The strategy for high-efficiency hole conductors by engineering short-range intramolecular interactions

The strategy of introducing short-range intramolecular interactions was adopted to small organic molecular hole-transporting materials (HTMs) for perovskite solar cells (PSCs), which effectively modulates the molecular configuration for achieving higher carrier mobility and higher molecular planarity than the control. Upon incorporation of short-range fluorine-sulfur (F⋯S) intramolecular interactions and resulting SF-DTBT and DF-DTBT in comparison with DTBT based contrast, we realize a significant enhancement of molecular planarity, where the dihedral angle of the DF-DTBT is decreased to one-tenth with the introduction of short-range F⋯S intramolecular interactions compared with the DTBT. In addition, the fluorine atoms in molecule also enhance the electron-withdrawing ability of HTMs, which benefits deepening the HOMO energy level of HTMs and realizing higher V oc for PSCs. The hole mobility of DF-DTBT and SF-DTBT are increased by 159% and 71% compared to that of DTBT. Thus, the dopant-free DF-DTBT based PSCs achieve a high efficiency of 18.7% with a high V oc (1.1 V). This work demonstrates the great potential of engineering short-range intramolecular interaction in designing efficient hole transporting materials (HTMs) for perovskite solar cells (PSCs). • Short-range intramolecular interactions were introduced for planar small organic molecular HTMs. • Fluorine-sulfur in molecule decrease the dihedral angle from 11° to 1°. • The PSCs based on un-doped DF-DTBT achieve a PCE of 18.7%.