N-channel Semiconductor Research Articles

Thienyl naphthodipyrrolopyrrole (TNDP)-based polymers semiconductor for n-type OFETs

Naphthodipyrrolopyrrole (NDP)-based materials as the n-type semiconductor materials are investigated, which present a good electron transport mobility. However, all the reported NDP were phenyl-substituted ones (PhNDP). Compared to the phenyl substituted chromophore, the thiophene substituted ones were often more promising due to its small size, S⋯S interaction, as well as the electron-rich behavior for the thiophene. Thus, in this work the new chromophore thiophene-substituted NDP (TNDP) was designed and synthesized for the first time via Knoevenagel reaction. In addition, two donor-acceptor typed copolymers PNDP-2T and PNDP-IDT containing TNDP were prepared. The result showed that the two polymers present not only a good aggregation and strong intramolecular charge transfer (ICT) effect, but also a low lowest unoccupied molecular orbital (LUMO) ∼ -4.17 eV. This is advantageous for the charge transport within the single molecules as well as across the neighboring polymer chains. In addition, the low LUMO energy level is beneficial for the electron injection from electrode into the semiconductor layer. As a consequence, both polymers presented n-type behavior. The electron transport mobility of PNDP-IDT was up to 0.99 cm2 V−1 s−1, which is among the highest electron mobility reported for conjugated polymers. In addition, this value is higher than the PNDP-based polymers with similar chemical structure. This work clearly shows that TNDP is an appealing electron-deficient building block for novel π-conjugated polymers with application potential in the n-channel semiconductors.

Naphthalene imide derived BODIPY analogues as n-channel semiconductors

BODIPY analogues based on naphthalene mono-imides have been synthesized. The single-crystal X-ray diffraction studies provided evidences for their molecular structures, conformational features and stacking states. The effects of the boron difluoride chelation on the optical and redox properties of the dyes were investigated. The presence of difluoroboranyls in the naphthalene imides led to modifications in the electronic structure of the molecules. The LUMO energy level of the BF2-containing dye (NIPBF) was reduced by 0.15 eV in comparsion with naphthalene-diimides. The field-effect transistors devices based on the BODIPY analogues exhibited typical n-type behavior with electron mobility up to 0.10 cm2 V−1 s−1.

Perhalogenated Tetraazaperopyrenes and Their Corresponding Mono- and Dianions.

Chlorination and bromination of 2,9-perfluoropropyl-substituted tetraazaperopyrenes (TAPPs) under forcing conditions resulted in fully core-halogenated TAPP derivatives, devoid of hydrogen atoms at the polycyclic aromatic core. The octahalogenation stabilized the reduced mono- and dianionic compounds sufficiently to allow for their characterization. The additional ortho-chlorination led to an improvement of the electron mobility compared to the bay-substituted tetrachloro-TAPP when employed as an n-channel semiconductor in thin-film transistors.

5,7,12,14-Tetrafunctionalized 6,13-Diazapentacenes.

The synthesis, property evaluation, and single crystal X‐ray structures of four 5,7,12,14‐tetrafunctionalized diazapentacenes are presented. The synthesis of these compounds either starts from tetrabromo‐N,N‐dihydrodiazapentacene or from a diazapentacene tetraketone. Pd‐catalyzed coupling or addition of a lithium acetylide gave the precursors that furnish, after further redox reactions, the diazapentacenes as stable crystalline materials. The performance of the tetraphenyl‐substituted compound as n‐channel semiconductor was evaluated in organic field effect transistors.

A Solution-Processable meso-Phenyl-BODIPY-Based n-Channel Semiconductor with Enhanced Fluorescence Emission.

The molecular design, synthesis, and characterization of an acceptor-donor-acceptor (A-D-A) semiconductor BDY-Ph-2T-Ph-BDY comprising a central phenyl-bithiophene-phenyl π-donor and BODIPY π-acceptor end-units is reported. The semiconductor shows an optical band gap of 2.32 eV with a highly stabilized HOMO/LUMO (-5.74 eV/-3.42 eV). Single-crystal X-ray diffraction (XRD) reveals D-A dihedral angle of ca. 66° and strong intermolecular "C-H ⋅⋅⋅ π (3.31 Å)" interactions. Reduced π-donor strength, increased D-A dihedral angle, and restricted intramolecular D-A rotations allows for both good fluorescence efficiency (ΦF =0.30) and n-channel OFET transport (μe =0.005 cm2 /V ⋅ s; Ion /Ioff =104 -105 ). This indicates a much improved (6-fold) fluorescence quantum yield compared to the meso-thienyl BODIPY semiconductor BDY-4T-BDY. Photophysical studies reveal important transitions between locally excited (LE) and twisted intramolecular charge-transfer (TICT) states in solution and the solid state, which could be controlled by solvent polarity and nano-aggregation. This is the first report of such high emissive characteristics for a BODIPY-based n-channel semiconductor.

