TiO2基染料敏化太阳能电池的表面修饰及性能研究

采用水热法制备TiO₂浆料,用La(NO₃)₃溶 液浸泡TiO₂薄膜获得修饰电极。用X射线光电子能谱(XPS) 和扫描电子显微镜(SEM)对修饰电极的主要成分及形貌进行表征的结果显示,电极薄膜分为 上下两层,表 面包覆层粒径较大,为La₂O₃颗粒;下层颗粒粒径较小,为TiO₂颗粒。电流-电压测 试结果显示,与修饰 前相比,用La(NO₃)₃溶液浸泡30min获得的膜电极性能最优,使 开路电压和短路电流分别提高了6.8%和 18.5%。电化学阻抗谱(EIS)测试结果表明,相同偏压下,TiO₂/La ₂O₃电极界面复合电阻比TiO₂要大,说明 La₂O₃包覆层在一定程度上抑制了界面的电子复合,改善了电池的光电化学性能。     

真空气相沉积生长PTCDI C8 N型有机薄膜晶体管

在大气环境下N型有机薄膜晶体管(OFET)的性能不稳定,为提高晶体管在大气环境稳定性,该文分别制作了SiO2单绝缘层器件和SiO2/PMMA双绝缘层器件。采用N型新材料PTCDI-C8作为有源层,Ag作为源、漏电极,对制作的不同绝缘层的器件进行聚对二甲苯的封装,对有源层进行形貌和晶体结构分析。并进行电流-电压(I-V)曲线测试。在相同工作电压下,双绝缘层器件比单绝缘层器件具有更大的场效应迁移率、开关电流比和更小的阈值电压。     

ZnPc作为有机太阳电池阴极修饰层的研究

采用ZnPc作为ZnPc/C60有机太阳电池阴极修饰层,分析了其对器件光电性能和稳定性的影响.研究了不同厚度ZnPc修饰层对器件性能的影响,结果表明用3 nm ZnPe修饰的器件性能最好.通过传输矩阵的方法画出了结构为ITO/ZnPc(30 nm)/C60(40 nm)/ZnPc(3 nm)/Al(100 nm)电池内部两束敏感光线(630 nm和450 nm光波)的光强分布图,加入3 nm ZnPc对光强分布影响不大.实验还对比分析了未添加、添加LiF和ZnPc修饰层器件的稳定性,用ZnPc修饰的器件更好地改善了稳定性,并对相关机理进行了讨论.     

阴极修饰层对ZnPc/C60有机太阳能电池性能的影响

研究了ZnPc/C60有机小分子太阳能电池阴极界面的修饰,采用LiF、Alq3和ZnPc作为修饰材料,分析不同修饰材料对器件性能和稳定性的影响。研究结果表明,引入适当厚度的修饰层不仅可以提高器件的性能,而且可以提高器件的稳定性。不同修饰材料表现出了不同的优势,用LiF修饰的器件填充因子提高了44%,Alq3修饰的器件转换效率提高了5倍,ZnPc修饰的器件开路电压最高并表现出良好的稳定性。最后,对相关机理进行了讨论。     

C60场效应晶体管的制备及修饰层对器件性能影响的研究

以重掺杂Si片作为衬底,SiOe／聚甲基丙烯酸甲酯（PMMA）为双栅绝缘层,C60为有源层,制备了不同修饰层的有机场效应晶体管（OFETs）;研究了不同修饰层的器件对于场效应性能的影响。实验表明,与未加修饰层的器件相比,经过修饰的器件性能有一定的提高,其中Alqa／LiF双修饰层器件的场效应迁移率达到最大,为1．6×1...     

