Gate voltage effect on fluorinated and non-fluorinated copper phthalocyanine OTFT-based ammonia sensors

Abstract

Organic thin-film transistors (OTFTs) have emerged as a promising platform for gas sensing applications due to their low-power operation, room-temperature sensitivity, and structural tunability. In this work, we investigate the effect of gate voltage (VGS) on the ammonia (NH₃) sensing performance of OTFT-based sensors using copper phthalocyanine (CuPc, p-type) and fluorinated copper phthalocyanine (F16CuPc, n-type) as the active layers for the first time. Devices were exposed to NH₃ concentrations ranging from 0 to 100 ppm, and their electrical responses were monitored across different VGS values. Results demonstrate that modulating VGS significantly impacts key sensing parameters, including relative response (RR), sensitivity, limit of detection (LOD), and response/recovery kinetics. The lowest LODs achieved were 0.4 ppm for CuPc and 0.21 ppm for F16CuPc. These findings highlight the potential of VGS modulation as a powerful strategy to optimize OTFT sensor performance and provide a new dimension of tunability for gas detection technologies at room temperature.