N-Heteroacenes and N-Heteroarenes as N-Nanocarbon Segments.

N-Heteroacenes and N-heteroarenes are the heterocyclic congeners of the acenes and arenes, in which one or several perimeter C-H bonds have been substituted by pyridine-type nitrogen atoms. They are formally segments out of N-doped nanographenes. Position and number of the nitrogens vary greatly, making N-heteroacenes and N-heteroarenes define a vast class of N-nanographene segments; they display modular electronic and structural properties. The nitrogen atoms in the perimeter lead to finely tunable frontier molecular orbital positions and therefore improved electron affinity and higher oxidative stability but conversely also require and allow different synthetic approaches than those reported for the synthesis of their hydrocarbon and nanographene analogues. The chemistry of N-heteroarenes, despite being known for more than a century, has made significant progress in the last years and established these materials both as powerful n-channel semiconductors in thin film transistors and as useful emitters in organic light emitting diodes (OLEDs) and in photovoltaic devices. The electronegative nitrogen atoms impart a deep LUMO into the azaacenes and azaarenes, improve electron injection, and enable powerful electron transport but also charge separation in bulk-heterojunction type organic photovoltaic (OPV) devices. At the same time, azaacenes and azaarenes are fundamentally exciting materials that push the limits of structure and stability, constantly displaying novel topologies and structures as variations of a simple leitmotif; we expect a bright future for esthetically pleasing yet highly functional N-heterocyclic species. Firstly, we discuss novel structures and structural elements that have evolved during the lastyears in N-heteroacene and N-heteroarene chemistry and delineate their properties. An important aspect is the oligomerization or better multimerization of azaacene and azaarene units into novel and surprising topologies, in which multiple azaarenes or azaacenes are stitched together. Examples are tetrahedral assemblies of tetraazapentacenes but also cyclic tetramers of different types of azaacenes and linearly bent, S-shaped, formally dimeric species. An exciting aspect of the exploration of the structural manifold of azaacenes is their electronic interaction in such assemblies and their solid-state microstructure. A further aspect of this work is the increase in size of the azaacenes and concepts that allow stabilization of the larger congeners. The attachment of four benzo units to the azaacene core is a powerful concept that stabilizes tetraazaheptacenes and should also be useful to achieve persistent tetraazanonacenes. Secondly, we describe the success of N-heteroacenes and N-heteroarenes in organic electronic devices; specifically, the use of symmetrical halogenated tetraazapentacenes as superb n-channel transistor materials with air stable and persistent radical anions as charge carriers; we discuss the structural reason for their success. Use of azaacenes and azaarenes is not restricted to transistors, but they are also applied in bulk heterojunction photovoltaic devices and in brightly emitting OLEDs. Azaacenes and azaarenes are attractive segments out of hetero-nanographenes and objects of study, starting from fundamental structural and topological questions, ranging to powerful applications in organic electronics. The general interest in azaacenes is witnessed by the constantly increasing number of groups who discover and work on these materials as novel functional and flexible species.

Ambipolar thin-film transistors based on organic semiconductor blend

Abstract Ambipolar thin-film transistors are fabricated employing p-channel (2-decyl-7-phenylbenzo[b]benzo [4,5]thieno[2,3-d]thiophene; Ph-BTBT-C10) and n-channel (N,N'-di-n-octyl-3,4,9,10-perylenetetracarboxylic diimide; PTCDI-C8) semiconductors in bilayer and bulk heterojunction architecture. Bilayer organic semiconductors with small thickness of the first layer exhibit ambipolar device characteristics with relatively poor electrical performance. On the other hand, bulk heterojunction organic thin-film transistors (OTFTs) with optimized blend ratio exhibited higher ambipolar charge transport properties with carrier mobility as high as 0.22 and 0.038 cm2 V−1s−1 for hole and electron, respectively. Complementary-like inverters fabricated based on optimized bulk heterojunction OTFTs show high transfer gain of 96.