基于双层界面修饰的高性能底栅底接触有机薄膜晶体管研究

一种兼容的双界面修饰被成功应用于修饰有机薄膜晶体管的底接触电极和绝缘层界面。这种兼容的双界面修饰为首先采用4-FTP修饰银源漏电极进而提高其功函数,然后采用HMDS或者OTS进一步修饰二氧化硅绝缘层界面。结果显示场迁移率得到极大提高,其最优特性高达0.91 cm2V-1s-1。     

Ag、Au纳米颗粒的激光表面修饰

通过用Nd：YAG激光（λ=1064nm）对氧化还原法制备的Ag、Au纳米颗粒的修饰,使Ag、Au纳米颗粒的尺寸均匀性得到更好的改善。用透射电子显微镜（TEM）和紫外-可见表面等离于体吸收（SPA）光谱对激光修饰后的Ag、Au纳米颗粒进行了测量和表征,结果表明,这些被修饰过的Ag、Au纳米颗粒由于自身体系发生了改变,可以作为更高效表面增强拉曼光谱（SERS）的增强基底。     

非晶In-Ga-Zn-O沟道薄膜晶体管存储器研究

非晶铟镓锌氧化物(a-IGZO)沟道薄膜晶体管存储器在先进系统面板领域具有重要的应用前景。首先阐明了a-IGZO材料在系统面板和柔性器件等应用中所具有的优势,然后对a-IGZO薄膜的制备方法及材料性能进行了归纳。最后对基于a-IGZO沟道薄膜晶体管存储器的结构、编程和擦除特性等文献报道进行了总结,重点讨论了该类存储器在通常情况下擦除效率低的原因及其改善措施。因此,对今后开发高性能a-IGZO沟道薄膜晶体管存储器具有很好的指导意义。     

绝缘层/有源层界面修饰及对有机薄膜晶体管性能的影响

制备了具有修饰层的有机薄膜场效应晶体管,采用高掺杂Si作为栅极,传统的无机绝缘材料SiO2作为栅绝缘层,有机绝缘材料PMMA或OTS作为修饰层,CuPc作为有源层,Au作为源、漏极.测试结果表明,采用经过修饰的栅绝缘层SiO2/OTS和SiO2/PMMA的两种器件的开关电流比最高可达8×104,迁移率最高为1.22×10-3cm2/(V·s),而漏电流仅为10-10A,总体性能优于单层SiO2器件.     

绝缘层/有源层界面修饰及对有机薄膜晶体管性能的影响

制备了具有修饰层的有机薄膜场效应晶体管,采用高掺杂Si作为栅极,传统的无机绝缘材料SiO2作为栅绝缘层,有机绝缘材料PMMA或OTS作为修饰层,CuPc作为有源层,Au作为源、漏极.测试结果表明,采用经过修饰的栅绝缘层SiO2/OTS和SiO2/PMMA的两种器件的开关电流比最高可达8×104,迁移率最高为1.22×10-3cm2/(V·s),而漏电流仅为10-10A,总体性能优于单层SiO2器件.     

Development and analysis of nitrogen-doped amorphous InGaZnO thin film transistors

The nitrogen-doped (N-doped) amorphous InGaZnO thin film transistors (a-IGZO TFTs) were investigated against the undoped and oxygen doped (O-doped) devices. The N-doped a-IGZO TFTs exhibited better electrical performance and bias stress stability, and especially more stable thermal properties. The X-ray photoemission spectroscopy (XPS) measurements were carried out at different temperatures (298 K and 393 K) to examine the physical essence of the thermal instability of undoped, O-doped, and N-doped a-IGZO TFTs. The XPS characterization results indicated that nitrogen doping caused lesser oxygen vacancy variation with the temperature (0.6%) compared with undoping (7.2%) and oxygen doping (11.8%). Hence, the a-IGZO TFTs with N-doped active layers had much better stability than those with undoped and O-doped active layers.     

