Role of Iodo-Substituted Subphthalocyanine (Subpcs) π-conjugated aromatic N-fused di-Iminoisonidole units on the performance of non-fullerene small organic solar cells

[Display omitted] Estimated open circuit voltages of designed ADA type donor materials for enhanced PCEs. •Analyzing the effect of Iodo-Substituted Subphthalocyanine (Subpcs) π-conjugated aromatic N-fused di-Iminoisonidole units.•Changing acceptor moieties with different electron withdrawing groups for increasing absorption strength.•Computed binding energy and transition density matrix.•Designed molecule shows strong open circuit voltages than reference molecule.•Large solubility strength in polar organic solvents for further construction of solar cells devices. Four acceptor–donor-acceptor (A-D-A) type of iodo-substituted subphthalocyanine (Subpcs) donor molecules have been designed with π-conjugated rigid tetrahedral geometry in which aromatic ring of three units combined around boron atom bearing a macrocycle core with perpendicular axial ligand. Subphthalocyanine are substituted with four different acceptor moieties (Z)-methyl 3-cyanobut-2-enoate (M1), (Z)-5-ethylidene-3-methyl-2-thioxothiazocidin-4-one (M2), 2-(2-methylene-3-oxo-2,3-dihydroinden-1-ylidene) malononitrile (M3), m-ethyl 2(5-methylene-4-oxo-2-thioxothiazolidin-3-yl) acetate (M4). The expansion of pyrrole ring is increased by benzoannulation of axial group which attached to enhance their HOMO energy levels. The optoelectronic properties of designed ADA subphthalocyanine molecules have been computed with B3LYP/LanL2DZ combination of density functional theory. The energy gap (EH-L) of reference molecule is 2.71 eV. The M2 exhibited the narrow band gap (2.15 eV) among other designed donor molecules due to their strong electron-withdrawing group. This computational study and results showed that these designed molecules have large influence on increasing the performance of organic solar cells as small organic materials.