Thioether- and sulfone-functionalized dibenzopentalenes as n-channel semiconductors for organic field-effect transistors

Dibenzo[a,e]pentalenes, functionalized with thioether or sulfone groups, show high electron mobilities in n-channel OFETs using well-aligned crystals.

Solution-processable dithieno[3,2-b:2′,3′-d]thiophene derivatives for organic thin-film transistors and complementary-like inverters

Abstract Solution-processable dithieno[3,2-b:2′,3′-d]thiophene (DTT) derivatives, 2,6-bis(phenylethynyl)dithieno[3,2-b:2′,3′-d]thiophene (BP-Et-DTT) and 2,6-bis(thiophen-2-ylethynyl)dithieno[3,2-b:2′,3′-d]thiophene (BT-Et-DTT) were synthesized and characterized as organic semiconductors for organic thin-film transistors (OTFTs). Thermal, optical, and electrochemical properties of the DTT-based semiconductors were investigated. The solution-sheared thin films based on DTT derivatives exhibited p-channel characteristics as an active layer in organic thin-film transistors. The highest hole mobility was 0.32 cm2 V−1s−1 based on BP-Et-DTT thin films. The thin films exhibited micrometer-sized crystalline fiber structures which were aligned along the shearing direction, resulting in fiber-alignment-induced charge-transport anisotropy. Furthermore, bulk heterojunction (BHJ) ambipolar transistors were fabricated with an optimized blending ratio of BP-Et-DTT and the representative n-channel semiconductor, PDIFCN2. Complementary-like inverters were fabricated based on the two identical ambipolar transistors, resulting in moderate voltage gains of up to 16.

Novel n-channel organic semiconductor based on pyrene-phenazine fused monoimide and bisimides

Large π-conjugated pyrene-phenazine monoimide and bisimides were synthesized by imine condensation reaction. These imides form well ordered 1D nanotapes upon self-assembly in solution. Electrochemical and electric conductivity measurement reveal it can be served as an n-channel semiconductor with large charge carrier mobility up to 4.1cm2V−1s−1. Both alkylated imides are highly luminescent, and can be quenched via protonization using trifluoroacetic acid, which could be served as potential colorimetric acid sensors.

Room temperature ethanol sensing properties of FET sensors based on ZnO nanostructures

Abstract In this work, the ethanol sensing properties of field effect transistor (FET) sensors based on ZnO nanostructures were investigated at the room temperature and compared with those of based on ZnO thin film. ZnO thin film was deposited by RF magnetron sputtering. While ZnO nanostructures were prepared by a thermal oxidation technique. They were completely configured as the bottom gate FET structures. It was found that our devices exhibit the n-channel semiconductor with a drain-source current on/off ratio in order of 105 and 104 for ZnO thin film and ZnO nanostructures, respectively. In addition, the sub-threshold swing (SS) of ZnO nanostructures extremely change with ethanol supply flowed into the system. It can be seen that this SS of FET with ZnO nanostructures in air is found to be 1.5 V/decade. On the other hand, the SS of devices are achieved with the value of 1.1 and 0.7 V/decade for the ethanol concentrations of 50 and 100 ppm, respectively. The sensor response of FET sensor based on ZnO nanostructures is about 6 whereas thin film structure is about 3 at 100 ppm concentration. This suggests the sensor response improvement of FET sensors at the room temperature due to surface to volume ratio effect of nanostructures formation.

Benzothiadiazole-Based Small-Molecule Semiconductors for Organic Thin-Film Transistors and Complementary-like Inverters.

New benzothiadiazole derivatives, 4,7-bis(5-phenylthiophen-2-yl)benzo[c][1,2,5]thiadiazole (PT-BTD) and 4,7-bis[4-(thiophen-2-yl)phenyl]benzo[c][1,2,5]thiadiazole (TP-BTD), were synthesized and characterized as small-molecule organic semiconductors for organic thin-film transistors (OTFTs) and complementary inverters. The thermal, optical, and electrochemical properties of the new compounds were fully characterized. Vacuum-deposition and solution-shearing methods were used to fabricate thin films based on these compounds. Thin films based on PT-BTD exhibited p-channel characteristics with hole mobilities as high as 0.10 cm2 V-1 s-1 and current on/off ratios >107 for top-contact/bottom-gate OTFT devices. With an optimized blending ratio of PT-BTD and the representative n-channel semiconductor N,N'-1H,1H-perfluorobutyl dicyanoperylenediimide, bulk heterojunction ambipolar transistors were fabricated with balanced hole and electron mobilities of 0.10 and 0.07 cm2 V-1 s-1 , respectively. Furthermore, a complementary-like inverter was fabricated using ambipolar thin-film transistors, which showed a high voltage gain of 84.

