Molecular design of D-π-D-typed hole-transporting materials for perovskite solar cells based on the π-conjugated cores

The performances of four new D-pi-D-typed hole-transporting materials (HTMs) with big n-conjugated linkers are simulated with density functional theory and the Marcus hopping model. Our results show that the highest occupied molecular orbital (HOMO) levels of new designed HTMs range from - 5.22 to -5.39 eV, which presents a suitable energy alignment with the valence band of perovskite. Meanwhile, due to the strong electronic coupling between adjacent molecules and delocalized frontier molecular orbitals, the high hole mobilities are also obtained for these molecules with values of 1.03 x 10(-1) cm(2) v(-1) s(-1) (L1), 3.67 x 10(-2) cm(2) v(-1) s(-1) (L2), 1.05 x 10(-2) cm(2) v(-1) s(-1) (L3), and 3.66 x 10(-1) cm(2) v(-1) s(-1) (L4), respectively. Moreover, the weak absorption in visible light region and the large Stokes shifts will be also helpful to improve the performance of HTMs. In summary, the calculated results indicate that these new designed molecules with polycyclic n-conjugated cores could become potential HTM candidates to help create more efficient solar cells.