Non-fullerene small acceptor molecules have gained significant attention for application in organic solar cells owing to their advantages over fullerene based acceptors. Efforts are continuously being made to design novel acceptors with greater efficiencies. Here, optoelectronic properties of four novel acceptor–donor–acceptor (A–D–A) type small molecules (A1, A2, A3 and A4) were studied for their applications in organic solar cells. These molecules contain an indacenodithiophene central core unit joined to different end capped acceptors through a monofluoro substituted benzothiadiazole (FBT) donor acceptor (DA) bridge. The different end capped acceptor groups are; 2-2(2-ethylidene-5,6-difluoro-3-oxo-2,3-dihydroinden-1-ylidene)malononitrile (A1), 2-2(2-ethylidene-3-oxo-2,3-dihydroinden-1-ylidene)malononitrile (A2), 2-(5-ethylidene-6-oxo-5,6-dihydrocyclopenta-b-thiophene-4-ylidene)malononitrile (A3), and 2-2(2-ethylidene-5,6-dicyano-3-oxo-2,3-dihydroinden-1-ylidene)malononitrile (A4). The calculated optoelectronic properties of the designed molecules were compared with a well-known reference compound R, which was recently synthesized and reported as being an excellent A–D–A type acceptor molecule. All designed molecules showed the appropriate frontier molecular orbital diagram for a charge transfer. A4 shows the highest absorption maximum (λ_max) of 858.6 nm (in chloroform solvent), which was attributed to the strong electron withdrawing end-capped acceptor group. Among all of the designed molecules, A3 exhibits the highest open circuit voltages (V_oc) which was (1.84 V) with PTB7-Th and (1.76 V) with the P3HT donor polymer. Owing to a lower value of λ_e with respect to λ_h, the designed molecules demonstrated superior electron mobilities when compared with reference R. Among all of the molecules, A4 shows the highest electron mobility owing to the lower value of λ_e compared to R.

This quantum mechanical study focuses on the designing of twelve (MPAM1–MPAM12) bithieno thiophene (BTTI) central core-based small molecules to explore optoelectronic properties as donor candidates for organic solar cells (OSCs) and hole transport materials (HTMs) accompanied by enhanced charge mobility for perovskite solar cells (PSCs). MPAM1–MPAM6 have been designed by the substitution of thiophene-bridged end-capped acceptors on both side terminals of reference (MPAR). MPAM7–MPAM12 are tailored by adopting the same tactic on one side terminal only. MPW1PW91/6-311G (d,p) has been employed for all computational simulations. MPAM12 revealed the highest λ_max at 639 nm in dichloromethane (DCM) solvent with the lowest E_g of 1.78 eV and dipole moment (20.74 D) in the solvent phase, showing excellent miscibility as compared to the reference. All designed chromophores (MPAM1–MPAM12) demonstrated higher estimated V_OC and power conversion efficiency (PCE) when compared to MPAR, suggesting their prominent operational efficiency. Among all, MPAM4 manifested the highest PCE (47.86%). MPAM2 portrayed the highest electron mobility (0.0041573 eV) and MPAM3 exhibited the highest hole mobility (0.0047178 eV). The outcomes highlight the adequacy of the planned strategies, paving a new route for the development of small-molecule HTMs for PSCs and donor contributors for OSCs.