Parylene based bilayer flexible gate dielectric layer for top-gated organic field-effect transistors

In this paper, we report on a bilayer insulating film based on parylene-c for gate dielectric layers in top-gate/bottom-contact inkjet-printed organic field-effect transistors (OFETs) with indacenodithiophene-co-benzothiadiazole (IDTBT) and poly([N,N’-bis(2-octyldodecyl)-naphthalene-1,4,5,8-bis(dicarboximide)-2,6-diyl]-alt-5,5’-(2,2’-bitthiophene)) (P(NDI2OD-T2)) as with p- and n-channel semiconductors. The thin parylene-c film (t = 210 nm) show large gate leakage density (2.52 nA/cm2 at 25 V) and low breakdown voltage (2.2 MV/cm). In addition, a degraded field-effect mobility (μ) was observed in printed IDTBT and P(NDI2OD-T2) OFETs with the parylene-c single-layered dielectric. X-ray photoelectron spectroscopy (XPS) analysis reveals that the degradation of μ is due to unwanted chemical interaction between parylene-c and the conjugated polymer surface during the parylene-c deposition process. By inserting 50-nm thick poly(methyl-methacrylate) (PMMA) and polystyrene (PS) layer in-between the parylene-c and conjugated polymer film, highly improved gate leakage density and breakdown voltage are achieved. The printed IDTBT and P(NDI2OD-T2) OFETs with a bilayer dielectric compose of parylene-c and PMMA and PS show significantly improved hole and electron μ of 0.47 cm2/Vs and 0.13 cm2/Vs, respectively, and better operation stability. In addition, we demonstrate inkjet-printed polymer complementary inverter with a high voltage gain of 25.7 by applying a PS/parylene-c bilayer dielectric.

Effects of p-(Trifluoromethoxy)benzyl and p-(Trifluoromethoxy)phenyl Molecular Architecture on the Performance of Naphthalene Tetracarboxylic Diimide-Based Air-Stable n-Type Semiconductors.

N,N'-Bis(4-trifluoromethoxyphenyl) naphthalene-1,4,5,8-tetracarboxylic acid diimide (NDI-POCF3) and N,N'-bis(4-trifluoromethoxybenzyl) naphthalene-1,4,5,8-tetracarboxylic acid diimide (NDI-BOCF3) have similar optical and electrochemical properties with a deep LUMO level of approximately 4.2 eV, but exhibit significant differences in electron mobility and molecular packing. NDI-POCF3 exhibits nondetectable charge mobility. Interestingly, NDI-BOCF3 shows air-stable electron transfer performance with enhanced mobility by increasing the deposition temperature onto the octadecyltrichlorosilane (OTS)-modified SiO2/Si substrates and achieves electron mobility as high as 0.7 cm(2) V(-1) s(-1) in air. The different mobilities of those two materials can be explained by several factors including thin-film morphology and crystallinity. In contrast to the poor thin-film morphology and crystallinity of NDI-POCF3, NDI-BOCF3 exhibits larger grain sizes and improved crystallinities due to the higher deposition temperature. In addition, the theoretical calculated transfer integrals of the intermolecular lowest unoccupied molecular orbital (LUMO) of the two materials further show that a large intermolecular orbital overlap of NDI-BOCF3 can transfer electron more efficiently than NDI-POCF3 in thin-film transistors. On the basis of fact that the theoretical calculations are consistent with the experimental results, it can be concluded that the p-(trifluoromethoxy) benzyl (BOCF3) molecular architecture on the former position of the naphthalene tetracarboxylic diimides (NDI) core provides a more effective way to enhance the intermolecular electron transfer property than the p-(trifluoromethoxy) phenyl (POCF3) group for the future design of NDI-related air-stable n-channel semiconductor.

