Quantum mechanical modeling of fused rings-based small-donor molecules with enhanced optoelectronic attributes for high performance organic photovoltaic cells

Seven small molecule donors (S1-S7) have been theoretically formulated by the end-capped modeling of ac-ceptors of reference SR. Through density functional and its time-dependent theory, different photo-physical, morphological, and opto-electronic aspects of the newly reported molecules were analyzed with reference to the SR molecule. Amongst the different studied features were the absorption maxima (lambda max), transition density matrix, frontier molecular orbitals, reorganization energies of hole and electron, excitation energies, bandgaps, fill factor, and open circuit voltage (VOC), etc. Individually, the S4 molecule had the smallest bandgap and electron reorganization energy, the highest ionization potential and lambda max, as well as the smallest excitation energy in the analyzed gas and chloroform phases. While the smallest interaction coefficient was seen to be of S1. The VOC of all the donor molecules computed with respect to PC61BM acceptor revealed the greatest VOC and fill factor of S1 and S4 molecules. So, it could be understood that these molecules, with special reference to S1 and S4, might outperform SR in a variety of ways, and hence are suggested to experimentalists for future innovations of organic photovoltaic cells.

Automated summary

Seven small molecule donors (S1-S7) were theoretically formulated and their photo-physical, morphological, and opto-electronic properties were analyzed and compared to reference SR molecule. The S4 molecule exhibited the smallest bandgap and electron reorganization energy, highest ionization potential and absorption max, as well as the smallest excitation energy. The S1 molecule had the smallest interaction coefficient. The VOC and fill factor of S1 and S4 molecules were found to be the highest. Hence, these molecules, especially S1 and S4, are suggested for future innovations in organic photovoltaic cells.