A custom-designed
ferrocene-functionalized fulleropyrrolidine derivative
Fullerene-Fc has been synthesized, which proves to be a feasible material
to improve the performance of solid-state electrochromic devices.
The molecule can be used as a dopant to design devices on substrates
of rigid (glass) as well as flexible (PET) nature. The switching speed
of devices made using poly(3-hexylthiophene) and ethyl viologen could
be improved to display a switching time of less than 1 s when the
Fullerene-Fc molecule was added. The improvement in the performance
of the electrochromic device is likely due to the solution processability
of the Fullerene-Fc molecule compatible with other used electrochromic
active materials, which helps to facilitate the necessary charge carriers
for the redox reaction within the device. Additionally, a coloration
efficiency of more than 350 cm2/C and cyclic stability
of up to 500 s were shown by the device with a color contrast of more
than 40%. Furthermore, the Fullerene-Fc molecule in the P3HT/EV device
can be incorporated to fabricate an all-organic flexible device. The
charge storage properties of fullerene and the redox behavior of ferrocene
make it a good choice to be used as an electrochromic performance
enhancer.