Enhanced performance in organic photovoltaic devices with KMnO4 solution treated indium tin oxide anode modification

The properties of poly(3-hexylthiophene):(6,6)-phenyl C₆₁ butyric acid methyl ester (P3HT:PCBM) organic photovoltaic devices (OPVs) with indium tin oxide (ITO) anode treated by KMnO₄ solution are investigated. The optimized KMnO₄ solution has a concentration of 50 mg/L, and ITO is treated for 15 min. The modification of ITO anode results in an enhancement of the power conversion efficiency (PCE) of the device, which is responsible for the increase of the photocurrent. The performance enhancement is attributed to the work function modification of the ITO substrate through the strong oxygenation of KMnO₄, and then the charge collection efficiency is improved.     

The enhanced performance of organic light-emitting diodes by using PCBM as the anode modification layer

[6,6]-Phenyl C₆₁ butyric acid methyl ester (PCBM) is used to modify an indium tin oxide (ITO)-coated substrate. Organic light-emitting diodes (OLEDs) using PCBM as the anode modification layer are fabricated. The dependence of performance on different PCBM thicknesses is also investigated. When the thickness of the PCBM film is appropriate, the brightness and efficiency of OLEDs are enhanced, which is attributed to an enhanced hole injection and an improved carrier balance. The enhancement of hole injection was ascribed to the formation of a dipole layer at the anode/organic interface.     

Contribution of O2 plasma treatment and amine modified GOs on film properties of conductive PEDOT:PSS: Application in indium tin oxide free solution processed blue OLED

Primary (n-propyl amine, n-PRYLA), secondary (dipropyl amine, DPRYLA) and alcohol (propanol amine, PRPOHA) amine derivatives were used as amine sources in graphene oxide (GO) modification and obtained samples were named as nPRYLA-GO, DPRYLA-GO and PRPOHA-GO, respectively. Modified graphene oxide (mGO) derivatives were doped in poly (3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PH1000) and O₂ plasma treatment (70W, 3 min) was applied on the spin casted films. PH1000:mGO films presented high optical transparency values (>90%) and low resistivity (177–183 Ω/sq). The roughness values were increased especially when the hydrophobic alkyl chain containing DPRYLA-GO and nPRYLA-GO were doped in PH1000. Prepared films were utilized as anode in solution processed blue organic light emitting diode. PH1000:PRPOHA-GO anode presented more than 30 nm of decrement in full with at half maximum and 1.6, 1.5 and 1.9 fold enhancements in current, power and external quantum efficiency values, compared to those of ITO anode, respectively.     

Improved performance of organic light-emitting devices with plasma treated ITO surface and plasma polymerized methyl methacrylate buffer layer

Transparent indium-tin-oxide (ITO) anode surface was modified using O₃ plasma and organic ultra-thin buffer layers were deposited on the ITO surface using 13.56 MHz rf plasma polymerization technique. A plasma polymerized methyl methacrylate (ppMMA) ultra-thin buffer layer was deposited between the ITO anode and hole transporting layer (HTL). The plasma polymerization of the buffer layer was carried out at a homemade capacitively coupled plasma (CCP) equipment. N,N′-Diphenyl-N,N′-bis(3-methylphenyl)-1,1′-diphenyl-4,4′-diamine (TPD) as HTL, Tris(8-hydroxy-quinolinato)aluminum (Alq₃) as both emitting layer (EML)/electron transporting layer (ETL), and aluminum layer as cathode were deposited using thermal evaporation technique. Electroluminescence (EL) efficiency, operating voltage and stability of the organic light-emitting devices (OLEDs) were investigated in order to study the effect of the plasma surface treatment of the ITO anode and role of plasma polymerized methyl methacrylate as an organic ultra-thin buffer layer.     