Substrate-Directed Growth of N-Heteropolycyclic Molecules on a Metal Surface

N-Heteropolycyclic compounds are promising organic n-channel semiconductors for applications in field effect transistors. The adsorption behavior of these molecules on inorganic substrates is of great interest, since it affects the transport properties. Utilizing high-resolution electron energy-loss spectroscopy (HREELS) and density functional theory (DFT), we determined the adsorption geometry of three different N-heteropolycyclic molecules as a function of coverage on Au(111). All three π-conjugated aromatic molecules adopt a planar geometry with respect to the substrate in both the monolayer (ML) and thin films (up to 10 ML). Contrary, in their crystal structure the molecules are tilted up to 82° between the molecular planes in neighboring stacks. Electronic HREELS and DFT calculations allowed the determination of the optical gaps of the molecules which are unaffected by the nitrogen substitution of the polycyclic aromatic hydrocarbons, while the frontier orbitals of the N-heteropolycyclic compounds ar...

Dipolar SAMs Reduce Charge Carrier Injection Barriers in n-Channel Organic Field Effect Transistors.

In this work we examine small conjugated molecules bearing a thiol headgroup as self assembled monolayers (SAM). Functional groups in the SAM-active molecule shift the work function of gold to n-channel semiconductor regimes and improve the wettability of the surface. We examine the effect of the presence of methylene linkers on the orientation of the molecule within the SAM. 3,4,5-Trimethoxythiophenol (TMP-SH) and 3,4,5-trimethoxybenzylthiol (TMP-CH2-SH) were first subjected to computational analysis, predicting work function shifts of -430 and -310 meV. Contact angle measurements show an increase in the wetting envelope compared to that of pristine gold. Infrared (IR) measurements show tilt angles of 22 and 63°, with the methylene-linked molecule (TMP-CH2-SH) attaining a flatter orientation. The actual work function shift as measured with photoemission spectroscopy (XPS/UPS) is even larger, -600 and -430 meV, respectively. The contact resistance between gold electrodes and poly[N,N'-bis(2-octyldodecyl)-naphthalene-1,4:5,8-bis(dicarboximide)-2,6-diyl]-alt-5,5'-(2,2'-bithiophene) (Polyera Aktive Ink, N2200) in n-type OFETs is demonstrated to decrease by 3 orders of magnitude due to the use of TMP-SH and TMP-CH2-SH. The effective mobility was enhanced by two orders of magnitude, significantly decreasing the contact resistance to match the mobilities reported for N2200 with optimized electrodes.

Voltage-Controlled Ring Oscillators Based on Inkjet Printed Carbon Nanotubes and Zinc Tin Oxide.

A voltage-controlled ring oscillator is implemented with double-gate complementary transistors where both the n- and p-channel semiconductors are deposited by inkjet printing. Top gates added to transistors in conventional ring oscillator circuits control not only threshold voltages of the constituent transistors but also the oscillation frequencies of the ring oscillators. The oscillation frequency increases or decreases linearly with applied top gate potential. The field-effect transistor materials system that yields such linear behavior has not been previously reported. In this work, we demonstrate details of a material system (gate insulator, p- and n-channel semiconductors) that results in very linear frequency changes with control gate potential. Our use of a double layer top dielectric consisting of a combination of solution processed P(VDF-TrFE) and Al2O3 deposited by atomic layer deposition leads to low operating voltages and near-optimal device characteristics from a circuit standpoint. Such functional blocks will enable the realization of printed voltage-controlled oscillator-based analog-to-digital converters.

Perfluoroalkyl-Functionalized Thiazole–Thiophene Oligomers as N-Channel Semiconductors in Organic Field-Effect and Light-Emitting Transistors

Despite their favorable electronic and structural properties, the synthetic development and incorporation of thiazole-based building blocks into n-type semiconductors has lagged behind that of other π-deficient building blocks. Since thiazole insertion into π-conjugated systems is synthetically more demanding, continuous research efforts are essential to underscore their properties in electron-transporting devices. Here, we report the design, synthesis, and characterization of a new series of thiazole–thiophene tetra- (1 and 2) and hexa-heteroaryl (3 and 4) co-oligomers, varied by core extension and regiochemistry, which are end-functionalized with electron-withdrawing perfluorohexyl substituents. These new semiconductors are found to exhibit excellent n-channel OFET transport with electron mobilities (μe) as high as 1.30 cm2/(V·s) (Ion/Ioff > 106) for films of 2 deposited at room temperature. In contrary to previous studies, we show here that 2,2′-bithiazole can be a very practical building block for high-performance n-channel semiconductors. Additionally, upon 2,2′- and 5,5′-bithiazole insertion into a sexithiophene backbone of well-known DFH-6T, significant charge transport improvements (from 0.001–0.021 cm2/(V·s) to 0.20–0.70 cm2/(V·s)) were observed for 3 and 4. Analysis of the thin-film morphological and microstructural characteristics, in combination with the physicochemical properties, explains the observed high mobilities for the present semiconductors. Finally, we demonstrate for the first time implementation of a thiazole semiconductor (2) into a trilayer light-emitting transistor (OLET) enabling green light emission. Our results show that thiazole is a promising building block for efficient electron transport in π-conjugated semiconductor thin-films, and it should be studied more in future optoelectronic applications.

