Aerosol Jet Printed Carbon Nanotube-Poly(3-hexylthiophene) Bilayer Thin-Film Phototransistors with High Responsivity

Phototransistors (PTs) are crucial for integrating light detection with signal amplification, leveraging the photogating effect to modulate channel conductance by adjusting the charge carrier density in the active channel of field-effect transistors (FETs) under illumination ^[1,2].<br/>Hybrid material phototransistors, combining inorganic and organic components, achieve enhanced sensitivity and efficiency due to the high carrier mobility of inorganic materials and the excellent light absorption and adjustable bandgap of organic materials ^[3,4]. Conjugated Poly(3-hexylthiophene) (P3HT) is widely utilized in optoelectronics owing to its flexibility, high absorption coefficient, and cost-effectiveness, while carbon nanotubes (CNTs) are notable for their superior electrical and optical properties derived from their one-dimensional structure ^[5]. The low-temperature, solution-processable nature of CNT and P3HT composites makes them ideal for a range of cutting-edge, low-cost, flexible, and large-area light detection applications. These include process monitoring, biomedical imaging, night vision, and wearable electronics, which benefit from diverse printing techniques such as spray coating, screen printing, aerosol jet printing, inkjet printing, and layer-by-layer assembly ^[6-8].<br/>In this study, we present a simplified and cost-effective process for fabricating bilayer CNT/P3HT ink-based phototransistors using aerosol jet printing. We aim to investigate their potential in high-responsivity printed optical detection devices, with a focus on further optimization and scalability for printed and flexible electronics applications.<br/>Our findings reveal that the printed devices exhibit exceptionally high photoresponsivity, achieving 1.57 x 10³A/W under forward bias and 5.23 x 10⁴ A/W under reverse bias at a wavelength of 470 nm. This remarkable photoresponsivity is primarily due to the high light absorption characteristics of the conjugated polymer, combined with the excellent mobility provided by the underlying CNT network. Furthermore, we assessed the device's detectivity by analyzing its noise profile at 10 Hz across various V_GS values. The device's maximum detectivity reaches approximately 6.22 x 10⁸ Jones under forward bias and 2.05 x 10¹⁰ Jones under reverse bias. These results indicate that the aerosol jet-printed P3HT/semi-CNT bilayer platform is a promising approach for advanced large-area, flexible photodetection applications.<br/><br/>1. Huang, X., Ji, D., Fuchs, H., Hu, W. & Li, T. Recent Progress in Organic Phototransistors: Semiconductor Materials, Device Structures and Optoelectronic Applications. ChemPhotoChem <b>4</b>, 9–38 (2020).<br/>2. Tavasli, A., Gurunlu, B., Gunturkun, D., Isci, R. & Faraji, S. A Review on Solution-Processed Organic Phototransistors and Their Recent Developments. Electronics 2022, Vol. 11, Page 316 <b>11</b>, 316 (2022).<br/>3. Zhu, H. et al. Perovskite and conjugated polymer wrapped semiconducting carbon nanotube hybrid films for high-performance transistors and phototransistors. ACS Nano <b>13</b>, 3971–3981 (2019).<br/>4. Chang, P. H. et al. Ultrahigh Responsivity and Detectivity Graphene–Perovskite Hybrid Phototransistors by Sequential Vapor Deposition. Scientific Reports 2017 7:1 <b>7</b>, 1–10 (2017).<br/>5. Kufer, D. & Konstantatos, G. Photo-FETs: Phototransistors Enabled by 2D and 0D Nanomaterials. ACS Photonics <b>3</b>, 2197–2210 (2016).<br/>6. Roslan, N. A., Abdullah, S. M., Haliza, W., Majid, A. & Supangat, A. Investigation of VTP:PC 71 BM organic composite as highly responsive organic photodetector. Sensors and Actuators A <b>279</b>, 361–366 (2018).<br/>7. Park, J. B. et al. Visible-Light-Responsive High-Detectivity Organic Photodetectors with a 1 μm Thick Active Layer. ACS Appl Mater Interfaces <b>10</b>, 38294–38301 (2018).<br/>8. LaRiviere, B.A., Groth, P.W., Joshi, P.C. and Ericson, M.N., 2023. An Optical Aerosol Sensor for Process Monitoring of Aerosol-Jet Printing. IEEE Access.