Near Infrared Electoluminescence of Er—doped ZnS Thin Film Devices

Near infrared electroluminescence characteristics of the Er-doped ZnS thin film devices,fabricated by thermal evaporation with two doats,are reported.The study of the film microstructure has been carried out using X-ray diffraction.The effects of the E-rdoped film microstructure on luminescence are pointed out.     

Influence of Cu_xS back contact on CdTe thin film solar cells

We present a detailed study on CuxS polycrystalline thin films prepared by chemical bath method and utilized as back contact material for CdTe solar cells.The characteristics of the films deposited on Si-substrate are studied by XRD.The results show that as-deposited CuxS thin film is in an amorphous phase while after annealing,samples are in polycrystalline phases with increasing temperature.The thickness of CuxS thin films has great impact on the performance of CdS/CdTe solar cells.When the thickness of the film is about 75 nm the performance of CdS/CdTe thin film solar cells is found to be the best.The energy conversion efficiency can be higher than 12.19%,the filling factor is higher than 68.82% and the open-circuit voltage is more than 820 mV.     

Research on the properties of ZnO1-xSx thin films modified by sulfur doping for CIGS solar cells

ZnO1-xSx thin films modified by sulfur doping were prepared on glass substrates by chemical bath deposition (CBD) for studying the effect of thiourea concentration on the thin film properties. The obtained ZnO1-xSx thin films were characterized by scanning electron microscopy (SEM), which shows the surfaces of ZnO1-xSx thin films deposited under the thiourea concentration of 0.14 M are more compact. X-ray diffraction (XRD) measurement shows that the ZnO1-xSx thin films with hexagonal crystal structure had strong diffraction peaks and better crystallinity. The optical transmittance of the ZnO1-xSx thin films with 0.14 M thiourea concentration is above 80% in the wavelength range of 300—900 nm. According to the measurement results from spectrophotometer, the ZnO1-xSx band gap energy value Eg varies nonlinearly with different S/(S+O) ratio x, and increases with the increase of x. There is a band gap value of 2.97 eV in the ZnO1-xSx thin films deposited under 0.14 M thiourea concentration. Therefore, the thin films have better structural, optical and electric properties, and are more suitable for the buffer layers of copper indium gallium selenide (CIGS) thin film solar cells.     

The TCR of Ni24.9Cr72.5Si2.6 thin films deposited by DC and RF magnetronsputtering

The temperature coefficient of resistance (abbreviated as TCR) of thin film resistors on some sensor chips,such as thermal converters,should be less than several ppm/℃.However,the TCR of reported thin films is larger than 5 ppm/℃.In this paper,Ni_24.9Cr_72.5Si_2.6 films are deposited on silicon dioxide film by DC and RF magnetron sputtering.Then as-deposited films are annealed at 450℃ under different durations in N₂ atmosphere. The sheet resistance of thin films with various thickness and annealing time are measured by the four probe resistivity test system at temperature of 20,50,100,150,and 200℃ and then the TCR of thin films are calculated. Experimental results show that the film with the TCR of only-0.86 ppm/℃ can be achieved by RF magnetron sputtering and appropriate annealing conditions.     

TiO2 Thin Film UV Detectors Deposited by DC Reactive Magnetron Sputtering

CrystallineTiO2 thin films were prepared by DC reactive magnetron sputtering on indium--tin oxide(ITO) thin film deposited on quartz substrate, the photoconductive UV detector on TiO2 thin films was based on a sandwich structure of C/TiOz/ITO. The measurement of the I—V characteristics for these devices shows good ohmic contact. The photoresponse of TiO2 thin films was analyzed at different bias voltage. The detector shows a good photoresponse with a rise time of 2 s and a fall time of 40 s, the photocurrent is linearly increased with the bias voltage.     

Microwave annealing effects on ZnO films deposited by atomic layer deposition

Zinc oxide thin films deposited on glass substrate at 150°C by atomic layer deposition were annealed by the microwave method at temperatures below 500 °C.The microwave annealing effects on the structural and luminescent properties of Zn O films have been investigated by X-ray diffraction and photoluminescence.The results show that the MWA process can increase the crystal quality of Zn O thin films with a lower annealing temperature than RTA and relatively decrease the green luminescence of Zn O films.The observed changes have demonstrated that MWA is a viable technique for improving the crystalline quality of Zn O thin film on glass.     

Effect of the Structure and Valence State on the Properties of VO2 Thin Films

VO2 thin films with good switching properties were prepared by controlling the annealing time and the annealing temperature in a vacuum system.The structural,optical and electrical properties of the samples were cahracterized by using XRD,XPS,UV-VIS and electrical measurements.The witching parameters of VO2 thin film were investigated too.The results indicate that before and after phase transition the resistance of VO2 thin films changes aobut three orders of magnitude,the variation of film transmittance of 40% has been carried out with the absorptivity switching velocity of about 0.2607/min at 900 nm.The structural property of samples has been improved but the phase-transition properties have been decreased by increasing the annealing time and annealing temperature.The valence of V ions and the structure of samples have great effect on phase transition properties of VO2 thin films.Discussion on the effecs of annealing time and annealing temperature on the phase-transition temperature and hysteresis width shows that the best reasonable annealing tiem and annealing temperatre can be achieved.     

