Solution-Processed Organic Thin-Film Transistor Arrays with the

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Solution Processed Organic Thin Film Transistor Arrays with Assistance of Laser Ablation Huihuang Yang, Cihai Chen, Guocheng Zhang, Shuqiong Lan, Huipeng Chen, and Tailiang Guo ACS Appl. Mater. Interfaces, Just Accepted Manuscript • DOI: 10.1021/acsami.6b14813 • Publication Date (Web): 12 Jan 2017 Downloaded from http://pubs.acs.org on January 16, 2017

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ACS Applied Materials & Interfaces

Solution Processed Organic Thin Film Transistor Arrays with Assistance of Laser Ablation Huihuang Yang,1Cihai Chen,1 Guocheng Zhang,1,2Shuqiong Lan,1 Huipeng Chen,1* Tailiang Guo1 1

Institute of Optoelectronic Display, National & Local United Engineering Lab of Flat Panel Display Technology, Fuzhou University, Fuzhou 350002, China Email: [email protected] 2 College of Information Science and Engineering, Fujian University of Technology, Fuzhou 350108, China Abstract A key step toward commercialization of OTFT is to manufacture large-area OTFT arrays with desired uniform device performance. In this work, for the first time, solution processed organic thin film transistor (OTFT) arrays were fabricated with assistance of laser ablation. The source-drain electrodes and the whole devices were patterned by precise control of laser intensity and process path. Compared with traditional methods, this approach significantly simplifies the fabrication process of OTFT arrays with high quality and high yield. A careful selection of laser processing parameters is key to obtain high quality and high performance OTFT arrays. The grazing incidence x-ray diffraction experiments and device performance tests ensured the selection of proper laser ablation intensity. Eventually, the OTFT arrays on silicon wafer and ITO glass exhibited uniform electrical characteristics with the mean mobility of 0.16 and 0.10 cm2V-1s-1, respectively. These results demonstrated that laser ablation process provides a promising tool to simplify the fabrication of solution processed OTFT arrays with low cost and high yield, which has great potential in upscaling of high performance OTFT arrays for display and circuits. 1

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Keywords: Organic thin film transistor, TFT arrays, Laser ablation, Solution processed, Display and circuits 1. Introduction Organic thin film transistors (OTFT), as switching and driving basic devices, are widely used in display, sensors, memory, and have experienced rapid development in the past several decades. With the extensive efforts attributed to the research on materials, interface engineering, and charge transport, the factors which limit device performance are being rapidly overcome. Due to its attractive advantages, including extensive organic materials, low temperature process, and simple manufacture technology, OTFTs are comparable to conventional inorganic TFTs for commercial applications. Now a key step toward commercialization of OTFT is to manufacture large-area OTFT arrays with desired uniform device performance, especially for display and circuits. Unfortunately, most reports in OTFT are focused on the non-patterned single TFT from spin coating. Therefore, in order to fabricate OTFT arrays, directing writing printing techniques, inkjet printing, spray printing, and screen printing has been reported for the fabrication of OTFT arrays.1-6Among these printing techniques, Inkjet printing technology is considered as a prominent printing technology to fabricate OTFT arrays.7-10 Unfortunately, the presence of coffee-ring effect, which is even amplified after thermal annealing, often results in the uneven deposition of functional materials during the inkjet process.11-13 Additionally, larger particles or viscous solutions were formed due to the aggregation of polymer chains, which blocked the nozzle of the 2


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inkjet printers.14 Furthermore, most of the previous work used the vacuum thermal evaporation to fabricate drain-source electrodes, which increased the process complexity and cost. Therefore, solution processed drain-source electrodes would simplify the process and reduce the cost. An alternative approach to realize OFET arrays is transfer printing such as microcontact and microtransfer printing, gravure printing, and offset printing.1,15-17 The shortcomings of the these printing process include: high printing press setup costs, long lead time for cylinder preparation, and time associated with producing specific plates compared to directing writing printing. Laser-induced forward transfer (LIFT), sometimes called laser printing, is one of transfer printing techniques which allows to transfer the film from the donor substrate to the acceptor substrate with the pulsed laser beam. The use of LIFT for the fabrication of OTFTs has been successfully realized.18-21 However, The disadvantage of LIFT is that the entire process depends on the optical properties of the transferred material. Thus the transferred materials must have high absorption at the laser wavelength, which limits the choice of materials. Moreover, as high energy beam is required for the transfer of the film, appropriate measures, for instance metallic sacrificial layer, must be taken to avoid the laser damage to the semiconductor layer.19,22 Laser ablation is another promising technique in the field of laser processing technology. It has been widely used for the fabrication of inorganic, organic and hybrid devices such as solar cell modules, photodetectors, and stretchable dielectric elastomer and sensors.23-27 Laser ablation is also used to process components of the photoelectronic devices such as the synthesis 3



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of In2O3 nanowire mats, and titania nanoparticles.28,29 Unfortunately, laser ablation has never been used to fabricate the OTFT arrays. In this work, we therefore report solution processed OTFT arrays on silicon wafer and ITO glass with assistance of laser ablation. To be best of our knowledge, this is the first paper to report solution processed OTFT arrays with assistance of laser ablation. Compared with traditional methods, this approach significantly simplifies the fabrication process of OTFT arrays with high quality and high yield.

High

patterning resolution can be realized by the precise control of laser intensity and ablation path. Meanwhile, high processing speed and high precision patterning improves the yield of device production, and decreases the variation of device performance. Eventually, the OTFT arrays exhibit sufficiently uniform electrical characteristics with the mean mobility of 0.16 and 0.10 cm2V-1s-1, for Si and ITO substrate respectively. These results demonstrated that laser ablation is a promising tool for the realization of OTFT arrays and has great potential to be applicable in display and circuits. 2. Experiments 2.1 Materials Poly[2,5-bis(alkyl)pyrrolo[3,4-c]pyrrole-1,4(2H,5H)-dione-alt-5,5´di(thiophen-2-yl)-2,2´-(E)-2-(2-(thiophen-2-yl)vinyl)-thiophene](PDVT-8) (Mw=50K, PDI=2.4) was purchased from 1-Materials, which is a typical high mobility polymer semiconductor with good stability.30-32 PDVT-8 was dissolved in chlorobenzene at 80°C for to prepare 10 mg/ml solution. Poly(4-vinylphenol)(PVP)(Mw 25,000), 4


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4,4′-(Hexafluoroisopropylidene)diphthalic anhydride(HAD)( 99%) and Propylene glycol monomethyl ether acetate(PGMEA)( ≥99.5%) were purchased from Sigma-Aldrich. PVP and HAD were mixed in PGMEA solution with weight ratio of 10:1 and then stirred overnight before spin coating. Jet-605c conductive nanosilver ink was purchased from Kunshan Hisense electronics Co.Ltd. PVP:HAD solution and nanosilver ink are typical used for the solution processed dielectric layer and electrodes, respectively.33-35 Moreover, the low sintering temperature of nanosilver ink avoids the damage to semiconductor layer, which is crucial for the OTFT fabrication. 2.2 Laser Ablation Laser ablation processes were performed with the 4th generation redENERGY® pulsed product platform (SPI laser, UK). Figure 1a schematically shows our laser ablation setup for the fabrication of OTFT devices. The system can operate at limited pulse repetition frequency of up to 500 kHz with pulse width as short as 15 ns. A maximum power of 20 W at the wavelength of 1064 nm is available. Nanosecond pulsed laser with wavelength of 1064 nm is typical used for the ablation of ITO and silver.36-38 The beam quality at 1064 nm reaches M2

Solution-Processed Organic Thin-Film Transistor Arrays with the

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