Uniaxially oriented polycrystalline thin films and air-stable n-type transistors based on donor-acceptor semiconductor (diC8BTBT)(FnTCNQ) [n = 0, 2, 4]

Abstract

We report the fabrication of high quality thin films for semiconducting organic donor-acceptor charge-transfer (CT) compounds, (diC8BTBT)(FnTCNQ) (diC8BTBT = 2,7-dioctyl[1]benzothieno[3,2-b][1]benzothiophene and FnTCNQ [n = 0,2,4] = fluorinated derivatives of 7,7,8,8,-tetracyanoquinodimethane), which have a high degree of layered crystallinity. Single-phase and uniaxially oriented polycrystalline thin films of the compounds were obtained by co-evaporation of the component donor and acceptor molecules. Organic thin-film transistors (OTFTs) fabricated with the compound films exhibited n-type field-effect characteristics, showing a mobility of 6.9 × 10−2 cm2/V s, an on/off ratio of 106, a sub-threshold swing of 0.8 V/dec, and an excellent stability in air. We discuss the suitability of strong intermolecular donor–acceptor interaction and the narrow CT gap nature in compounds for stable n-type OTFT operation.

Unidirectionally Crystallized Stable n‐Type Organic Thin‐Film Transistors Based on Solution‐Processable Donor–Acceptor Compounds

“…Low hysteresis between the forward and reverse scan in the transfer characteristics of the n = 2 device indicates the trap‐free, air‐stable characteristics of the solution‐processed films. The field‐effect mobility in the saturation regime is estimated to be 0.6 cm 2 V −1 s −1 which is one order of magnitude higher than that of the device formed by the vacuum deposition technique and is comparable to that of the single‐crystal device . Furthermore, degradation of the device characteristics was not observed over 100 h of operation under ambient conditions with a relative humidity of 65% at 293 K (Figure d), while a slight increase of hysteresis was observed in the transfer characteristics with an increase of the air‐exposure time, as represented by the increased error bar of the mobility.…”

“…Recently, a distinct class of n‐type organic semiconductors was reported with the use of charge‐transfer (CT) compounds composed of organic donor and acceptor molecules . Especially, a high degree of layer crystallinity can be achieved when 2,7‐dioctyl[1]benzothieno[3,2‐ b ][1]benzothiophene (diC 8 BTBT), a renowned single‐component organic semiconductor, is used as the donor component: In CT compounds of (diC 8 BTBT)(fluorinated derivatives of tetracyanoquinodimethane (F n TCNQ)) ( n = 0, 2, 4), a 2D semiconducting layer is formed with π‐conjugated donor and acceptor skeletons, which are separated by alkyl chain layers derived from the diC 8 BTBT end groups.…”

“…These features afford OTFTs that exhibit n‐type field‐effect characteristics with both high air stability and high thermal stability. Uniaxially oriented polycrystalline thin films were successfully produced in the compounds by using coevaporation for the component molecules . However, the use of these compounds in solution processes has not yet been investigated.…”

Multifunctional Features of Organic Charge‐Transfer Complexes: Advances and Perspectives

“…Among them, the diC 8 BTBT‐F 2 TCNQ and diC 8 BTBT‐F 4 TCNQ single‐crystal transistors showed only n‐type characteristics, while the diC 8 BTBT‐TCNQ single crystal transistors displayed ambipolar transporting property. Furthermore, the complex‐based film through vacuum co‐evaporation method exhibited air‐stable n‐type field‐effect characteristics (≈10 −2 cm 2 V −1 s −1 ) [74] . However, the diC 8 BTBT‐F 2 TCNQ thin‐film obtained through the solution‐shearing technique exhibited air‐stable n‐type operation mode with the mobility up to 0.61 cm 2 V −1 s −1 , owing to the large anisotropic alignment of the crystalline grains [75] .…”

Degradable and Dissolvable Thin-Film Materials for the Applications of New-Generation Environmental-Friendly Electronic Devices

“…Over the past two decades, there have always been new applications, which are not easy to realize with traditional electronics with inorganic semiconductors. It has resulted in pushing people to do more research on organic transistors [170,171], photovoltaic cells, energy harvester [61], light-emitting diodes [172], electronic devices [173], sensors [174], and memristors [20]. Compared with inorganic counterparts, organic technologies can address energy and cost inefficiency issues.…”