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.     

Plasma-based sputtering of indium tin oxide for the application of photovoltaic cells

Transparent and conducting indium tin oxide (ITO) thin films were deposited on soda lime glass substrates by RF plasma magnetron sputtering at room temperature. The effect of thickness (100, 200 and 300?nm) on the physical (structural, optical, electrical) properties of ITO thin films was investigated systematically. It is observed that with an increase in thickness, the X-ray diffraction data indicate polycrystalline films with grain orientations predominantly along (222) and (400) directions; the average grain size increases from 10 to 30?nm; the optical band gap increases from 3.68 to 3.73?eV and the transmission decrease from 80% to 70% . Four-point probes show a low resistivity (2.4×10^?5?Ω?cm) values for film with a thickness 300?nm. Present work shows that the ITO is a promising transparent conductive oxide material for the solar cell application.     

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.     

Improved device reliability in organic light emitting devices by controlling the etching of indium zinc oxide anode

A controllable etching process for indium zinc oxide （IZO） films was developed by using a weak etchant of oxalic acid with a slow etching ratio. With controllable etching time and temperature, a patterned IZO electrode with smoothed surface morphology and slope edge was achieved. For the practical application in organic light emitting devices （OLEDs）, a sup- pression of the leak current in the current-voltage characteristics of OLEDs was observed. It resulted in a 1.6 times longer half lifetime in the IZO-based OLEDs compared to that using an indium tin oxide （ITO） anode etched by a conventional strong etchant of aqua regia.     

金纳米四面体增强有机太阳电池光吸收及光伏性能研究

为增强有机太阳能电池的光利用率,提高能量转换效率,本文合成了金四面体形状的纳米粒子,并用聚苯乙烯磺酸钠(PSS)包裹形成了核壳结构的金纳米四面体(Au@PSS tetrahedra NPs).将其掺杂到有机太阳能电池空穴提取层与活性层的界面处,利用表面等离子体共振效应来增强活性层对光的吸收,从而提高有机太阳能电池的能量转换效率.研究了掺杂浓度和PSS包裹厚度对电池性能的影响.结果表明:掺杂浓度为6%时,器件性能最佳,能量转换效率达到3.08%; PSS壳层厚度优化为2.5 nm时,转换效率达到3.65%,较标准电池提升了22.9%.电池性能的改善主要源于金四面体纳米粒子的共振吸收峰位于给体材料吸收谱范围内,纳米粒子的共振促进了给体的吸收,同时PSS壳层的引入促进了激子的解离和电荷的转移,上述因素的改善提升了电池的短路电流、填充因子和转换效率.     

The insert of zinc oxide thin film in indium tin oxide anode for organic electroluminescence devices

Zinc oxide films were prepared by rf magnetron sputtering on glass substrates with designed ZnO target using high-purity of zinc oxide (99.99%) powder. Systematic study on dependence of target-to-substrate distance (D_ts) on structural, electrical and optical properties of the as-grown ZnO films was mainly investigated in this work. XRD showed that highly preferred ZnO crystal in the [0 0 1] direction was grown in parallel to the substrate, while the D_ts did not effect to the peak position of XRD. With decreasing D_ts, the growth rate is increased while the electrical resistivity as well as crystal size in the ZnO films was decreased. The XPS data showed that the O/Zn ratio in ZnO films was increased with increasing D_ts in the films. The as-grown ZnO films have an average transmittance of above 85% at the visible region. The optical band gap of the as-grown ZnO films was changed from 3.18 to 3.36 eV with D_ts. With decreasing D_ts, the electrical resistivity was decreased, while the growth rate was increased.A bilayer is used as an anode electrode for organic electroluminescent devices. The bilayer consists of an ultrathin ZnO layer adjacent to a hole-transporting layer and an Indium tin oxide (ITO) outerlayer. We tried to bring low the barrier between the devices as deposited ZnO films on ITO substrates. We fabricated the organic EL structure consisted of Al as a cathode, Al₂O₃ as an electro transport layer, Alq₃ as a luminously layer, TPD as a hole transport layer and ZnO (1 nm)/ITO (150 nm) as an anode. The result of this experiment was not good compared with the case of using ITO, nevertheless, at this structure we obtained the lowest turn-on voltage as the value of 19 V and the good brightness (6200 cd/m²) of the emission light from the devices. Then the quantum efficiency was to be 1.0%.     

