DFT and TD-DFT calculations of the electronic structures and photophysical properties of newly designed pyrene-core arylamine derivatives as hole-transporting materials for perovskite solar cells

The electronic structures and photophysical properties of three newly designed pyrene (PY) core arylamine derivatives as hole-transporting materials (HTMs) have been studied by DFT and TD-DFT methods. The modifications made in the arylamine wings of the well-studied and successful HTM PYC compound result in three HTMs designated as HTM1, HTM2, and HTM3. Four of the (methoxyphenyl)amine rings in PYC were replaced by (methoxyphenyl) thiophene (HTM1), (methoxyphenyl) furan (HTM2) and (methoxyphenyl) pyrrole (HTM3). The calculated HOMO and LUMO levels of HTMs 1-3 show proper energy matching and hole-injecting layer, indicating that the hole transports of the HTMs 1-3 compounds are very comparable with that of PYC. The matching of HOMO levels of HTM1 and HTM2 and the LUMO level of HTM3 is even better than that of PYC compound. The FMO analysis elucidated that the PY core acts as an electron withdrawal and contributes mainly to LUMO levels and the arylamine wings act as an electron-donating group and contribute mainly to HOMO levels. HTMs 1-3 show large Stokes shifts based on their absorption and emission spectra. Additionally, the hole reorganization energy is less than that of electrons. Thus, their hole mobility is better than their electron mobility. Furthermore, the ionization potentials, electron affinities, and hardness values were also calculated and compared to evaluate the performance of the newly designed HTMs. The nonlinear optical properties for the newly designed HTMs 1-3 have been investigated as they are correlated with the photoelectric conversion performance. We have also predicted the hole and electron mobility of molecules, and the calculated hole mobility values are better than the electron mobility, so it can be concluded that these materials would be competent hole transfer materials.