Low-temperature nickel-doped indium tin oxide anode for flexible organic light-emitting devices

Characteristics of an organic light-emitting diode (OLED) with a structure of Al/tris(8-hydroxyquinoline) aluminum (Alq3), N,N′-bis-(1-naphthyl)-N,N′-diphenyl-1, 1′biphenyl-4, 4′-diamine(NPB)/indium tin oxide (ITO)/Arton film have been improved by the introduction of Ni atoms in the ITO surface layer. The threshold voltage and turn-on voltage of an OLED device with Ni sputter power of 90 W and ITO surface oxygen plasma treatment can be reduced, respectively, by 3.4 V and 2.6 V. The existence of Ni atoms and the formation of Ni oxide phases on ITO surface are suggested for the improved characteristics.     

Organic field-effect transistor with extended indium tin oxide gate structure for selective pH sensing

In this study, organic field-effect transistors (OFETs) with extended gate structure were fabricated for selective pH sensing applications. Indium tin oxide (ITO) was used as extended gate electrode as well as an active layer for H⁺ sensing. The threshold voltage of the fabricated ion-selective OFET was varied by the changes in the electrochemical potential at the ITO electrode surface upon its exposure to buffer solutions with variable pH values. The sensor showed excellent linearity and a high sensitivity of 57–59 mV/pH in the pH range of 2–12. The selectivity of the ITO sensing layer to H⁺ ions was also investigated by measuring the interfering effect of Ca²⁺ and K⁺ ions in the buffer pH solutions. The results showed that the Ca²⁺ and K⁺ ions weakly interfere with the selective pH sensing of the ITO-extended gate OFET sensor device.     

Work function changes of plasma treated indium tin oxide

The work function (WF) changes of indium tin oxide (ITO) treated by O₂ or Cl₂ plasma were invested. The WF firstly decreases in an exponential way for 2–6 h and subsequently in a linear way for days in air after plasma treatment. X-ray photoelectron spectroscopy (XPS) shows the dipole layer formed by O–In and O–O bonds in the ITO surface treated by O₂ plasma increases the WF. Exposed in vacuum, the O–O bonds tend to break and the reactive O species reduce in the oxidized ITO surface, accounting for the exponential decrease of WF. The environment preserving the chlorinated or oxidized ITO is important to slow down the decrease of WF. The mechanism for WF changes of plasma treated ITO is significant to investigate the properties of organic optoelectronic devices.     

Optical and electrical effects of nickel oxide interlayer for anode-recessed organic light-emitting diodes

Forming a nickel oxide (NiO_x) layer on recessed indium tin oxide (ITO) anodes has successfully enhanced the current efficiency of an organic light emitting diode (OLED) by up to 46%. The recesses largely increased the haze of ITO film and led to a 32.8% current efficiency enhancement of a planar OLED. The introduced NiO_x interlayer allowed another 12.9% efficiency enhancement mainly due to lowered potential barrier at the ITO/organic interface and further elevated haze that led to a more efficient light extraction.     

Organic light-emitting diodes fabricated on recessed anodes for light extraction enhancement

Circular recesses have been fabricated on indium tin oxide (ITO) anodes to enhance light extraction of organic light-emitting diodes (OLEDs). The effects of recess depth and recess coverage ratio on the performance of a green OLED were systematically investigated. Results showed that the current efficiency could be enhanced from 40.7 cd/A of a planar device to 47.2 cd/A of the device with a recess depth of 100 nm and a recess coverage ratio of 14.1%. The enhanced light extraction by the recess wall effect was realized to be the major factor leading to the improved efficiency. The efficiency is however limited by the accompanying increase in electrical resistivity of the ITO films at deep recesses and high recess coverage ratios. Despite of the insignificant efficiency enhancement (up to 16%) in this study, this recessed ITO approach provides a simple architecture to enhance waveguide mode light extraction without adding an internal medium.     

Influence of H<Subscript>2</Subscript>- and N<Subscript>2</Subscript>-ambient annealing of indium-tin oxide film on plastic substrate for organic light-emitting diode

Indium tin oxide (ITO) film was deposited on an ARTON plastic substrate using 80 W, direct current (DC) magnetron sputtering on an unheated substrate, then annealed at 150°C under either hydrogen or nitrogen gas for periods ranging from 2 h to 8 h. Film surface morphology, crystal size, crystal orientation, and visible region optical transparency were studied. The grain size was found to increase with increased annealing time. Grain size was larger under nitrogen ambience than under hydrogen ambience. Sheet resistance of as-deposited ITO films was 87Ω/sq, but with nitrogen ambient annealing at 150°C for 8 h, it declined to 65Ω/sq. Average ITO-film transmittance was 88% after an 8-h nitrogen-ambient annealing.     

