Patternable Solution‐Crystallized Organic Transistors with High Charge Carrier Mobility

Abstract

Development of high-performance printed semiconductor devices is highly desired with the expectation for the nextgeneration technologies of "printable electronics" providing simply fabricated, fl exible, large-area, low-cost, and environmentally friendly electronic products such as paper-like fl exible displays. Patterned arrays of printed organic fi eld-effect transistors (OFETs) based on chemically stable solutionprocessed organic semiconductors are regarded as key devices that operate as fundamental switching components in, for example, pixel-controlling active-matrix elements. However, performance of conventional solution-coated noncrystal organic thin-fi lm transistors has yet to be improved for practical use in general electronic circuitry. Here, newly developed arrays of patterned crystalline OFETs of air-stable compound 2,9-didecyl-dinaphtho[2,3-b:2',3'-f ]thieno[3,2-b]thiophene (C 10 -DNTT) formed from hot solution are presented. A method of oriented growth is introduced to provide the singlecrystalline fi lms of C 10 -DNTT that regulates the crystallizing direction and positions in a single process. The benchmark value, 10 cm 2 V − 1 s − 1 , of the charge mobility is achieved for the present OFETs, far exceeding the performance of former devices and opening a practical way to realize printed and fl exible electronics with suffi cient switching speed. The result is attributed to almost perfect molecular periodicity in the crystal fi lms, which allows effective intermolecular charge transport of the electrons.In the process of forming organic semiconductor fi lms from solution by naturally evaporating the solvent near room temperature, constituent molecules that are independently dispersed in the solvent, are expected to self-organize into a highly ordered assembly with the amazing speed of more than 10 10 molecules per second. [ 1 ] Since the speed of the fi lm growth is directly translated to high-throughput production, solution techniques such as spin-coating and drop-casting are very attractive for the industry. [ 2 ] Regarding the performance of the solution-processed organic fi eld-effect transistors (OFETs), their switching speed is directly determined by charge carrier mobility in the organic semiconductors, which relies on microscopic electronic properties of molecule-to-molecule charge-transfer probability and the extent of molecular ordering. Therefore, it has been intensively challenging to create high-mobility active semiconductor layers using simple solution techniques. In addition, simple methods of forming their patterned arrays during the fi lm growth have been regarded as essential technology for accelerated production of matrix devices. Here, the extent of the molecular order signifi cantly infl uences device performance through the charge carrier mobility in the semiconductor fi lms. In order to realize much higher performance than achieved in present devices, synthesis of functional π -conjugated molecules with superior selfassembling properties, in addition to their high-charge-trans...

Arrays of Pentacene Single Crystals by Stencil Evaporation

“…8 As a result, the growth of high-density arrays of organic single crystals is a desirable semiconductor film topology to achieve arrays of highperformance organic TFTs that can be exploited in large-area flexible circuits such as display backplanes. [9][10][11][12] Among different film deposition techniques, evaporation provides high material purity along with controlled thickness and uniformity over large areas. 3 The vapor phase growth of single organic crystals is traditionally performed by physical vapor transport (PVT) in process conditions close to thermodynamics equilibrium.…”

Theoretical Investigation on Charge Transfer Properties of 1,3,5-Tripyrrolebenzene (TPB) and its Derivatives with Electron-withdrawing Substituents

“…[1][2][3][4] The charge mobility of several kinds of OSC is now as large as 10 cm 2 ·V -1 ·s -1 in the thin films and single crystals [5][6][7][8][9][10] such as pentacene. But there are still some unsolved problems.…”

Large-area formation of self-aligned crystalline domains of organic semiconductors on transistor channels using CONNECT

“…To address the above challenges, various groups have developed methods to pattern OSCs (3,9,(13)(14)(15)(16)(17)(18)(19)(20)(21)(22)(23)(24), such as templating OSCs (14,(19)(20)(21), inkjet printing (9,18), gravure printing, and other roll-to-roll coating methods (25)(26)(27). In addition, the use of solvent wetting/dewetting surface treatments has been widely used in conjunction with the patterning methods described above (10, 11, 13, 15-17, 22, 28, 29).…”

“…For instance, alignment using inkjet printing is restricted by the registration capability of the instrument, whereas the size of each OTFT is limited by the droplet size attainable (22,31). Another potential issue with these methods is the variance in electrical characteristics of TFTs due to the difficulty in obtaining uniform crystal growth on isolated TFTs over large areas (9,15,21,27,28,(31)(32)(33)(34)(35). Even single crystalline domains of patterned TFTs may have large variability in electrical characteristics as a result of random orientation and size variance.…”