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 center dot center dot center dot S) intramolecular interactions and resulting SF-DTBT and DFDTBT 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 center dot center dot center dot 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).