UV–Ozone Interfacial Modification in Organic Transistors for High-Sensitivity NO2 Detection

A new type of nitrogen dioxide (NO₂) gas sensor based on copper phthalocyanine (CuPc) thin film transistors (TFTs) with a simple, low-cost UV–ozone (UVO)-treated polymeric gate dielectric is reported here. The NO₂ sensitivity of these TFTs with the dielectric surface UVO treatment is ≈400× greater for [NO₂] = 30 ppm than for those without UVO treatment. Importantly, the sensitivity is ≈50× greater for [NO₂] = 1 ppm with the UVO-treated TFTs, and a limit of detection of ≈400 ppb is achieved with this sensing platform. The morphology, microstructure, and chemical composition of the gate dielectric and CuPc films are analyzed by atomic force microscopy, grazing incident X-ray diffraction, X-ray photoelectron spectroscopy, and Fourier transform infrared spectroscopy, revealing that the enhanced sensing performance originates from UVO-derived hydroxylated species on the dielectric surface and not from chemical reactions between NO₂ and the dielectric/semiconductor components. This work demonstrates that dielectric/semiconductor interface engineering is essential for readily manufacturable high-performance TFT-based gas sensors.

Highly sensitive nitrogen dioxide gas sensors based on organic thin-film transistors (OTFTs) having a low-cost UV–ozone-treated polymeric gate dielectric are fabricated. The enhanced sensing performance originates from UV–ozone-induced hydroxylated species on the dielectric surface. This work demonstrates that simple dielectric–semiconductor interface engineering can be utilized to realize OTFT-based gas sensors with excellent sensitivity and selectivity.

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