Effect of it-linker extension on property of fluorene-based hole-transporting materials for perovskite solar cells

As it-linkers, conjugated bithiophene and trithiophene are respectively introduced into hole-transporting materials (HTMs) V86-2T and V86-3T to substitute thiophene core of V862. The influence of extended it-linkers on the electronic properties and spectral properties were investigated by employing the density functional theory (DFT). The results indicate that the obvious red-shifted, wide UV-Vis absorption range and high absorption strength are achieved. To further understand the effect of increasing thiophene rings of it-linker in HTMs on the hole transport properties in perovskite solar cells (PSCs), the hole mobility of HTMs was evaluated quantitatively by Marcus theory and Einstein relation. The calculated hole mobility of V86-2T is the largest relative to V862 and V86-3T due to the more efficient intermolecular it-it stacking. The V86-2T is likely to be a promising high performance HTMs because of its excellent hole mobility, solubility and hydrophobic property, which may significantly improve the photovoltaic performance of PSCs.