Graphene-Enhanced Screen-Printed BiFeO3‑Based Thermistors

In this study, serigraphic-grade BiFeO3-based ink formulations are produced and then mixed with graphene to enhance the performances of screen-printed thermistor devices. The devices are printed atop a standard thermally boosted glass-reinforced epoxy (FR-4) substrate coated with interdigitated gold electrodes. The broader operating temperature range of these thermistors makes them compatible with standard printed circuit board (PCB) manufacturing and operating conditions. Thus, we achieve highly sensitive devices with a temperature coefficient of resistance (TCR) of −0.96%/°C, which is the highest sensitivity reported yet for any graphene-based thermistor operating from 25 to 170 °C. The best-performing devices are loaded with 3.5 wt % graphene. These low-hysteresis and stable thermistors boast a thermal index (β-coefficient) of 864 K. This optimal graphene loading occurs just above the percolation threshold.