IGZO thin film transistors with Al2O3 gate insulators fabricated at different temperatures

Thin film transistors (TFTs) with bottom gate and staggered electrodes using atomic layer deposited Al₂O₃ as gate insulator and radio frequency sputtered In–Ga–Zn Oxide (IGZO) as channel layer are fabricated in this work. The performances of IGZO TFTs with different deposition temperature of Al₂O₃ are investigated and compared. The experiment results show that the Al₂O₃ deposition temperature play an important role in the field effect mobility, I_on/I_off ratio, sub-threshold swing and bias stability of the devices. The TFT with a 250 °C Al₂O₃ gate insulator shows the best performance; specifically, field effect mobility of 6.3 cm²/Vs, threshold voltage of 5.1 V, I_on/I_off ratio of 4×10⁷, and sub-threshold swing of 0.56 V/dec. The 250 °C Al₂O₃ insulator based device also shows a substantially smaller threshold voltage shift of 1.5 V after a 10 V gate voltage is stressed for 1 h, while the value for the 200, 300 and 350 °C Al₂O₃ insulator based devices are 2.3, 2.6, and 1.64 V, respectively.     

Optimization of electrohydrodynamic-printed organic electrodes for bottom-contact organic thin film transistors

In this study, we investigate the optimization of printed (3,4-ethylenedioxythiophene):poly(4-styrenesulfonate) (PEDOT:PSS) as source/drain electrodes for organic thin film transistors (OTFTs) through electrohydrodynamic (EHD) printing process. The EHD-printed PEDOT:PSS electrodes should fulfill the prerequisites of not only high conductivity but also optimum surface tension for successful jetting. The conductivity of PEDOT:PSS was dramatically enhanced from 0.07 to 352 S/cm by the addition of dimethylsulfoxide (DMSO). To use the DMSO-treated PEDOT:PSS solution in the EHD printing process, its surface tension was optimized by the addition of surfactant (Triton X-100), which was found to enable various jetting modes. In the stable cone-jet mode, the patterning of the modified PEDOT:PSS solution was realized on the surface-functionalized SiO₂ substrates; the printed line widths were in the range 384 to 81 μm with a line resistance of 8.3 × 10³ Ω/mm. In addition, pentacene-based OTFTs employing the EHD-printed PEDOT:PSS as source and drain electrodes were found to exhibit electrical performances superior to an equivalent vacuum-deposited Au-based device.     

Device characteristics of amorphous indium gallium zinc oxide thin film transistors with ammonia incorporation

The effect of ammonia gas on amorphous indium gallium zinc oxide thin film transistors is investigated. The ammonia is incorporated into the sputtered a-IGZO film during the deposition process. The results indicate that the sub-threshold swing of the NH₃ incorporated TFTs is significantly improved from 2.8 to 1.0 V/decade, and the hysteresis phenomenon is also suppressed during the forward and reverse sweeping measurement. By X-ray photoelectron spectroscopy analyses, Zn-N and O-H bonds are observed in ammonia incorporated a-IGZO film. Therefore, the improvements in the electrical performance of TFTs are attributed to the passivation of dangling bonds and/or defects by ammonia.     

绝缘层材料及结构对薄膜晶体管性能的影响

基于半导体仿真软件Silvaco TCAD对薄膜晶体管(TFT)进行器件仿真,并结合实验验证,重点分析不同绝缘层材料及结构对TFT器件性能的影响。仿真及实验所用薄膜晶体管为底栅电极结构,沟道层采用非晶IGZO材料,绝缘层采用SiN_x和HfO_2多种不同组合的叠层结构。仿真及实验结果表明:含有高k材料的栅绝缘层叠层结构较单一SiN_x绝缘层结构的TFT性能更优;对SiN_x/HfO_2/SiN_x栅绝缘层叠层结构TFT,HfO_2取40nm较为合适;对含有高k材料的3层和5层绝缘层叠层结构TFT,各叠层厚度相同的对称结构TFT性能最优。本文通过仿真获得了TFT性能较优的器件结构参数,对实际制备TFT器件具有指导作用。     

A printing technology combining screen-printing with a wet-etching process for the gate electrodes of organic thin film transistors on a plastic substrate

