Fabrication of Two-Dimensional Crystalline Organic Films by Tilted Spin Coating for High-Performance Organic Field-Effect Transistors

Abstract

We developed a facile method for fabricating large-area, two-dimensional (2D), organic, highly crystalline films and extended it to organic thin-film transistor arrays. Tilted spinning provided oriented flow at the three-phase contact line, and a 2D crystalline film that consisted of layer-by-layer stacked 2,7-diocty[1]­benzothieno­[3,2-b]­benzothiophene (C8-BTBT) was obtained facilely for organic thin-film transistors (OTFTs). The extracted field-effect mobility is 4.6 cm2 V–1 s–1, but with nonideal features. By applying this method to microdroplet arrays, an oriented crystal was fabricated, and the channel region for OTFTs was covered by adjusting the spinning speed. By tuning the tilt angle (θ) of the revolving substrate, we fabricated high-performance OTFT arrays with average and maximum mobilities of 7.5 and 10.1 cm2 V–1 s–1, respectively, which exhibited high reliability factors of over 90% and were close to that of ideal transistors. These results suggest that high-quality crystalline films can be obtained via a facile tilted-spinning method.

Crystal Orientation Imaging of Organic Monolayer Islands by Polarized Light Microscopy

“…The confirmation of crystal orientation in bulk or thin-films was performed by X-ray diffraction, 3,[7][8][9][10][11][12][13][14][15][16] low-energy electron diffraction (LEED), [17][18][19] photoemission electron microscopy, 20 optical measurements, 2,[14][15][16][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38] and atomic force microscopy (AFM). 2,30,[39][40][41][42][43] For small molecule organic materials that are soluble in organic solvents, X-ray diffraction measurement and absorption spectroscopy 2,15,16,21,22 have been used to investigat...…”

“…2,23,33 However, the preparation of thin films composed of insoluble organic materials is currently limited to vacuum deposition, which produces polycrystalline thin films. To investigate these polycrystalline organic thin films, a spatially resolved microscopic measurement 2,14,15,[17][18][19][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40][41][42][43] is useful to reveal the orientation of individual grains in the polycrystalline film. The crystal orientation of organic polycrystalline thin films has been investigated by microbeam LEED [17][18][19] and atomic force microscopy in transvers shear microscopy (TSM) in AFM measurements, 2,30,[39][40][41][42][43] which require to perform measurements in vacuum and/or long-time measurements.…”

Recent Advances in Flexible Organic Synaptic Transistors

“…The proposed OCSC is very promising for the future fabrication of FOSTs. In another example, Liu et al [162] developed highquality crystalline films via a facile tilted-spinning method. During the spin-coating process, the solution concentration, rotation speed, spin-coating time, and sample position will have an important effect on the film formation.…”

Layer‐By‐Layer Printing Strategy for High‐Performance Flexible Electronic Devices with Low‐Temperature Catalyzed Solution‐Processed SiO2

“…[8,9] In this case, photolithography is incompatible with some organic semiconductors, and thus leading to a challenging issue in the fabrication of flexible devices. [10][11][12][13][14][15] In comparison to photolithography process, solution-processing technique, like additive printing, can be employed to pattern electronic structures with several benefits such as easy to scale up, the feasibility to various devices and low manufacturing cost. [16,17] The printing processes used for fabricating electronics can be implemented under ambient atmosphere at room temperature without utilization of thermal post-treatment, thereby leading to the roll-to-roll production of flexible biosensors, solar cells, and integrated circuits when associating with opt-electronic semiconductors or functional composites.…”