Designing of benzodithiophene (BDT) based non-fullerene small molecules with favorable optoelectronic properties for proficient organic solar cells

Abstract

To extinguish the thirst of extraordinary tailback in the stock of energy and to jack up the operational effectiveness of organic solar cells, 5 new donor molecules namely BDTM1, BDTM2, BDTM3, BDTM4, BDTM5 have been designed by the structural tailoring of the already experimentally synthesized POBDT-4Cl. POBDT-4Cl is taken as a reference designated as BDTR. All the designed chromophores constitute benzodithiophene as donor and thiophene bridged end-capped (3-methyl-5-methylene-2-thioxothiazolidin-4-one) BDTM1, (2-methylenemalononitrile) BDTM2, (methyl 2-cyanoacrylate) BDTM3, (2-(3-methyl-5-methylene-4-oxothiazolidin-2-ylidene)malononitrile) BDTM4, (4-(5-methylthiophen-2-yl)benzo[c][1,2,5]thiadiazole) BDTM5 acceptor groups. Influence of different terminal acceptor moieties on the molecular orbitals, density of states (DOS), maximum absorption (λmax), energy required for the generation of electron and hole carrier, transition density matrix (TDM), dipole moment, reorganization energy (RE), and open-circuit voltage (VOC) has been inquired via density-functional theory (DFT) and time-dependent density functional theory (TDDFT) methodology using B3LYP/6-31G (d,p) and these afore-mentioned features of newly devised molecules have been compared with the reference (BDTR). Among all newly designed molecules (BDTM1-BDTM5), BDTM1 exhibited the highest λmax value of 725 nm. BDTM3, BDTM4, and BDTM5 have displayed the highest dipole moment than the reference (BDTR). Cation (hole) transport rate of BDTM5 (0.00578 eV) and BDTM2 (0.00632 eV) has been explored lower than BDTR (0.00662 eV). Similarly, BDTM5 has displayed lower anion (electron) transport rate (0.00578 eV) relative to BDTR (0.00603 eV). Among all designed molecules, BDTM5 has expressed formidable and unique results accompanied by the lowest band gap (1.90 eV), comparable λmax (720 nm), and VOC. All newly constructed molecules have exposed enhanced VOC. Briefly, the thiophene bridged end-capped acceptor modification approach has been demonstrated compelling in providing the door to plan profoundly effective photovoltaic materials accompanied by exquisite optoelectronic parameters.