We have developed a practical printing technology for the gate electrode of organic thin film transistors (OTFTs) by combining screen-printing with a wet-etching process using nano-silver (Ag) ink as a conducting material. An Ag film was deposited onto a PVP (polyvinylphenol)-coated PC (polycarbonate) plastic substrate by screen-printing with nano-Ag ink, where Ag content of 20 wt.% was mixed using a terpineol solvent. Subsequently, the film was cured at 200 °C for 60 min, and then finally wet-etched through patterned positive photo-resist masks. The screen-printed Ag electrode exhibited a minimum line width of ∼5 μm, a thickness of ∼65 nm, and a resistivity of ∼10⁻⁶ Ω cm, producing good geometrical and electrical characteristics for a gate electrode. Additionally, it also provided good step coverage with the PVP dielectric layer, and consequently leakage current between the gate and source/drain electrodes was eliminated. Moreover, the electrical characteristic of the screen-printed Ag electrode was not significantly changed even after a bending test in which the Ag electrodes were bent with a bending radius of 6 mm and 2500 iterations of cyclic bending. OTFTs with the screen-printed Ag electrode produced a saturation mobility of 0.13 cm²/Vs and a current on/off ratio of 1.79 × 10⁶, being comparable to those of an OTFT with a thermally evaporated Al gate electrode.     

Air-stable polythiophene-based thin film transistors processed using oxidative chemical vapor deposition: Carrier transport and channel/metallization contact interface

Oxidative chemical-vapor-deposition (oCVD) provides a facile route to polymerize and deposit insoluble monomers in thin film form. Here, we report on oCVD polythiophene (PT)-based organic thin film transistors (OTFTs) that present both high mobility and excellent stability over time in air. The measured field effect mobility (μ_FE) is ∼0.02 cm²/V sec with the low threshold voltage between −1 V and 0.3 V. Additionally the PT OTFTs show no evidence of performance degradation after 3 months exposure in air. The transmission line model (TLM) enables the determination of the specific contact resistance (ρ_C) of oCVD PT channel/metallization interface and reveals that ρ_C is improved with increasing gate bias. The oCVD PT channel conductivity (σ_ch) and carrier density (p) were evaluated from more than 100 devices using TLM measurements and the relation of σ_ch = qpμ_FE. Carrier transport analysis suggests that the charge screening effect governs hole carrier mobility in the carrier density regime below approximately 10¹⁸/cm³ where an increase in carrier density leads to higher mobility. We also demonstrate photo-conductivity of oCVD PT through an increase in device on-state current and the field effect mobility when the PT OTFT is illuminated. Strategies to further enhance the performance of the materials and devices are also suggested.     

Inkjet printed silver source/drain electrodes for low-cost polymer thin film transistors

Silver tracks for source/drain (S/D) electrodes in low-cost polymer thin film transistors (TFTs) have been realized through inkjet printing technique, using heavily n-doped silicon wafer with thermally grown silicon dioxide as the substrate and poly(3-hexylthiophene) (P3HT) as the channel material. Spin coating a layer of poly-4-vinylphenol (PVPh) onto the substrate was found to enhance the silver track uniformity and lower the cure temperature (from 300 to 210 °C). The surface roughness of the PVPh film was optimized to improve the device performance. The fabricated P3HT TFT with a channel length of 20 μm exhibited a saturation mobility of 3.5 × 10⁻2 cm²/V/s which was three times higher than that obtained in P3HT TFTs with gold S/D electrodes.     

Investigation of thermal effects on the single-finger heterojunction bipolar transistors

We will first derive a physics-based, analytical single-finger heterojunction bipolar transistor (HBT) model which takes into account the thermal effect. Next, the model is used to calculate the three figures of merit of HBT, i.e., current gain, cut-off frequency and maximum frequency. Their variation against the collector current density under the influence of thermal effect is presented and the calculation results are discussed.     

Numerical simulation of spin coated P3HT organic thin film transistors with field dependent mobility and distributed contact resistance

P3HT thin film transistors (TFT) have been fabricated using inkjet printing technique. The present work aims at the systematic study of the impact of distributed contact resistance including field dependent mobility. The coupled analysis is not yet explored for polymer organic thin film transistors. Numerical simulations are performed to study the coupled influence of field mobility and distributed contact resistance on the FET device behavior. Considering the influence of field mobility and distributed contact resistance, simulated results are consistent with our experimental results.