C8 BTBT薄膜结晶形貌及OTFT器件性能研究

以p型共轭有机小分子2,7二辛基[1]苯并噻吩并[3,2‐b]苯并噻吩(C8‐BTBT)作为底栅顶接触有机薄膜晶体管(OTFT)的有源层,采用浸渍提拉法、喷墨打印法和真空蒸镀法三种制备工艺,探究半导体薄膜载流子迁移率与结晶形貌的关系,发现不同工艺下有机小分子呈现出不同的生长行为和结晶情况,在很大程度上决定了OTFT器件性能的优劣;此外,通过XRD分析研究了退火处理对C8‐BTBT结晶的影响。结果表明,真空蒸镀制备的薄膜具有更高的结晶度、衬底覆盖率高,并且呈现出SK(Stranski‐Krastanov)模式的结晶生长特征,相应器件中陷阱密度最低,迁移率高达5.44 cm^2·V^-1·s^-1,开关比超过106;且退火处理会严重破坏C8‐BTBT薄膜的结晶。因此,控制半导体层的生长行为,提升半导体层的覆盖率和结晶度是制备高性能共轭小分子OTFT器件的有效途径。     

Pressure Control Organic Vapor Deposition Methods for Fabricating Organic Thin‐Film Transistors

In this letter, we report on the development progress of a pressure control organic vapor deposition (PCOVD) technology used to design and build a large area deposition system. We also investigate the growth characteristics of a pentacene thin film by PCOVD. Using the PCOVD method, the mobility and on/off current ratio of an organic thin‐film transistor (OTFT) on a plastic substrate are 0.1 cm²/Vs and 10⁶, respectively. The developed OTFT can be applied to a flexible display on a plastic substrate.     

Pentacene bottom-contact thin film transistors with solution-processed BZT gate dielectrics

The solution-processed high-k barium zirconate titanate (BZT) as gate dielectrics for bottom-gate pentacene-based organic thin film transistor (OTFT) applications is presented. To reduce the transistor threshold voltage, higher work function metals (Au) is used as the gate electrodes. The threshold voltage is efficiently decreased from −3.6 to −2.15 V as compared to that of Al. In addition, the UV/ozone was employed to treat the Au (source/drain) surface to improve the poor crystalline of pentacene grown on Au. Moreover, the surface morphologies and orientations of pentacene films were analyzed through atomic force microscopy (AFM) and X-ray diffraction. As the results, the stack of pentacene molecules from disorder state changed to vertical growth on the Au surface. Finally, the electrical properties of pentacene-based thin film transistors exhibit high field-effect mobility of 4.5 cm²/V·s, low subthreshold swing of 260 mV/decade, high on/off ratio of 1.4 × 10⁵ and low operation voltage of −5 V. These results are better than the reported data using bottom contact pentacene OTFTs.     

有机薄膜晶体管支撑平板显示技术进步

目前有机薄膜晶体管（OTFT）的综合性能已经达到商用非晶硅的水平,其低生产成本和高功能等优点已显示出巨大的市场潜力和产业化价值。本文从技术特征、实用化的发展情况和动态特性等方面介绍了有机薄膜晶体管。有机薄膜晶体管将很快成为新一代平板显示的核心技术。     

有机薄膜晶体管(OTFT)的研究进展

有机薄膜晶体管(organic thin film transistor,OTFT)具有工艺简单、成本低及柔韧性良好等优点,成为下一代显示技术的研究焦点.本文综述了有机薄膜晶体管的研究现状和未来的发展趋势,比较了采用不同材料的OTFT器件的性能,总结了影响OTFT性能的两大主要因素,即栅极绝缘层与有机有源层之间的界面特性和有机有源层与源/漏电极之间欧姆接触电阻的大小,并详细综述了改善OTFT性能的最新方法和研究成果.     

High-performance 2,9-DPh-DNTT organic thin-film transistor by weak epitaxy growth method

2,9-DPh-DNTT, an isomeric of diphenyl-dinaphtho[2,3-b:2′,3′-f]-thieno[3,2-b] thiophene (DPh-DNTTs), is an emerging candidate of high mobility organic semiconductor material. In this work, a high performance 2,9-DPh-DNTT organic thin-film transistor (OTFT) is fabricated by the method of weak epitaxy growth. The quality of 2,9-DPh-DNTT thin film was significantly improved when its epitaxial layer grows on an inducing layer of para-sexiphenyl (p-6P). Continuous large-area, highly ordered and terraced 2,9-DPh-DNTT polycrystalline thin films are obtained. The hole mobility of as-fabricated 2,9-DPh-DNTT thin-film transistor reaches up to 6.4 cm² V⁻¹s⁻¹. This simple process of preparing high mobility 2,9-DPh-DNTT thin-film transistor supplies a facile route of large-area OTFT fabrication.     

