Di(9-methyl-3-carbazolyl)-(4-anisyl)amine is presented
as an effective
hole-transporting material suitable for application in perovskite
solar cells. It is obtained by a three-step synthesis from inexpensive
starting compounds. It has a relatively high glass transition temperature
of 93 °C and thermal stability with 5% weight loss at 374 °C.
The compound exhibits reversible double-wave electrochemical oxidation
below +1.5 V and polymerization at higher potential. A mechanism for
its oxidation is proposed based on electrochemical impedance and electron
spin resonance spectroscopy investigations, ultraviolet–visible–near-infrared
absorption spectroelectrochemistry results, and density functional
theory-based calculations. Vacuum-deposited films of the compound
are characterized by a low ionization potential of 5.02 ± 0.06
eV and hole mobility of 10–3cm2/(Vs)
at an electric field of 4 × 105V/cm. The newly synthesized
compound has been used to fabricate dopant-free hole-transporting
layers in perovskite solar cells. A power conversion efficiency of
15.5% was achieved in a preliminary study.