Evaluation of electrical and optical properties of indium tin oxide thin film using chemical mechanical polishing technique

In this study, the optimum process parameters and the influences of their process parameters were investigated for indium tin oxide-chemical mechanical polishing (ITO-CMP) with the sufficient removal rate and the good planarity. And then, the optical property such as transmittance and absorption efficiency, and the electrical characteristics such as sheet resistance, carrier density and Hall mobility were discussed in order to evaluate the possibility of CMP application for the organic light emitting display (OLED) device using an ITO film. Light transmission efficiency and current-voltage characteristics of ITO thin film were improved after CMP process using optimized process parameters compared to that of as-deposited thin film before CMP process.     

Comparison of dimethyl sulfoxide treated highly conductive poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) electrodes for use in indium tin oxide-free organic electronic photovoltaic devices

Indium tin oxide (ITO)-free organic photovoltaic (OPV) devices were fabricated using highly conductive poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) as the transparent conductive electrode (TCE). The intrinsic conductivity of the PEDOT:PSS films was improved by two different dimethyl sulfoxide (DMSO) treatments – (i) DMSO was added directly to the PEDOT:PSS solution (PEDOT:PSS_ADD) and (ii) a pre-formed PEDOT:PSS film was immersed in DMSO (PEDOT:PSS_IMM). X-ray photoelectron spectroscopy (XPS) and conductive atomic force microscopy (CAFM) studies showed a large amount of PSS was removed from the PEDOT:PSS_IMM electrode surface. OPV devices based on a poly(3-hexylthiophene):[6,6]-phenyl-C₆₁-butyric acid methyl ester (P3HT:PCBM) bulk hetrojunction showed that the PEDOT:PSS_IMM electrode out-performed the PEDOT:PSS_ADD electrode, primarily due to an increase in short circuit current density from 6.62 mA cm⁻² to 7.15 mA cm⁻². The results highlight the importance of optimising the treatment of PEDOT:PSS electrodes and demonstrate their potential as an alternative TCE for rapid processing and low-cost OPV and other organic electronic devices.     

Photo-degradation of the indium tin oxide (ITO)/organic interface in organic optoelectronic devices and a new outlook on the role of ITO surface treatments and interfacial layers in improving device stability

This work focuses on the effect of light exposure on ITO/organic interface in organic optoelectronic devices, including organic light emitting devices (OLEDs), organic photo-detectors (OPDs) and organic solar cells (OSCs). The results show that irradiation by light in the visible and UV range leads to a gradual deterioration in charge injection and extraction across the interface. A correlation between the performance stability of the devices and the photo-stability of the ITO/organic contacts is established. Studies also show that this photo-induced degradation can be significantly reduced by means of ITO surface treatment or through the insertion of interfacial layers between ITO and the organic layers. X-ray Photoelectron Spectroscopy (XPS) measurements reveal detectable changes in the interface characteristics after irradiation, indicating that the photo-degradation of the ITO/organic contacts is chemical in nature. Changes in XPS characteristics after irradiation suggest a possible reduction in bonds between ITO and its adjacent organic layer. The results shed light on a new material degradation mechanism that appears to have a wide presence in ITO/organic contacts in general, and which may play a key role in limiting the stability of various organic optoelectronic devices such as OLEDs, OSCs and OPDs.     

Low-cost supercritical CO2/H2O2 treatment on ITO anodes of fluorescent organic light-emitting diodes

A simple and cost-effective approach is proposed as an alternative to conventional oxygen plasma treatment to modify surface property of Indium tin oxide (ITO) anode of a fluorescent organic light-emitting diode (OLED). This was achieved by treating the ITO anode in supercritical CO₂ (SCCO₂) fluids with hydrogen peroxide (H₂O₂). The SCCO₂/H₂O₂ treatment yielded an ITO work function of 5.35 eV after 15 min treatment at 85 °C and 4000 psi, which was significant higher than 4.8 eV of the as-cleaned ITO surface and was slightly less than 5.5 eV of the ITO surface treated by oxygen plasma. The highest work function achieved was 5.55 eV after 45 min SCCO₂/H₂O₂ treatment. The SCCO₂/H₂O₂ treatment can be used to tailor the ITO work function through changing the operation pressure of the treatment. In addition, the correlated dependence of OLED performance on the ITO anodes with and without the treatments was investigated. The maximum power efficiency of 1.94 lm/W was obtained at 17.3 mA/cm² for the device with 15 min SCCO₂/H₂O₂ treatment at 4000 psi. This power efficiency was 19.3% and 33.8% higher than those of the oxygen plasma treatment and as-clean, respectively. The improvement in device efficiency by the SCCO₂/H₂O₂ treatments can be attributed to enhanced hole injection and balance in charge carriers due to increased work function and surface energy of the ITO anodes.     

