Theoretical design and DFT calculations were done to find new SF chromophores to be used in high efficiency organic solar cells. These included 6 new compounds which had boron, nitrogen, selenium, TIPS, and phenyl groups. All of these molecules demonstrated near planar geometries with extended pi-conjugation and had HOMO-LUMO gaps between 3.04 and 3.32 eV. The excitation energies for the singlet and triplet states were in the 2.11-2.25 eV and 1.00-1.10 eV, leading to singlet triplet energy gaps which ranged from 1.11-1.16 eV. All compounds met the critical energetic requirement for efficient singlet fission whereby ES1 >2ET1 for all chromophores. Some selected derivatives like N1 and N4 were found to have ?EST values of 1.15 eV and 1.14 eV respectively which are equal or greater than the benchmark value of pentacene which is 1.02 eV and diketopyrrolopyrrole which is 1.18 eV. Moreover, the new chromophores are expected to have greater absorption and thermal stability spectrum making them better suited for next generation organic solar cells. This study highlights the promise of heteroatom and functional group rational design for SF-active materials with advanced optoelectronic and device-engineering properties.
Riyadh R. Al-Araji (Thu,) studied this question.