Air-Stable Spin-Coated Naphthalocyanine Transistors for Enhanced Chemical Vapor Detection

Abstract

Air-stable organic thin-film transistor (OTFT) sensors fabricated using spin-cast films of 5,9,14,18,23,27,32,36-octabutoxy-2,3-naphthalocyanine (OBNc) demonstrated improved chemical vapor sensitivity and selectivity relative to vacuum-deposited phthalocyanine (H(2)Pc) OTFTs. UV-vis spectroscopy data show that annealed spin-cast OBNc films exhibit a red-shift in the OBNc Q-band λ(max) which is generally diagnostic of improved π-orbital overlap in phthalocyanine ring systems. Annealed OBNc OTFTs have mobilities of 0.06 cm(2) V(-1) s(-1), low threshold voltages (|V(th)| < 1 V), and on/off ratios greater than 10(6). These air-stable device parameters are utilized for sensing modalities which enhance the sensitivity and selectivity of OBNc OTFTs relative to H(2)Pc OTFTs. While both sensors exhibit mobility decreases for all analytes, only OBNc OTFTs exhibit V(th) changes for highly polar/nonpolar analytes. The observed mobility decreases for both sensors are consistent with electron donation trends via hydrogen bonding by basic analytes. In contrast, V(th) changes for OBNc sensors appear to correlate with the analyte's octanol-water partition coefficient, consistent with polar molecules stabilizing charge in the organic semiconductor film. The analyte induced V(th) changes for OBNc OTFTs can be employed to develop selective multiparameter sensors which can sense analyte stabilized fixed charge in the film.

Tuning Coating Thickness of Iron Tetraphenyl Porphyrin on Single Walled Carbon Nanotubes by Annealing: Effect on Benzene Sensing Performance

“…This allowed to infer that possibly, irregular coating at 150 °C resulted in decreased level of electron donation to the SWCNTs backbone and certainly, conduction was dominated by electrical behavior of pristine SWCNTs. Finally, an intermediate conduction behavior (with device current ≈2.492 times than that of S 1 ) for S 2 could be attributed to optimum coating thickness resulted at 90 °C and annealing induced long range ordering of the FeTPP layer. An optimum thickness of functionality layer regulates favorable level of electron donation while enhanced π–π overlap between adjacent porphyrin rings and π delocalization at SWCNTs/FeTPP interface is offered by long range ordering.…”

Naphthalocyanine Thin Films and Field Effect Transistors

“…This data in SI also includes measurements of devices grown at room temperature for which the mobility in vacuum (air) is ~ 10 -5 cm 2 /Vs (~ 10 -4 cm 2 /Vs), several orders of magnitude lower than the maximum value. It is known that an increase in current flowing FETs formed from solubilised Nc derivatives can occur in the presence of oxidising species through their action as electron acceptors 9 . Our observation of a shift of threshold voltage to less negative values is consistent with an increase in hole concentration which compensates traps, either in the dielectric layer or at the interfaces of the Nc film.…”

“…Dye molecules derivatised from phthalocyanine (Pc) and the larger analogue molecule, naphthalocyanine (Nc) have attracted much attention as candidate materials for photovoltaic devices, field effect transistors, gas sensing and organic spintronic devices [1][2][3][4][5][6][7][8][9][10][11][12][13] .…”

Cobalt phthalocyanine-based submicrometric field-effect transistors

“…Metal phthalocyanines (MPc) have high chemical and thermal stability as well as interesting semiconducting properties, which make them excellent candidates for organic field effect transistors (OFETs) . In addition, the strong charge transport dependence on the chemical environment makes them also good candidates for chemical sensing.…”