喷墨印刷制备有机薄膜晶体管及其电路的研究进展

有机薄膜晶体管在大面积柔性显示、柔性电子存储等方面具有广阔的潜在应用前景。喷墨印刷技术由于具有工艺简单、成本低廉、微图形数字化、与柔性衬底兼容等优点而成为一种有效的制造有机电子器件工艺方法。文章综述了近年来基于喷墨印刷技术制备有机薄膜晶体管的研究进展,探讨了在制造过程中存在的问题。     

Transparent Nanopaper‐Based Flexible Organic Thin‐Film Transistor Array

Eco‐friendly and low‐cost cellulose nanofiber paper (nanopaper) is a promising candidate as a novel substrate for flexible electron device applications. Here, a thin transparent nanopaper‐based high‐mobility organic thin‐film transistor (OTFT) array is demonstrated for the first time. Nanopaper made from only native wood cellulose nanofibers has excellent thermal stability (>180 °C) and chemical durability, and a low coefficient of thermal expansion (CTE: 5–10 ppm K^‐1). These features make it possible to build an OTFT array on nanopaper using a similar process to that for an array on conventional glass. A short‐channel bottom‐contact OTFT is successfully fabricated on the nanopaper by a lithographic and solution‐based process. Owing to the smoothness of the cast‐coated nanopaper surface, a solution processed organic semiconductor film on the nanopaper comprises large crystalline domains with a size of approximately 50–100 μm, and the corresponding TFT exhibits a high hole mobility of up to 1 cm²V^‐1 s^‐1 and a small hysteresis of below 0.1 V under ambient conditions. The nanopaper‐based OTFT also had excellent flexibility and can be formed into an arbitrary shape. These combined technologies of low‐cost and eco‐friendly paper substrates and solution‐based organic TFTs are promising for use in future flexible electronics application such as flexible displays and sensors.     

Self-aligned flexible organic thin-film transistors with gates patterned by nano-imprint lithography

Many applications that rely on organic electronic circuits still suffer from the limited switching speed of their basic elements – the organic thin film transistor (OTFT). For a given set of materials the OTFT speed scales inversely with the square of the channel length, the parasitic gate overlap capacitance, and the contact resistance. For maximising speed we pattern transistor channels with lengths from 10 μm down to the sub-micrometre regime by industrially scalable UV-nanoimprint lithography. The reduction of the overlap capacitance is achieved by minimising the source–drain to gate overlap lengths to values as low as 0.2 μm by self-aligned electrode definition using substrate reverse side exposure. Pentacene based organic thin film transistors with an exceptionally low line edge roughness <20 nm of the channels, a mobility of 0.1 cm²/Vs, and an on–off ratio of 10⁴, are fabricated on 4″ × 4″ flexible substrates in a carrier-free process scheme. The stability and spatial distribution of the transistor channel lengths are assessed in detail with standard deviations of L ranging from 185 to 28 nm. Such high-performing self-aligned organic thin film transistors enabled a ring-oscillator circuit with an average stage delay below 4 μs at an operation voltage of 7.5 V.     

Growth of Large Crystalline Grains of Vanadyl‐Phthalocyanine without Epitaxy on Graphene

The performance of organic semiconductor thin films in electronic devices is related to their crystal structure and morphology, with charge transport mobility dependent on the degree of crystallinity and on the crystallographic orientation. Here organic molecular beam deposition of vanadyl phthalocyanine is studied on graphene and it is shown that crystalline grains up to several micrometers across can be formed at substrate temperatures of 155 °C, compared to room temperature grain sizes of ≈30 nm. Transmission electron microscopy confirms the presence of long range order at elevated substrate temperatures and reveals that the molecules are stacked in an edge‐on orientation, but are not epitaxially aligned to the graphene. The crystalline grain sizes are significantly larger on graphene than on disordered substrates such as graphene oxide and silicon oxide. The effect on charge transport is probed by conducting atomic force microscopy, with the high temperature films on graphene showing increased mobility and uniformity and decreased trap density. These results illustrate an important advantage for the integration of graphene electrodes with organic semiconductor devices: the homogeneous surface of graphene results in high diffusion and low nucleation rates for thin film growth, encouraging the formation of highly crystalline films even with nonepitaxial growth.     