Influence of thermal annealing on electrical and optical properties of indium tin oxide thin films

Transparent conducting indium tin oxide (ITO) thin films with the thickness of 300 nm were deposited on quartz substrates via electron beam evaporation, and five of them post-annealed in air atmosphere for 10 min at five selected temperature points from 200 °C to 600 °C, respectively. An UV–vis spectrophotometer and Hall measurement system were adopted to characterize the ITO thin films. Influence of thermal annealing in air atmosphere on electrical and optical properties was investigated in detail. The sheet resistance reached the minimum of 6.67 Ω/sq after annealed at 300 °C. It increased dramatically at even higher annealing temperature. The mean transmittance over the range from 400 nm to 800 nm reached the maximum of 89.03% after annealed at 400 °C, and the figure of merit reached the maximum of 17.79 (Unit: 10⁻³ Ω⁻¹) under the same annealing condition. With the annealing temperature increased from 400 °C to 600 °C, the variations of transmittance were negligible, but the figure of merit decreased significantly due to the deterioration of electrical conductivity. With increasing the annealing temperature, the absorption edge shifted towards longer wavelength. It could be explained on the basis of Burstein–Moss shift. The values of optical band gap varied in the range of 3.866–4.392 eV.     

Deposition and characterization of indium oxide and indium tin oxide semiconducting thin films by reactive thermal deposition technique

In this paper, the deposition conditions and the characterization properties of the indium oxide (10) and indium tin oxide (ITO) thin films deposited by a reactive thermal deposition technique using the indium, indium-tin alloy sources are reported. The actively involved parameters during deposition have been identified for various substrate temperatures. The effect of oxygen partial pressure in evaporation has been identified. The indium-tin alloy source which was used in this work was prepared by hot zone diffusion technique. The structural, optical, and electrical properties have been characterized using optical microscope, x-ray diffractometer, ultraviolet spectrophotometer, and Hall effect measurement setup. The uniformity of the deposited films and the uniformity of the substrate surface effect on the deposited thin films were analyzed through sheet resistance measurements. The depositions were carried out on glass and quartz substrates. Good optical transmittance (99%) was achieved for 740 nm wavelength and above. The absorbance spectrum exhibit a value of 2% absorbance for IO/quartz structures. Large area (5.0 × 3.8 cm) film with unique optical properties is also reported here.     

射频磁控溅射ITO薄膜中沉积温度对膜特性影响

采用射频磁控溅射的方法,在溅射过程中改变沉积温度以提高铟锡氧化物(ITO)薄膜的电学和光学特性。采用扫描电镜(SEM)分析了ITO薄膜的表面形貌,发现ITO薄膜的晶粒尺寸随着衬底温度的升高而增大。经过后续退火,ITO薄膜的电学特性得到了较大的提高。在溅射条件为工作气压1 Pa、衬底温度200℃和输入功率200 W沉积的样品经过300℃真空退火2 h获得了12.8×10-4Ω.cm的低电阻率和800 nm波段94%的高透过率。     

Effect of substrate temperature on indium tin oxide (ITO) thin films deposited by jet nebulizer spray pyrolysis and solar cell application

This study focused on the effect of substrate temperature (350 °C, 400 °C, and 450 °C) on morphological, optical, and electrical properties of indium tin oxide (ITO) films deposited onto porous silicon/sodalime glass substrates through jet nebulizer spray pyrolysis for use in heterojunction solar cells. X-ray diffraction analysis confirmed the formation of pure and single-phase In₂O₃ for all the deposited films whose crystallinity was enhanced with increasing substrate temperature, as shown by the increasing (222) peak intensity. Morphological observations were conducted using scanning electron microscopy to reveal the formation of continuous dense films composed of nanograins. The UV–vis spectra revealed that the transmittance increased with increasing substrate temperature, reaching a value of over 80% at 450 °C. The photoelectric performance of the solar cell was studied using the I–V curve by illuminating the cell at 100 mW/cm². A high efficiency (η) of 3.325% with I_sc and V_oc values of 14.8 mA/cm² and 0.60 V, respectively, was attained by the ITO solar cell annealed at 450 °C.     

