Improvement of short circuit current density by intermolecular interaction between polymer backbones for polymer solar cells

Effect of tailoring π-linkers with extended conjugation on the SJ-IC molecule for achieving high VOC and improved charge mobility towards enhanced photovoltaic applications

The problem of low efficiency of organic solar cells can be solved by improving the charge mobility and open circuit voltage of these cells. The current research aims to present the role of π-linkers, having extended conjugation, between the donor and acceptor moieties of indacenodithiophene core-based A-π-D-π-A type SJ-IC molecule to improve the photovoltaic performance of pre-existing SJ-IC. Several crucial photovoltaic parameters of SJ-IC and seven newly proposed molecules were studied using density functional theory. Surprisingly, this theoretical framework manifested that the tailoring of SJ-IC by replacing its π-linker with linkers having extended π-conjugation gives a redshift in maximum absorption coefficient in the range of 731.69-1112.86 nm in a solvent. In addition, newly designed molecules exhibited significantly narrower bandgaps (ranging from 1.33 eV to 1.93 eV) than SJ-IC having a bandgap of 2.01 eV. Similarly, newly designed molecules show significantly less excitation energy in gaseous and solvent phases than SJ-IC. Furthermore, the reorganization energies of DL1-DL7 are much lower than that of SJ-IC, indicating high charge mobility in these molecules. DL6 and DL7 have shown considerably improved open circuit voltage (VOC), reaching 1.49 eV and 1.48 eV, respectively. Thus, the modification strategy employed herein has been fruitful with productive effects, including better tuning of the energy levels, lower bandgaps, broader absorption, improved charge mobility, and increased VOC. Based on these results, it can be suggested that these newly presented molecules can be considered for practical applications in the future.