Tailor-made rylene arrays for high performance n-channel semiconductors.

Rylene dyes, made up of naphthalene units linked in peri-positions, are emerging as promising key building blocks to create π-functional materials. Chemists have found uses for these ribbonlike structures in a wide range of applications of optoelectronic devices. Because their structure combines two sets of six-membered electron-withdrawing dicarboxylic imide rings, rylene diimides exhibit enhanced solubility, excellent chemical and thermal stabilities, high electron affinities, and remarkable electron-transporting properties. Among them, perylene diimide (PDI) and naphthalene diimide (NDI) derivatives are important representatives improving the performance of electron-transporting technologies, relative to their p-channel counterparts. Pioneering works by Müllen and Langhals have inspired chemists to extend the π-conjugation along the peri-positions of rylene diimides, which generally results in impressive bathochromic shifts and a nearly linear increase in the extinction coefficient. In addition, in the past years, researchers have focused on π-expansion of NDI or PDI systems through bay-functionalization with carbocyclic and heterocyclic rings annulated onto the skeleton. However, chemists have rarely investigated lateral expansion via both bay- and nonbay-functionalization to construct homologous series of rylene arrays with different electronic delocalization and fine-tuned flexible linkage. This is probably due to the lack of effective procedures for the (multi) carbon-carbon formation and annulation of electron-deficient rylene imide units. In this Account, we discuss our recent progress in the design and synthesis of laterally expanded rylene dyes based on homocoupling and cross-coupling reactions of core-functionalized PDIs and NDIs to achieve novel high performance n-channel organic semiconducting materials. These new achievements offer us opportunities to learn fundamental issues about how chemical and physical properties alter with incremental changes in structure. We highlight synthetic methodology of transition-metal mediated coupling reactions (and/or C-H transformation) for singly linked, doubly linked, and fully conjugated triply linked oligoPDIs, and further for the construction of hybrid rylene arrays via bay- and/or nonbay-functionalization. In addition, we summarize the informative correlations between the molecular structures and their optoelectronic properties, especially the modulation of progressively red-shifted absorption maxima and positive shifts in the redox potentials. This decreases the energy gaps and increases the electron-accepting abilities through expansion of π-system, which has direct impacts on the compounds' potential applications in optoelectronic devices. Finally, we introduce the promising applications of these laterally expanded rylene dyes as exceptional high performance n-channel semiconductors in organic field-effect transistors (OFETs) and competitive candidates for non-fullerene acceptors in high efficient organic photovoltaic devices (OPVs).

Printable ammonia sensor based on organic field effect transistor

We report an organic field-effect transistor (OFET)-based sensor made from printable materials with an unusually high sensitivity of 0.5ppm v/v for ammonia and with limit of detection on the order of 0.1ppm v/v. The device developed has a polyethylene terephthalate (PET) substrate, bottom contacts, and poly (3,3‴-didodecylquaterthiophene) (PQT-12) cast from 4mg/mL cholorobenzene solution as active semiconductor. The fabrication process is simplified by replacing the gate electrode and dielectric deposition steps with the introduction of static charges on the back surface of the PET substrate by corona charging, a procedure that is adaptable to roll-to-roll processing. Hydrophobic polymers applied to the back surface stabilize this charge, providing evidence for their activity at that location. In the proposed sensor, these static charges are used as a static gate, reducing the OFET architecture to a chemiresistor. The sensor is selective for ammonia over common organic solvent vapors, and the response is generally reversible. The device also demonstrates memory behavior required for dosimetric sensors when kept at low temperature (4°C to −30°C). A converse response from an n-channel semiconductor is also reported.