Indium Tin Oxide Thin Films Grown on Polyethersulphone (PES) Substrates by Pulsed‐Laser Deposition for Use in Organic Light‐Emitting Diodes

High quality indium tin oxide (ITO) thin films were grown by pulse laser deposition (PLD) on flexible polyethersulphone (PES) substrates. The electrical, optical, and surface morphological properties of these films were examined as a function of substrate temperature and oxygen pressure. ITO thin films, deposited by PLD on a PES substrate at room temperature and an oxygen pressure of 15 mTorr, have a low electrical resistivity of 2.9×10^?4 Ω cm and a high optical transmittance of 84 % in the visible range. They were used as the anode in organic light‐emitting diodes (OLEDs). The maximum electro luminescence (EL) and current density at 100 cd/m² were 2500 cd/m² and 2 mA/cm², respectively, and the external quantum efficiency of the OLEDs was found to be 2.0 %.     

低温ITO薄膜制备及其在TOLED中的应用

通过在直流磁控溅射过程中加入微量水蒸气的方法,在低于60℃温度条件下制备了具有优良光电性能的透明导电ITO薄膜,并探讨了溅射功率、基板温度对ITO薄膜光电性能的影响.利用制得的ITO薄膜作电极,制作了结构为ITO/CuPc/NPB/Alq3/BCP/Mg:Ag/ITO的透明有机电致发光器件(TOLEDs),结果表明,器件的平均透过率达到45%;在驱动电压15 V的条件下,发光亮度达到了3000 cd/m2.     

Organic light-emitting devices with a 2-(4-biphenyl)-5-(4-butylphenyl)-1,3,4-oxadiazole layer between the α-naphtylphenyliphenyl diamine and 8-hydroxyquinoline aluminum

Organic light-emitting devices (OLEDs) with a 2-(4-biphenyl)-5-(4-butylphenyl)-1,3,4-oxadiazole layer between the α-naphtylphenyliphenyl diamine and 8-hydroxyquinoline aluminum were fabricated using a vacuum evaporation method. Compared to the different thickness of the buffer layer, the OLEDs with the 1.0 nm buffer layer showed the maximum power efficiency. The enhancements in power efficiency result from an improved balance of hole and electron injections. After comparing among different density buffer layer, PBD are good candidates for hole-injecting buffer layer, and 1.0 nm PBD buffer layer shows better operational durability and life.     

ITO薄膜制备及RTA处理对发光器件特性的影响

采用射频反应磁控溅射生长铟锡氧化物(ITO)薄膜,通过X射线衍射(XRD)、透射光谱、四探针法及原子力显微镜(AFM)研究了生长条件、快速热退火(RTA)温度等对薄膜的晶化、透过率、电导率以及表面形貌的影响.以ITO/NPB/AlQ/Al结构的器件为例,讨论了不同的制备条件下ITO薄膜的表面效应对电致发光(EL)的影响,通过EL光谱表征发现,对ITO退火处理后,器件的相对发光强度明显增加,衰减速度减慢,器件的EL光谱有明显的变化.通过进一步分析认为,这是由于ITO薄膜表面的变化引起功函数的改变,从而引起电场重新分布造成的.     

PLD法制备ITO导电薄膜及其性能

为了研制可用于高温环境下进行应变测量的应变层,采用脉冲激光沉积(PLD)法在陶瓷基底上制备了氧化铟锡(ITO)薄膜.研究了PLD法中不同基底温度对ITO薄膜显微结构、电学性能以及阻温特性的影响.采用X射线衍射仪(XRD)测试了薄膜的晶体结构,通过四点探针测量法测得薄膜的薄层电阻,采用场发射扫描电子显微镜(FESEM)对...     

低温生长ITO薄膜及其在太阳电池中的应用

氧化铟锡(ITO)同时结合了可见光范围内高透过率和高电导率等特性,被广泛应用于Si基薄膜太阳电池中。本文侧重研究了采用反应热蒸发(RTE)技术低温(约160℃)生长ITO透明导电薄膜过程中不同Sn掺杂含量对薄膜微观结构以及光电性能的影响。实验结果表明,随着Sn掺杂含量的增加,ITO薄膜微观结构稍有变化,薄膜的电子迁移率呈现先增大后减小的趋势,薄膜的光学带隙一定程度上呈现展宽趋势;对于较高的Sn掺杂含量,在低温条件下电离杂质散射和中性杂质散射成为影响电子迁移率降低的重要因素。经过薄膜生长优化,较佳的Sn掺杂含量为6.0wt.%,ITO薄膜电阻率为3.74×10-4Ω·cm,电子迁移率为47cm2/Vs,载流子浓度为3.71×1020cm-3,且在380~900nm波长范围内的平均透过率约87%。将其应用于结构为SS/Ag/ZnO/nip aSiGe:H/nipa-Si:H/ITO/Al的n-i-p型a-Si:H/a-SiGe:H叠层太阳电池,取得的光电转化效率达10.51%(开路电压Voc=1.66V,短路电流密度Jsc=9.31mA/cm2,填充因子FF=0.68)。