Improvement of organic solar cells by flexible substrate and ITO surface treatments

In this paper, surface treatments on polyethylene terephthalate with polymeric hard coating (PET-HC) substrates are described. The effect of the contact angle on the treatment is first investigated. It has been observed that detergent is quite effective in removing organic contamination on the flexible PET-HC substrates. Next, using a DC-reactive magnetron sputter, indium tin oxide (ITO) thin films of 90 nm are grown on a substrate treated by detergent. Then, various ITO surface treatments are made for improving the performance of the finally developed organic solar cells with structure Al/P3HT:PCBM/PEDOT:PSS/ITO/PET. It is found that the parameters of the ITO including resistivity, carrier concentration, transmittance, surface morphology, and work function depended on the surface treatments and significantly influence the solar cell performance. With the optimal conditions for detergent treatment on flexible PET substrates, the ITO film with a resistivity of 5.6 × 10⁻⁴ Ω cm and average optical transmittance of 84.1% in the visible region are obtained. The optimal ITO surface treated by detergent for 5 min and then by UV ozone for 20 min exhibits the best WF value of 5.22 eV. This improves about 8.30% in the WF compared with that of the untreated ITO film. In the case of optimal treatment with the organic photovoltaic device, meanwhile, 36.6% enhancement in short circuit current density (J_sc) and 92.7% enhancement in conversion efficiency (η) over the untreated solar cell are obtained.     

PECVD制备AZO（ZnO:Al）透明导电薄膜

采用PECVD（等离子体增强化学气相沉积）工艺在普通玻璃和Si基上制备出了方块电阻低至89 Ω,可见光透过率高达79%,对基体附着力强的多晶态的AZO（ZnO:Al）薄膜.采用PECVD法制备AZO薄膜是一种有益的尝试,AZO透明导电薄膜不仅具有与ITO（透明导电薄膜,如In₂O₃:Sn）可比拟的光电特性,而且价格低廉、无毒,在氢等离子体环境中更稳定,所获结果对实际工艺条件的选择具有一定借鉴作用和参考价值. 关键词： AZO（ZnO:Al） 等离子体增强化学气相沉积 透明导电薄膜     

Durability enhancement and degradation of oxygen evolution anodes in seawater electrolysis for hydrogen production

For the anode composed of electrocatalyst oxide, intermediate layer and titanium substrate, the substitution of a certain amount of iridium with tin in the IrO₂ intermediate layer was remarkably effective in elongating the life of the anode in preventing oxidation of the substrate titanium during oxygen evolution. The longest life was realized by preparation of intermediate layer with uniform thickness by brush-coating of H₂IrCl₆-SnCl₄ butanol solution and subsequent calcination. The anode with the intermediate layer prepared from 0.04 M H₂IrCl₆-0.06 M SnCl₄ butanol solution showed the best performance, that is, the oxygen evolution efficiency higher than 99.8% for more than 4300 h in the electrolysis of 0.5 M NaCl solution of pH 1 at the current density of 1000 Am⁻². An increase in SnCl₄ concentration decreased the viscosity of the coating solution with a consequent enhancement of uniformity of the intermediate layer but decreased the thickness of the intermediate layer acting as a barrier to prevent oxidation of titanium. Thus, the best performance was attained at an intermediate SnCl₄ concentration. The growth of an oxide layer on titanium during electrolysis occurred and was found by the potential increase.     

使用PTB7作为阳极修饰层提高有机发光二极管的性能

采用poly[[4,8-bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5-b’]dithiophene-2,6-diyl][3-?uoro-2-[(2-ethylhexyl)carbonyl]thieno[3,4-b]thiophenediyl]](PTB7)作为有机发光二极管器件的阳极修饰层,制备了结构为indium tin oxide(ITO)/PTB7(不同浓度)/N,N’-Bis(naphthalen-1-yl)-N,N’-bis(phenyl)benzidine(NPB,40 nm)/8-hydroxyquinoline(Alq3,60 nm)/LiF(1 nm)/Al的系列器件,同时研究了不同浓度的PTB7对器件性能的影响.PTB7的最佳浓度为0.25 mg/mL,器件性能得到明显的改善,起亮电压为4.3 V.当驱动电压为14.6 V时,最大亮度为45800 cd/m2,最大电流效率为9.1 cd/A.与没有PTB7修饰的器件相比,其起亮电压降低了1.9 V,最高亮度提升了78.5%.器件性能提高归因于PTB7的插入使得空穴注入和传输能力大大改善.     

