 eV in gaseous phase. The voltaic strength of the designed molecules was examined with respect to fullerene derivative (PC₆₁BM) which exposed that D-1 is the best choice for achieving higher PCE. TDM (transition density matrix), DOS (density of states) analysis, and binding energies all were estimated at MPW1PW91/6-31G (d, p) level of DFT (density functional theory). All the architecture molecules show reduced band gap and high electron transfer rate due to the lowest reorganization energy (RE) of electron. The results show that there is greater contribution of acceptor and conjugated donor core towards the total absorption into the visible region of the spectrum. When tailored molecules D-1, D-2, D-3, and D-4 were blended with fullerene derivative polymer (PC₆₁BM), they give high values of voltage at zero current level (V_oc) compared to R.

Keywords: Benzodithiophene; Binding energy. TDM; DFT; Reorganization energy.