Monitoring of the energy levels by heteroatom substitution to hexacene and controlling over singlet fission and photo-oxidative resistance

[Display omitted] •For effective singlet fission to increase solar cell efficiency, a series of new silicon substituted hexacene derivatives are designed.•The efficiency of those materials is investigated using the SF thermodynamic criteria.•We have shown the SF energy criteria satisfied by the singlet and triplet states of various silahexacene isomers, and theoretically predicted whether such molecules exhibit fission properties or not.•The F is substituted in those silahexacenes for lowering frontier molecular orbital energies effectively.•The geometries, electronic structures, frontier molecular orbital energies, excited state energies associated with singlet fission process of those substituted hexacene are investigated with well known ORCA quantum mechanical method. The singlet fission is a spin allowed and extremely fast internal conversion process involved in solar cell by which a photo-excited singlet exciton is splitted into two triplet ones. For effective singlet fission and to increase the efficiency of solar cell, designing of new molecules is an interesting area of research and our current interest. The silicon substituted oligocenes, commonly known as silaoligocenes, are found to be the efficient singlet fission material due to their special characteristics. We have shown the SF energy criteria satisfied by the singlet and triplet states of various silahexacene derivatives, and theoretically predicted whether such molecules exhibit fission properties or not. The fluorine atoms have been substituted to various positions of different silahexacenes to manipulate their singlet and triplet energy levels. As fluorine being the most electro-negative substituent, it is capable of lowering frontier molecular orbital energies effectively. Thus, the material can easily match SF energy criteria to compute the SF driving force or triplet–triplet annihilation possibility. The geometries, electronic structures, frontier molecular orbital energies, optimization of excited state and calculation of energies associated with fission process of the substituted hexacene are investigated with well known quantum mechanical methods.