异质诱导生长的酞菁铜薄膜晶体管的研究

因酞菁薄膜平面具有多电子共轭大π键结构,本文采用异质诱导的方式对酞菁薄膜的生长特性进行了改善研究。采用高掺杂硅为栅极,氧化硅为绝缘层,生长α-四噻吩或p-六联苯薄膜为异质诱导层,制备了酞菁铜有机薄膜晶体管。利用原子力显微镜研究薄膜生长特性,并对比研究了2种诱导层对薄膜晶体管性能的影响。实验结果表明:α-四噻吩上生长的酞菁铜薄膜,形貌呈片状,而p-六联苯上生长的酞菁铜薄膜,形貌呈针状,均与单层酞菁铜棒状形貌不同。同时,α-四噻吩与p-六联苯薄膜上生长酞菁铜后,两者晶体管电性能都有不同程度的提高,均比单层酞菁铜提高了1~2个数量级,表明α-四噻吩或p-六联苯对酞菁铜薄膜均有诱导效应,可以获得高性能的有机薄膜晶体管。     

Organic Tribotronic Transistor for Contact‐Electrification‐Gated Light‐Emitting Diode

Tribotronics is a new field about the devices fabricated using the electrostatic potential created by contact electrification as a “gate” voltage to tune/control charge carrier transport in semiconductors. In this paper, an organic tribotronic transistor is proposed by coupling an organic thin film transistor (OTFT) and a triboelectric nanogenerator (TENG) in vertical contact‐separation mode. Instead of using the traditional gate voltage for controlling, the charge carrier transportation in the OTFT can be modulated by the contact‐induced electrostatic potential of the TENG. By further coupling with an organic light‐emitting diode, a contact‐electrification‐gated light‐emitting diode (CG‐LED) is fabricated, in which the operating current and light‐emission intensity can be tuned/controlled by an external force–induced contact electrification. Two different modes of the CG‐LED have been demonstrated and the brightness can be decreased and increased by the applied physical contact, respectively. Different from the conventional organic light‐emitting transistor controlled by an electrical signal, the CG‐LED has realized the direct interaction between the external environment/stimuli and the electroluminescence device. By introducing optoelectronics into tribotronics, the CG‐LED has open up a new field of tribophototronics with many potential applications in interactive display, mechanical imaging, micro‐opto‐electro‐mechanical systems, and flexible/touch optoelectronics.     

Photo‐Stable Organic Thin‐Film Transistor Utilizing a New Indolocarbazole Derivative for Image Pixel and Logic Applications

Small molecule pentacene layer has been a representative among many organic thin‐film transistor (OTFT) channels with decent p‐type mobilities, but it is certainly light‐sensitive due to its relatively small highest occupied molecular orbital‐lowest unoccupied molecular orbital (HOMO‐LUMO) gap (1.85 eV). Although a few other small molecule‐based layers have been reported later, their photo‐stabilities or related device applications have hardly been addressed. Here, a new photostable organic layer is reported, heptazole (C₂₆H₁₆N₂), which has almost the same HOMO level as that of pentacene but with a higher HOMO‐LUMO gap (≈2.95 eV). This heptazole OTFT displays a decent mobility comparable to that of conventional amorphous Si TFTs, showing good photostability unlike pentacene OTFTs. An image pixel driving the photostable heptazole OTFT connected to a pentacene/Al Schottky photodiode is demonstrated. This heptazole OTFT also conveniently forms a logic inverter coupled with a pentacene OTFT, sharing Au for source/drain.     