Surface modification of indium tin oxide anode with self-assembled monolayer modified Ag film for improved OLED device characteristics

Modification of electrodes has attracted much attention in the study of organic semiconductor devices. A self-assembled monolayer (SAM) of 4-fluorothiophenol is employed to modify the Ag film on the surface of indium tin oxide (ITO) to improve the hole injection and the surface morphology. The modified anode was characterized by X-ray photoelectron spectroscopy (XPS), atomic force microscope (AFM), and UV–vis transmittance spectra. To investigate the effect of the modification on the device characteristics, typical double layer devices with the structure of anode/-naphthylphenylbiphenyl diamine (NPB, 60 nm)/tris-(8-hydroxyquinoline) aluminum (Alq₃, 60 nm)/LiF(0.7 nm)/Al(100 nm) were fabricated using the modified anode and the bare ITO. The effect of Ag layer thickness on the device performance is also investigated. The results revealed that SAM modified ultra-thin Ag film is an effective buffer layer for organic light emitting diode. The device using the ITO/Ag (5 nm)/SAM as anode show improved device characteristics than that of using bare ITO as anode. The enhancements in luminance and efficiency are attributed to enhanced hole injection and smooth surface between anode and the organic material. The Ag thickness of 5 nm is chosen as an acceptable compromise between substrate transparency and the device performance.     

Highly transparent Ag doped In2O3 electrodes with high work function for organic solar cells

We report highly transparent Ag-doped In₂O₃ (IAO) films with high work function for use as transparent anodes in organic solar cells (OSCs). The electrical, optical, structural, and morphological properties of IAO films and their work function were investigated as a function of the rapid thermal annealing (RTA) temperature. At an RTA temperature of 600 °C, the IAO film showed a sheet resistance of 23.12 Ohm/square, an optical transmittance of 79.28%, and a work function of 5.21 eV, similar to conventional Sn-doped In₂O₃ (ITO) films. The low resistivity of the IAO film was closely related to oxygen vacancies caused by Ag suboxide formation in the In₂O₃ matrix. A bulk-heterojunction OSC with the optimized IAO anode showed performance comparable to that of an OSC with a reference ITO anode, indicating that the IAO films is a promising anode material for use in OSCs.     

有机薄膜电致发光器件载流子注入和传输性质的研究

制备了不同电极、不同厚度、以8-羟基喹啉铝螯合物(Alq3)为发光层的有机薄膜电致发光(TFEL)器件。分析了它们的电流密度-电压关系。不同阳极器件的电流变化很大,而改变阴极时电流密度的变化较小,说明电流以空穴为主。根据不同阴极器件的电致发光效率的比较,说明电子是决定器件电致发光效率的少数载流子。从不同厚度的器件的结果讨论了载流子的传输性质,认为在ITO/Alq3/Al器件中的电流符合陷阱限制的空间电荷电流.     

Optical Flow-Through Sensor for the Determination of Norfloxacin Based on Emission of KMnO<Subscript>4</Subscript>–Na<Subscript>2</Subscript>SO<Subscript>3</Subscript>–Tb<Superscript>3+</Superscript> System

A simple and selective method to determine norfloxacin using an optical flow-through sensor has been developed. The present sensor was prepared by packing anionic ion exchange resin in a glass tube, followed by introducing KMnO₄ solution to the glass tube for immobilization on resin. The optical sensor is based on the emission intensity from the Tb(III) solution sensitized by norfloxacin. The excitation of norfloxacin occurred by the chemiluminescence from the reaction of KMnO₄ and Na₂SO₄ solutions. The effects of pH, concentration of Tb(III) ion, KMnO₄ and Na₂SO₄ solutions and flow rate of the norfloxacin solution on the chemiluminescence intensity were studied to find the optimum experimental conditions. The emission intensity increased linearly with increasing norfloxacin concentration from 1.0 × 10⁻³ to 1.0 × 10⁻⁸ M and the detection limit (3σ) was 8.7 × 10⁻⁹. The applicability of the present method was demonstrated by determination of norfloxacin in various pharmaceutical preparations and serum sample.     

Highly stable inverted poly (3-hexylthiophene):methano-fullerene [6,6]-phenyl C71-butyric acid methyl ester bulk heterojunction solar cell with thin oxide nano particle layer using solution process

We have investigated the inverted poly (3-hexylthiophene):methano-fullerene [6,6]-phenyl C71-butyric acid methyl ester (P3HT:PC₇₁BM) bulk heterojunction (IBHJ) solar cell with various n-type metal oxide nano particle layers on ITO and MoO₃ anode buffer layer underneath Al. The IBHJ solar cell with a tin oxide nano particle layer shows the power conversion efficiency (PCE) of 3.1% and better stability compared to conventional BHJ solar cell. The PCE of this cell decreases by 3% after 2 months in ambient air while the other cells show more degradation.     