Infrared laser-induced fast photovoltaic effect observed in orthorhombic tin oxide film

The SnO_2/SnO with an orthorhombic structure is a material known to be stable at high pressures and temperatures and expected to have new optical and electrical properties. The authors report a new finding of the infrared laser induced a fast photovoltaic effect arising from orthorhombic tin oxide film with an indirect band gap(~2.4 e V) which is deposited by pulsed laser deposition. The rising time of the photovoltaic signal is about 3 ns with a peak value of 4.48 mV under the pulsed laser beam with energy density 0.015 m J/mm~2. The relation between the photovoltages and laser positions along the line between two electrodes of the film is also exhibited. A possible mechanism is put forward to explain this phenomenon.All data and analyses demonstrate that the orthorhombic tin oxide with an indirect band gap could be used as a candidate for an infrared photodetector which can be operated at high pressures and temperatures.     

ITO‐free top emitting organic light emitting diodes with enhanced light out‐coupling

Bottom emitting organic light emitting diodes (OLEDs) can suffer from lower external quantum efficiencies (EQE) due to inefficient out‐coupling of the generated light. Herein, it is demonstrated that the current efficiency and EQE of red, yellow, and blue fluorescent single layer polymer OLEDs is significantly enhanced when a MoO_x(5 nm)/Ag(10 nm)/MoO_x(40 nm) stack is used as the transparent anode in a top emitting OLED structure. A maximum current efficiency and EQE of 21.2 cd/A and 6.7%, respectively, was achieved for a yellow OLED, while a blue OLED achieved a maximum of 16.5 cd/A and 10.1%, respectively. The increase in light out‐coupling from the top‐emitting OLEDs led to increase in efficiency by a factor of up to 2.2 relative to the optimised bottom emitting devices, which is the best out‐coupling reported using solution processed polymers in a simple architecture and a significant step forward for their use in large area lighting and displays.     

Attachment of gold nanoparticles onto indium tin oxide surfaces controlled by adding citrate ions in a seed-mediated growth method

A simple approach to control the attachment of gold nanoparticles (AuNPs) onto the indium tin oxide (ITO) surfaces is reported. Adjusting the concentration of trisodium citrate in the Au colloid solution for the seeding process from 1 to 50 mM in the seed-mediated growth method, the dramatic changes in the SEM images and actual color were observed indicating the changes in nanostructures of AuNPs formed on the ITO surfaces. Whereas the attachment of smaller AuNPs with higher density were observed when 25 mM citrate ions were added in the seed solution, larger AuNPs were observed to attach at 50 mM. On the basis of this difference and the surface SEM images observed just after seeding, the roles of citrate ions were discussed. Consequently, it was inferred that the citrate ions affected the growth process as well as the seeding process. The repulsive power expected from the increased negative charges of citrate ions were not significant, but rather the dense attachment was promoted as the peculiar effect of citrate ions. Such control of the AuNPs attachment on ITO would be practically effective because the dense attachment can be performed by just changing the composition of the seed solution.     

Effect of NO annealing on charge traps in oxide insulator and transition layer for 4H-SiC metal–oxide–semiconductor devices

The effect of nitric oxide(NO) annealing on charge traps in the oxide insulator and transition layer in n-type4H–Si C metal–oxide–semiconductor(MOS) devices has been investigated using the time-dependent bias stress(TDBS),capacitance–voltage(C–V),and secondary ion mass spectroscopy(SIMS).It is revealed that two main categories of charge traps,near interface oxide traps(Nniot) and oxide traps(Not),have different responses to the TDBS and C–V characteristics in NO-annealed and Ar-annealed samples.The Nniotare mainly responsible for the hysteresis occurring in the bidirectional C–V characteristics,which are very close to the semiconductor interface and can readily exchange charges with the inner semiconductor.However,Not is mainly responsible for the TDBS induced C–V shifts.Electrons tunneling into the Not are hardly released quickly when suffering TDBS,resulting in the problem of the threshold voltage stability.Compared with the Ar-annealed sample,Nniotcan be significantly suppressed by the NO annealing,but there is little improvement of Not.SIMS results demonstrate that the Nniotare distributed within the transition layer,which correlated with the existence of the excess silicon.During the NO annealing process,the excess Si atoms incorporate into nitrogen in the transition layer,allowing better relaxation of the interface strain and effectively reducing the width of the transition layer and the density of Nniot.