Two‐Step Solution‐Processed Two‐Component Bilayer Phthalocyaninato Copper‐Based Heterojunctions with Interesting Ambipolar Organic Transiting and Ethanol‐Sensing Properties

Abstract

International audienceThe two-component phthalocyaninato copper-based heterojunctions fabricated from n-type CuPc(COOC8H17)(8) and p-type CuPc(OC8H17)(8) by a facile two-step solution-processing quasi-Langmuir-Shafer method with both n/p- and p/n-bilayer structures are revealed to exhibit typical ambipolar air-stable organic thin-film transistor (OTFT) performance. The p/n-bilayer devices constructed by depositing CuPc(COOC8H17)(8) film on CuPc(OC8H17)(8) sub-layer show superior OTFT performance with hole and electron mobility of 0.11 and 0.02 cm(2) V-1 s(-1), respectively, over the ones with n/p-bilayer heterojunction structure with the hole and electron mobility of 0.03 and 0.016 cm(2) V-1 s(-1) due mainly to the more intense face-to-face - interaction in the CuPc(OC8H17)(8) sub-layer than that in CuPc(COOC8H17)(8) sub-layer, revealing the effect of different stacking sequence on tuning the OTFT performance of phthalocyanine-based bilayer heterojunctions. Furthermore, the chemiresistive devices fabricated from the p/n-bilayer heterojunction, with both Au and Indium tin oxide (ITO) interdigitated electrodes (IDEs), also display much better sensing properties to ethanol than those with n/p-bilayer heterojunction in terms of sensitivity and reversibility. Significantly, time-dependent current plot of the p/n-bilayer heterojunction with ITO IDEs reveals a detection limit as low as 100 ppm, nearly complete reversibility, and high selectivity to ethanol even at room temperature, rendering this novel two-component heterojunction device a great application potential in practical detecting ethanol

Hierarchical Self‐Assembly of Tetrakis(1‐pyrenyl)porphyrins into Microscopic Petals and Flowers with Ultrasensitive Room‐Temperature NO2 Sensing in a Broad Humidity Range

“…A static recovery period (full recovery time) varied respectively from 1.6 to 7 min for 1 and 1.7 to 9 min for 2 to ensure the almost complete recovery after the test gas has been released. As can be seen in Figure and , the negative current responses for the aggregates of 1 and 2 were obtained upon exposure to electron‐accepting NO 2 gases, which are consistent with the sensing behavior reported previously for n‐type semiconductors, respectively . The response to NO 2 for the aggregates of both 1 and 2 highly increased with the increased RH value, Figure (A–C) and 8(A–C).…”

“…The higher conductivity of 2 with respect to that of 1 might be attributed to the higher ordered molecular arrangement due to the stronger π‐π interactions among the adjacent molecules in the aggregate of 2 as revealed by the UV‐vis, IR spectra and SEM experiments. A similar trend in conducting performance has previously been observed for porphyrins, phthalocyanines and amphiphilic perylene diimides . This result again revealed that the effect of metal center of in‐plane cobalt(II) porphyrin on the tuning of the intermolecular stacking, which then impacts on the electrical conductivity of the materials.…”

“…[22][23] Therefore, a blue-shifted Soret-band of 2 relative to that of 1 confirmed unambiguously the formation of in-plane CoT[(Pyr) 4 ] P where Co(II) ion has been successfully embedded into the cavity of the porphyrin ligand. When H 2 T[(Pyr) 4 ]P (1) and CoT [(Pyr) 4 ]P (2) (1 × 10 À 3 mol/L) form the self-assembled aggregates in CH 2 Cl 2 /CH 3 OH mixed solvent (1/5 v/v), the spectral shapes are all significantly broadened, which could be ascribed to the field effects of the closely compacted molecular assembly, [14] Figure 1A (lines c-d). Meanwhile, both the Soret and Q bands of the aggregates all shift to longer wavelength (462, 533, 564, 602, 662 nm for 1, and 465, 557 nm for 2), as compared to those in solution ( Figure 1A and Table S1), respectively, indicating the formation of J-aggregation-type (edge-to-edge) molecular packing structure in the aggregates of both 1 and 2, on the basis of exciton theory and previously published result.…”

“…[5][6][7][8] Among the large family of organic semiconductor materials, tetrapyrrole derivatives including porphyrins and phthalocyanines with large π-conjugated electronic molecular structures have attracted considerable research interest owing to their high thermal and chemical stability and rich substitution chemistry as well as strong π-π intermolecular interaction in solid state, resulting in intriguing electronic and optical properties [9] and potential applications as gas sensor. [4,[10][11][12][13][14] For example, a vacuum deposited film of cobalt phthalocyanine is revealed to exhibit a quite stable response and discrimination between 12, 25 and 50 ppm of NH 3 over the 10-70% RH range. [4] However, articles which focus specifically on cross sensitivity between NO 2 and humidity are quite rare.…”

Controlled Carbon Doping in Anatase TiO2 (101) Facets: Superior Trace‐Level Ethanol Gas Sensor Performance and Adsorption Kinetics

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years, many efforts have been made toward tuning structural and electronic properties of metal oxides to reduce the working temperature and enhancing gas sensor performance. [17][18][19][20] But most of these cases, metal oxide sensors have to be operated at high temperature or under UV irradiation conditions because of their large bandgap. MOS gas sensors based chemiresistive sensors have ability to measure and monitor trace level concentration of hazardous gases such as NO x , CO x , NH 3 , CH 4 , H 2 S, and SO 2 .

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