The visible and ultraviolet organic light-emitting diodes with germanium dioxide as facile solution-processed anode buffer layer

Germanium dioxide (GeO₂) aqueous solutions are facilely prepared and the corresponding anode buffer layers (ABLs) with solution process are demonstrated. Atomic force microscopy, X-ray photoelectron spectroscopy and ultraviolet photoelectron spectroscopy measurements show that solution-processed GeO₂ behaves superior film morphology and enhanced work function. Using GeO₂ as ABL of organic light-emitting diodes (OLEDs), the visible device with tris(8-hydroxy-quinolinato)aluminium as emitter gives maximum luminous efficiency of 6.5 cd/A and power efficiency of 3.5 lm/W, the ultraviolet device with 3-(4-biphenyl)-4-phenyl-5-tert-butylphenyl-1,2,4-triazole as emitter exhibits short-wavelength emission with peak of 376 nm, full-width at half-maximum of 42 nm, maximum radiance of 3.36 mW/cm² and external quantum efficiency of 1.5%. The performances are almost comparable to the counterparts with poly (3,4-ethylenedioxythiophene):poly (styrenesulfonate) as ABL. The current, impedance, phase and capacitance as a function of voltage characteristics elucidate that the GeO₂ ABL formed from appropriate concentration of GeO₂ aqueous solution favors hole injection enhancement and accordingly promoting device performance.     

Indium tin oxide surface treatments for improvement of organic light-emitting diode performance

We have systematically investigated the influence of UV ozone and acid (HCl) treatments (separate and combined) of the surface of indium tin oxide (ITO) on the ITO parameters and the performance of organic light-emitting diodes (OLEDs) fabricated on the treated substrates. The ITO substrates were characterized by Hall measurements, Seebeck coefficient measurements and surface-probe microscopy. After ITO characterization, two types of devices (ITO/NPB/rubrene/Alq₃/LiF/Al and ITO/TPD/rubrene/Alq₃/LiF/Al) were fabricated on the differently treated substrates. It was found that in both cases the optimal treatment was HCl followed by UV ozone, which resulted in the lowest turn-on voltage and the highest luminous efficiency. The maximum luminous efficiency in the ITO/NPB/rubrene/Alq₃/LiF/Al OLED with HCl followed by UV ozone treatment was 2.15 lm/W compared to 1.46 lm/W with UV ozone treatment only. PACS 81.65Cf; 85.60.Jb     

Oxidation of Activated Carbon in Liquid Phase. Study by FT-IR

Surface chemistry of a commercial activated carbon (AC) and of products oxidized in liquid phase using aqueous solutions of a series of oxidizing agents (H₂SO₄, HNO₃, HClO₄, H₂O₂, O₃, ClO₂, KlO₄ and KMnO₄) has been studied by FT-IR. Oxidation led to surface groups and structures which, and also the extend of formation, depended on the oxidizing agent and the pH and concentration of the solution used. Most oxidizing agents proved to be effective for the formation of surface C[dbnd]O groups. Variations in pH of solutions of H₂O₂, KlO₄ and KMnO₄ unequally affected the oxidation of AC. This was unfavourable with the increase in concentration of the solutions of HNO₃ and KMnO₄. The reverse was noted with KlO₄.     

Improving hole injection ability using a newly proposed WO3/NiOx bilayer in solution processed quantum dot light-emitting diodes

We propose a novel device structure with a WO₃/NiO_x bilayer to improve the hole injection ability in QLEDs fabricated mainly by a solution-based process. First, we employed a spin-coated NiO_x thin film as a hole injection layer (HIL) to replace Poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate) PEDOT:PSS which corrodes indium tin oxide (ITO) used as an anode in QLEDs. We showed a simply optimized annealing process, instead of a rather complicated process like doping, can improve the electrical conductivity of the NiO_x thin film. The reason for the dependency of conductivity on the post-metallization annealing is because of the change of the total amount of Ni vacancy in the NiO_x thin film as a function of annealing temperature: The electrical conductivity of the NiO_x thin film annealed at 275 °C was the best in this work. Second, we inserted the WO₃ thin film in between ITO electrode and NiO_x HIL to form an ITO/WO₃/NiO_x structure which reduces the hole injection barrier to 0.35 eV, resulting in the excellent characteristic in view of charge balance. Finally, we measured the properties of QLEDs with the WO₃/NiO_x bilayer to check the effects of the proposed device structure and showed the substantial improvement of the electrical conductivity of NiO_x, the luminance, and the current efficiency of the QLEDs.     

