Tetraphenylbutadiene-Based Symmetric 3D Hole-Transporting
Materials for Perovskite Solar Cells: A Trial Trade-off between Charge
Mobility and Film Morphology
Two
three-dimensional symmetric tetraphenylbutadiene derivatives decorated
with diphenylamine or triphenylamine fragments are first prepared
for use as hole-transporting materials (HTMs) in perovskite solar
cells (PSCs). The HTMs are acquired using straightforward synthetic
methods and facile purification techniques. The thermal stability,
photophysical properties, electrochemical behaviors, computational
study, hole mobility, X-ray diffraction, hole transfer dynamics, hydrophobicity,
surface morphology, and photovoltaic performances of the HTMs are
discussed. The highest power conversion efficiency (PCE) of CJ-04-based cell is 13.75%, which is increased to 20.06% when CJ-03 is used as HTM, superior to the PCE of the cell based
on 2,2′,7,7′-tetrakis(N,N-di-p-methoxyphenylamine)-9,9′-spirobifluorene
(spiro-OMeTAD) (18.90%). The preparation cost of CJ-03 accounts for merely 23.1% of the price of commercial spiro-OMeTAD,
while the concentration of CJ-03 solution used in the
device fabrication (60.0 mg mL–1) is lower compared
with that of the spiro-OMeTAD solution (72.3 mg mL–1). These results corroborate that the screw-like HTMs with a highly
distorted configuration are facilely available and promising candidates
for PSCs. More importantly, a practical solution is proposed to achieve
moderate charge mobility and good film-formation ability of the HTMs
simultaneously.