Chloro aluminum phthalocyanine-based organic thin-film transistors as cannabinoid sensors: engineering the thin film response

Abstract

Cannabis producers, retailers, and law enforcement increasingly need low-cost point-of-source cannabinoid sensors. Organic thin-film transistor (OTFT) based sensors are a promising technology that can provide rapid speciation and detection of Δ⁹-tetrahydrocannabinol (THC) while maintaining low manufacturing costs and ease of use. Herein, chloro aluminum phthalocyanine (Cl-AlPc) OTFTs were optimized through engineering film thickness (30, 50 or 100 nm) and the device source-drain geometry (W/L = 100, 200, 400, 800 and 1000), as these parameters have been shown to strongly influence OTFT performance. Optimized Cl-AlPc OTFT based sensors were exposed to both THC solution and THC vapor, demonstrating that improved device performance was not directly correlated with increased sensitivity. Grazing-incidence wide-angle X-ray scattering (GIWAXS) and atomic force microscopy (AFM) were used to interrogate thin-film morphology. While little change in molecular orientation resulted from film thickness or exposure to THC, the data suggests that the improved sensing response of Cl-AlPc-derived devices is directly related to increased thin-film surface area resulting from increased roughness and reduced film thickness.