Jia-Chong Ho

High-performance bottom-contact devices based on an air-stable n-type organic semiconductor N,N-bis (4-trifluoromethoxybenzyl)-1,4,5,8-naphthalene-tetracarboxylic di-imide

N,N-bis(4-trifluoromethoxybenzyl)-1,4,5,8-naphthalene-tetracarboxylic di-imide was applied to organic semiconductors for bottom-contact thin-film transistors. The carrier mobility was 1.6×10−2cm2V−1s−1, the threshold voltage (VT) was +5.5V, and the on/off current ratio was 8.6×105. Devices without any further surface treatments were tested in an ambient environment. The threshold voltage shift (ΔVT) was verified by gate bias stress measurements. A prototype compound, N,N-bis(4-trifluoromethylbenzyl)naphthalene-1,4,5,8-tetracarboxylic di-imide, shows direct correlation to the bottom-contact device with the varied molecular structure.

Enhanced Performance of Benzothieno[3,2‐b]thiophene (BTT)‐Based Bottom‐Contact Thin‐Film Transistors

Three new benzothieno[3,2-b]thiophene (BTT; 1) derivatives, which were end-functionalized with phenyl (BTT-P; 2), benzothiophenyl (BTT-BT; 3), and benzothieno[3,2-b]thiophenyl groups (BBTT; 4; dimer of 1), were synthesized and characterized in organic thin-film transistors (OTFTs). A new and improved synthetic method for BTTs was developed, which enabled the efficient realization of new BTT-based semiconductors. The crystal structure of BBTT was determined by single-crystal X-ray diffraction. Within this family, BBTT, which had the largest conjugation of the BTT derivatives in this study, exhibited the highest p-channel characteristic, with a carrier mobility as high as 0.22 cm(2)  V(-1)  s(-1) and a current on/off ratio of 1×10(7) , as well as good ambient stability for bottom-contact/bottom-gate OTFT devices. The device characteristics were correlated with the film morphologies and microstructures of the corresponding compounds.

54.1: Invited Paper: A Novel Approach to Make Flexible Active Matrix Displays

A flexible thin film transistor (TFT) backplane was successfully developed with Polyimide (PI) substrate and a novel de-bonding technology. The PI is colorless and transparent which can sustain a process temperature of 200°C. with this progress, flexible organic light emitting diode (OLED) and electrophoretic display (EPD) can readily be integrated with flexible TFT backplane to fabricate flexible AMOLED and flexible AMEPD.

45.3: Pentacene Organic Thin-Film Transistor Integrated with Color Twisted Nematic Liquid Crystals Display (CTNLCD)

Pentacene Organic Thin-Film Transistor (OTFT) integrated with Color Twisted Nematic Liquid Crystals Display (CTNLCD) has been developed. This display used photolithography, pentacene deposition, color filter and TNLC. In addition, we successfully develop the OTFT passivation layer process to avoid the damage of TNLC. Above these processes are integrated to manufacture the 3 inch CTNLCD panels with 64 ×128 pixels.

Enhanced performance of solution-processed TESPE-ADT thin-film transistors.

A solution-processed anthradithiophene derivative, 5,11-bis(4-triethylsilylphenylethynyl)anthradithiophene (TESPE-ADT), is studied for use as the semiconducting material in thin-film transistors (TFTs). To enhance the electrical performance of the devices, two different kinds of solution processing (spin-coating and drop-casting) on various gate dielectrics as well as additional post-treatment are employed on thin films of TESPE-ADT, and p-channel OTFT transport with hole mobilities as high as ~0.12 cm(2) V(-1) s(-1) are achieved. The film morphologies and formed microstructures of the semiconductor films are characterized in terms of film processing conditions and are correlated with variations in device performance.

Photoluminescence Study on Threading Dislocation in GaN Revealed by Selective Photoelectrochemical Etching

Selective etching was studied between the crystalline GaN and its dislocations by controlling the KOH concentration and the ult raviolet photon intensity in photoelectrochemical (PEC) etching. The PEC etching rate of GaN is governed by the density of photogenerated carriers and the direct chemical reaction between GaN and the electrolyte. The dislocation is more chemically reactiv e than crystalline GaN, whereas crystalline GaN has a higher density of the photogenerated minority carrier than the threading dis location. By using the selective etching method, the origin of photoluminescence (PL) from the near bandedge of crystalline GaN and dislocations could be clarified. The room-temperature PL peak at 3.41 eV is due to the emission from the crystalline GaN an d the peak at 3.35 eV is attributed to the threading dislocation.

43.3: A Novel Flexible AMOLED with Touch Based on Flexible Universal Plane for Display Technology

A flexible thin film transistor (TFT) backplane, OLED, and the flexible projective capacitive touch sensing film were successfully developed and integrated with colorless and transparent Polyimide (PI) substrate for the first flexible touch AMOLED display based on the flexible universal plane for display (FlexUPD) technology. This unique substrate handling technology is not only compatible with the current TFT manufacturing facilities but also allows us to use the same design rule of TFT backplane as that on the glass.

Performance of Organic Thin-Film Transistors Controlled by Electrode and Device Structures

We have fabricated organic thin-film transistors (OTFTs) of top contact (TC) structures using silver electrode based on triethylsilylethynyl anthradithiophene (TES-ADT) with mobility above 0.41 cm2 s-1 V-1, current modulation higher than 5 times 107 and sub-threshold swing below 0.65 V/dec. The electrical characteristics of OTFTs are not only corresponding to the work function of source and drain electrodes materials but also to the surface tension and deposition energy of them. The effects of work function and surface tension dominate the electrical characteristics in bottom contact (BC) device. On the other hand, TC device is affected by deposition energy dominantly.

Bottom-Contact n-Channel Organic Thin-Film Transistors with Naphthalene-Based Derivatives

We investigated bottom-contact organic thin-film transistors based on n-benzyl naphthalene 1,4,5,8-tetracarboxylic diimides. The electrical characteristics were tested in both air and vacuum environments. n-Type semiconductors which are modified by fluorinated imide can be operated in ambient environment. The close packing of the fluorinated ester imide group leads to carrier mobility as high as 1.6 X 10 -2 cm 2 V -1 s -1 . The short distance between each molecule can be found via a single-crystal structure.

P‐21: Stability and Integrability Evaluation of Organic Thin Film Transistor with Solution Processable Semiconductor

We demonstrate Organic thin film transistors (OTFTs) with solution-processed semiconductor, triethylsilylethynyl anthradithiophene (TES-ADT), as the active layer materials are investigated. Bottom-gate solution-processed TES-ADT OTFTs possess excellent performance with mobility of 0.05 cm2V−1s−1, current modulation of 4×106, sub-threshold slope of 0.91 V/dec. and threshold voltage of −7.7 V on glass substrate. The reliability of device is evaluated and demonstrates good electrical performance uniformity and stability after bias stress. Particularly, the devices exhibit reversible degradation after vacuum annealing, shown its environmental stability under air atmosphere. Moreover, the device integrability has been demonstrated with two transistors-one capacitor (2T1C) array for display media driving such as organic light emitting diode (OLED).