Polymer-based multi-layer conductive electrode film for plastic LCD applications

Thin films of polymer-based multi-layer conductive electrode to be used as a substrate for a plastic liquid crystal display (LCD) have been prepared by a DC magnetron roll-to-roll sputtering method. The conductive layer is composed of three layers, ITO/Ag/ITO or ITO/APC/ITO, where APC is Ag-Pd-Cu alloy, on the polymer substrate (Arton?), which has been treated with hard-coat and gas-barrier layers. The properties of the conductive electrode for the plastic LCD were the following: (1) sheet resistance is 6 Ω/square; (2) transparency is 88% at 550 nm; (3) H₂O gas permeation through the plastics is 0.35 g/m² in 24 h; (4) durability against solvents is good for 5% NaOH solution, IPA, methanol, NMP, acetone, etc.; (5) the irreversible shrinkage and the compaction rate are both less than 3 ppm/h after annealing for 100 h at 150 °C. Received: 22 January 2001 / Accepted: 30 January 2001 / Published online: 26 April 2001     

Effect on the reduction of the barrier height in rear-emitter silicon heterojunction solar cells using Ar plasma-treated ITO film

In this study, we investigated the effect of plasma treatment on an indium tin oxide (ITO) film under an ambient Ar atmosphere. The sheet resistance of the plasma-treated ITO film at 250 W (37.6 Ω/sq) was higher than that of the as-deposited ITO film (34 Ω/sq). Plasma treatment was found to decrease the ITO grain size to 21.81 nm, in comparison with the as-deposited ITO (25.49 nm), which resulted in a decrease in the Hall mobility. The work function of the Ar-plasma-treated ITO (WF_ITO=4.17 eV) was lower than that of the as-deposited ITO film (WF_ITO = 5.13 eV). This lower work function was attributed to vacancies that formed in the indium and oxygen vacancies in the bonding structure. Rear-emitter silicon heterojunction (SHJ) solar cells fabricated using the plasma-treated ITO film exhibited an open circuit voltage (V_OC) of 734 mV, compared to SHJ cells fabricated using the as-deposited ITO film, which showed a V_OC of 704 mV. The increase in V_OC could be explained by the decrease in the work function, which is related to the reduction in the barrier height between the ITO and a-Si:H (n) of the rear-emitter SHJ solar cells. Furthermore, the performance of the plasma-treated ITO film was verified, with the front surface field layers, using an AFORS-HET simulation. The current density (J_SC) and V_OC increased to 39.44 mA/cm² and 736.8 mV, respectively, while maintaining a WF_ITO of 3.8 eV. Meanwhile, the efficiency was 22.9% at V_OC = 721.5 mV and J_SC = 38.55 mA/cm² for WF_ITO = 4.4 eV. However, an overall enhancement of 23.75% in the cell efficiency was achieved owing to the low work function value of the ITO film. Ar plasma treatment can be used in transparent conducting oxide applications to improve cell efficiency by controlling the barrier height.     

MoO3/Ag/MoO3 top anode structure for semitransparent inverted organic solar cells

In this study, we fabricated semitransparent polymeric solar cells with an inverted structure, with the structure being indium tin oxide (ITO)/cesium carbonate (Cs₂CO₃)/poly(3-hexylthiophene) (P3HT):1-(3-methoxycarbonyl)propyl-1-phenyl[6,6]C61(PCBM)/transparent multilayer. The structure of the transparent multilayer (DMD multilayer), which acted as the anode, was MoO₃ (1–40 nm)/Ag (10 nm)/MoO₃ (0–80 nm). The inner MoO₃ layer showed a great performance changes depending on the variation of thickness, while the outer MoO₃ layer showed relatively slight changes. The best performance was observed with the of anode DMD multilayer thickness of 6/10/40 nm and with the illumination from the ITO side in organic solar cell devices. High performance result was observed in high reflectance and low transmittance of the DMD layer.