Effects of discharge power on the structural and optical properties of TGZO thin films prepared by RF magnetron sputtering technique

The transparent semiconductors of Ti and Ga-incorporated ZnO (TGZO) thin films were prepared by radio frequency (RF) magnetron sputtering onto glass substrates. The effects of discharge power on the physical properties of thin films are studied. Experimental results show that all nanocrystalline TGZO thin films possess preferential orientation along the (002) plane. The discharge power significantly affects the crystal structure and optical properties of thin films. When the discharge power is 200 W, the TGZO thin film has the optimal crystalline quality and optical properties, with the narrowest full width at half-maximum (FWHM) of 1.76´10-3 rad, the largest average grain size of 82.4 nm and the highest average transmittance of 84.3% in the visible range. The optical gaps of thin films are estimated by the Tauc’s relation and observed to increase firstly and then decrease with the increase of the discharge power. In addition, the optical parameters, including refractive index, extinction coefficient, dielectric function and dissipation factor of the thin films, are determined by optical characterization methods. The dispersion behavior of the refractive index is also analyzed using the Sellmeier’s dispersion model.     

硫化锌交流电致发光薄膜结构与特性研究

用电子束研制不同介质膜作绝缘层的掺铒硫化锌交流电致发光薄膜器件,用Ｘ射线衍射技术测量薄膜表面结构,发现薄膜多晶的沉积有择优取向的趋势。观察不同绝缘层交流电致发光器件的初始稳定过程,讨论绝缘层质量对交流电致发光器件的影响。     

溅射制备ZnS:Er~(3+)薄膜的光电子发射结构

利用射频磁控溅射法制备掺铒硫化锌直流电致发光薄膜，用ＸＰＳ（ｘ射线光电子能谱）技术进行剖析，获得薄膜内部构态与发光性能关系的信息，讨论了微晶薄膜中稀土掺杂状态对激发机制的影响。     

Direct formation of β phase in polyoctylfluorene thin film via solvent vapor assisted spin-coating method

Polyoctylfluorene thin films were made using novel solvent vapor assisted spin-coating method, which adds solvent into spin-coater and seal it for several minutes before spin-coating to form a solvent vapor atmosphere. The absorption, photoluminescence spectra, electroluminescence spectra and X-ray diffraction patterns demonstrate that β phase directly generate in such thin film while the thin film made by using normal method is amorphous, which means such method combines normal spin-coating and solvent vapor annealing together into one simply and fast process. The brightness and efficiency of related electroluminescence device are also enhanced due to the self-dopant effect.     

Study on Surface States of Zinc Sulfide Electroluminescence Thin Films

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Morphology and Field‐Effect‐Transistor Mobility in Tetracene Thin Films

The growth of vacuum‐sublimed tetracene thin films on silicon dioxide has been investigated from the early stages of the process. The effects of deposition flux and substrate silanization on film morphology and electrical properties have been explored. Tetracene shows an island growth, resulting in films with a granular structure. Both an increase in the deposition flux and the substrate silanization determine a decrease of the grain size and an improvement of the connectivity of the film in direct contact with the substrate. The hole mobility in field‐effect transistors based on tetracene thin films, which also generate electroluminescence, increases with the deposition flux and values as high as 0.15 cm² V^–1 s^–1 are obtained.     

Control of emission outcoupling in liquid-crystalline fluorescent polymer films

We report the improvement of light outcoupling efficiency of thermally annealed thin liquid crystalline light-emitting polymer films. Unlike the generally observed phenomena from thermally annealed fluorescent polymer films, in the liquid-crystalline fluorescent polymer (LCFP) films, the transverse electric waveguide mode was suppressed due to the light scattering by liquid-crystalline domains in the film. In addition, the optical anisotropy of the annealed LCFP was increased. As a result, the light extraction of photoluminescence and electroluminescence emission in the annealed LCFPs was enhanced by ∼2 times because the emitted light loss by waveguide was minimized. This approach to improve light extraction by forming scattering domains inside the LCFP film gives an insight to improve the outcoupling efficiency of the EL devices in the viewpoint of the material design and film morphologies without employing external geometric device structures.     

Near Infrared Electroluminescence of Er-doped ZnS Thin Film Devices

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Enhancement of hole injection with an ultra-thin Ag2O modified anode in organic light-emitting diodes

The interface between the organic layer and the Indium Tin Oxide (ITO) layer of an organic light-emitting diode (OLED) is crucial to the performance of the device. An ultra-thin Ag₂O film, used as an anode modification layer, has been employed on ITO surface through the UV-ozone treatment of Ag films. The insertion of this thin film with higher work function enhances the hole injection in the organic light-emitting diode and improves the performance of the devices effectively. The maximum electroluminescence (EL) efficiency of the device with the Ag₂O film is 4.95 cd/A, it is about 60% higher than that of the device without it.     

Thermal annealing effect on light emission profile of polyfluorenes containing double bond subunit

We presented comprehensive photoluminescence (PL) and electroluminescence (EL) studies of polyfluorene based electroactive polymer (SF4) containing double bond side chain to investigate its characteristics as a function of temperature. Annealing treatment was conducted for thin films on glass substrates and also for the organic light emitting diodes (OLEDs) at different temperatures. While polymer thin film coated on to glass substrate annealed at < 150 °C exhibited green color emission, OLEDs that annealed at >150 °C shifted white color emission. It was implying that the emission was taking place interchain interaction. Phase modulation at higher annealing temperatures was occurred on the thin film as shown AFM images. Further, annealed polymer film with 120 °C exhibited the best performance in OLED device with luminance 5241 cd m⁻², a maximum efficiency 1.54 cd A⁻¹ and external quantum efficiency 0.54% compared to other polymer films annealed with different temperatures.