高性能钆铝锌氧薄膜晶体管的制备

本文研究并制备了钆铝锌氧薄膜和以钆铝锌氧为有源层的薄膜晶体管。钆铝锌氧薄膜材料的光致发光光谱和透过率说明钆铝锌氧薄膜在透明显示方向的应用潜力。透射电子显微镜揭示了钆铝锌氧薄膜的非晶态微观结构。钆铝锌氧薄膜晶体管显示了良好的转移特性和输出特性。器件开关比大于10~5、饱和迁移率约为10cm~2·V~(-1)·s~(-1)。实验结果表明,钆铝锌氧薄膜可用作氧化物薄膜晶体管的有源层材料;钆铝锌氧薄膜晶体管可作为像素电路的驱动器件。     

具有无机有机双绝缘层和修饰电极的薄膜晶体管

研究了有机薄膜晶体管器件.器件是以热生长的SiO2作为有机薄膜晶体管的栅绝缘层,酞菁铜作为有源层的.实验表明采用一种硅烷耦合剂-十八烷基三氯硅烷(OTS)修饰SiO2可以有效地降低栅绝缘层的表面能从而明显提高了器件的性能.器件的场效应迁移率提高了2.5倍、阈值电压降低了3 V、开关电流比从103增加到104.同时我们采用MoO3修饰铝作为器件的源漏电极,形成MoO3/Al双层电极结构.实验表明在同样的栅极电压下,具有MoO3/Al 电极的器件和金电极的器件有着相似的源漏输出电流Ids.结果显示具有OTS/SiO2双绝缘层的及MoO3/Al 电极结构的器件能有效改进有机薄膜晶体管的性能.     

Organic–inorganic hybrid materials as solution processible gate insulator for organic thin film transistors

We synthesized organic–inorganic hybrid materials (hybrimers) using a simple non-hydrolytic sol–gel reaction and applied the materials as gate insulators in organic thin film transistors (OTFTs). The hybrimer thin films had smooth and hydrophobic surfaces, and were stable with solvents. In addition, the hybrimer thin films had good electrical properties such as low leakage current and high dielectric strength. The performance of the OTFT with hybrimer gate insulator fabricated by drop casting of regioregular poly(3-hexylthiophene) (P3HT) was similar to that of OTFT with hexamethyldisilazane (HMDS) treated thermally grown SiO₂. The hysteresis of RR-P3HT based OTFT with hybrimer gate insulator was negligible.     

基于有机薄膜晶体管电特性曲线获取迁移率方法的研究

场效应迁移率是描述有机薄膜晶体管(OTFT)性能的 重要参数之一,目前OTFT场效应迁移率主要根据实验测得OTFT电特性曲线通过拟合计算方法 获得。本文针对这种方法进行深入研究发现,OTFT的场效应迁 移率与其工作状态有关。在线性工作状态下,OTFT的线性区场效应迁移率随 着 栅电压的增加而增大;在饱和工作状态下,当漏电压VD>1.5VGmax时,饱和区场效应迁移率 为一定值,表明采用此值表征OTFT的电性能更加客观和精确。     

Organic thin-film transistor sensors: Interface dependent and gate bias enhanced responses

Organic thin film transistors are a new class of sensors potentially capable of outperforming chemiresistors. They can be operated at room temperature, offer the advantage of remarkable response repeatability and can function as multi-parameter sensors. In this paper, evidence of OTFT response dependence on important parameters such as the chemical nature of the organic semiconductor active layer and the gate-dielectric/organic-semiconductor interface are produced. A sizable response enhancement of an OTFT sensor operated in the enhancement mode is also presented indicating that an OTFT can in principle lead to a lower detection limit than a resistor-type sensor with the same organic semiconductor.     

Organic thin film transistors with PMMA modified insulator

A double insulation layer structure organic thin films transistor (OTFT) was investigated for improving the performance of the SiO2 gate insulator. A 50 nm PMMA layer was coated on top of the SiO2 gate insulator as the organic insulator layer. The results demonstrated that using inorganic/organic compound insulator as the gate dielectric layer is an effective method to fabricate OTFTs with improved electric characteristics and decreased leakage current. Electrical parameters of carrier mobility and on/off ratio were calculated. OTFT based on Si substrate with a field-effect mobility of 4.0 × 10-3cm2/Vs and on/off ratio of 104 was obtained.     

Integration of silk protein in organic and light-emitting transistors

We present the integration of a natural protein into electronic and optoelectronic devices by using silk fibroin as a thin film dielectric in an organic thin film field-effect transistor (OFET) ad an organic light emitting transistor device (OLET) structures. Both n- (perylene) and p-type (thiophene) silk-based OFETs are demonstrated. The measured electrical characteristics are in agreement with high-efficiency standard organic transistors, namely charge mobility of the order of 10(-2) cm(2)/Vs and on/off ratio of 10(4). The silk-based optolectronic element is an advanced unipolar n-type OLET that yields a light emission of 100nW.