Orange and Red Organic Light‐Emitting Devices Employing Neutral Ru(II) Emitters: Rational Design and Prospects for Color Tuning

A new series of charge‐neutral Ru(II ) pyridyl and isoquinoline pyrazolate complexes, [Ru(bppz)₂(PPh₂Me)₂] (bbpz: 3‐tert‐butyl‐5‐pyridyl pyrazolate) ( 1 ), [Ru(fppz)₂(PPh₂Me)₂] (fppz: 3‐trifluoromethyl‐5‐pyridyl pyrazolate) ( 2 ), [Ru(ibpz)₂(PPhMe₂)₂] (ibpz: 3‐tert‐butyl‐5‐(1‐isoquinolyl) pyrazolate) ( 3 ), [Ru(ibpz)₂(PPh₂Me)₂] ( 4 ), [Ru(ifpz)₂(PPh₂Me)₂] (ifpz: 3‐trifluoromethyl‐5‐(1‐isoquinolyl) pyrazolate) ( 5 ), [Ru(ibpz)₂(dpp?)] (dpp? represents cis‐1,2‐bis‐(diphenylphosphino)ethene) ( 6 ), and [Ru(ifpz)₂(dpp?)] ( 7 ), have been synthesized, and their structural, electrochemical, and photophysical properties have been characterized. A comprehensive time‐dependant density functional theory (TDDFT) approach has been used to assign the observed electronic transitions to specific frontier orbital configurations. A multilayer organic light‐emitting device (OLED) using 24 wt % of 5 as the dopant emitter in a 4,4′‐N,N′‐dicarbazolyl‐1,1′‐biphenyl (CBP) host with 4,4′‐bis[N‐(1‐naphthyl)‐N‐phenylamino]biphenyl (NPB) as the hole‐transport layer exhibits saturated red emission with an external quantum efficiency (EQE) of 5.10 %, luminous efficiency of 5.74 cd A^–1, and power efficiency of 2.62 lm W^–1. The incorporation of a thin layer of poly(styrene sulfonate)‐doped poly(3,4‐ethylenedioxythiophene) (PEDOT) between indium tin oxide (ITO) and NPB gave anoptimized device with an EQE of 7.03 %, luminous efficiency of 8.02 cd A^–1, and power efficiency of 2.74 lm W^–1 at 20 mA cm^–2. These values represent a breakthrough in the field of OLEDs using less expensive Ru(II ) metal complexes. The nonionic nature of the complexes as well as their high emission quantum efficiencies and short radiative lifetimes are believed to be the key factors enabling this unprecedented achievement. The prospects for color tuning based on Ru(II ) complexes are also discussed in light of some theoretical calculations.     

Advances in contrast enhancement for DLP projection displays

Abstract— Increased contrast ratios are essential to the continued success of DLP? products in the marketplace, from rear‐projection televisions and home‐theatre systems to large venue displays and DLP Cinema?. The contrast of DLP projection systems has increased steadily over the past 5 years due to improvements in illumination and projection optics, as well as changes to the DMD itself. The authors will present an overview of the contrast performance of DLP projectors over time as well as describe illumination and projection techniques that optimize the performance of the DMD.     

Nanomaterials‐Based Electrochromics for Paper‐Quality Displays

Electrochromic displays based on nanostructured films modified with electrochromophores are capable of becoming high quality paper‐like displays due to their excellent ink‐on‐paper optical qualities, fast response times, and low power consuming features. The nanostructured films are composed of nanoparticles of a semiconductor, e.g., TiO₂ and other doped metal oxides. The high coloration efficiencies of these devices is due to the use of organic chromophores and the amplification of the color change due to the extremely high surface area of the nanostructured film they are bound to.     

平版印刷法制作电致发光显示器的微型化电极布线

平板印刷柔性的电致发光显示器的交错对插的电极.根据电致发光的荧光粉颗粒尺寸的大小采用的不同的方法将其沉积.小颗粒荧光粉分子可以很容易地与印刷油墨混合.使用这种交错对插电极的柔性显示器不需要透明的导电氧化物作为阳极,容易实现大规模生产,造价低.这种显示器使用 ACEL 可以实现多色彩显示.ACEL 可以发射出从绿光到使用ZnS:Clu,X(X=Cl,Br,I)荧光粉的蓝光,或者是到使用ZnS:Cu,Mn荧光粉的橙光.此外,还可以使用颜色转换材料以产生其他颜色的光.     

A shift in the perception of lightness on image in digital media due to the manifestation of the simultaneous contrast effect

This paper presents the results of the influence of simultaneous contrast effect on the shift in viewer perception of lightness, depending on the display on which the effect is being evaluated in relation to reproduction. By using simultaneous binocular harmonization technique 55 participants had a task of harmonizing the test primary stimuli presented on two different displays with the referential primary stimuli (that were designed as desaturated samples of 50% RTV, and which are surrounded by desaturated secondary stimuli whose values increase from 10% RTV up to 100% RTV) from the reproduction that was made in digital electrophotography technology. By using one-way repeated measures ANOVA with fisher post-hoc, the strength of the simultaneous contrast effect was presented. Results could be used as a model for predicting the intensity of the simultaneous contrast effect on the design solution used in this paper on relation analogue/digital media.     

Preferred position of visual displays relative to the eyes: a field study of visual strain and individual differences

At office workplaces equipped with visual display units (VDU) that were adjustable to various positions relative to the eyes short and long viewing distances from the eyes to the screen were imposed (mean value of about 63 and 92 cm) at two levels of screen height so that the visual target was either at eye level or 18 cm below, on the average. The change from far to near viewing distance produced a larger increase in eyestrain when the VDUs were at eye level. High screens resulted in greater eyestrain than low screens, as shown by correlations over subjects. When operators were free to adjust the most comfortable screen position, the group of 22 participants preferred viewing distances between 60 and 100 cm and vertical inclination of gaze direction between horizontal and - 16° downwards. However, within most subjects the range of preferred screen positions was much smaller. Between 3 days during a 1-month period the test-retest correlations of the preferred screen positions were highly significant, both for viewing distance and vertical gaze inclination. When operators were forced to work at a shorter distance than their preferred viewing distance they reported more visual strain. Thus, operators appear to prefer an individual adjustment of the screen relative to the eyes in order to avoid visual strain and discomfort at VDU work.     

CaMoO4:RE3+,Yb3+,M+ phosphor with controlled morphology and color tunable upconversion

CaMoO₄:RE³⁺,Yb³⁺ (RE = Er, Ho, Tm) phosphors were successfully synthesized by a facile hydrothermal method. XRD patterns confirmed tetragonal structure under different RE³⁺ and M⁺ ions doping conditions. Particles shapes and sizes were confirmed by SEM and TEM analyses. Particles shape and size were well tuned by control of solution pH; spherical balls consisting of nano-grains at low pH of ∼2, rice grain shapes at moderate pH of ∼6, and thin flakes at higher pH of ∼12, were observed. Fine tunability of upconversion (UC) emission color was achieved by doping multiple RE³⁺ ions within a single CaMoO₄ host. Blue, green and orange upconverted emission were observed by doping Tm³⁺, Er³⁺ and Ho³⁺ in the CaMoO₄, respectively. Further, the emission colors were well tuned by the combination of Tm, Er and Ho ions and their concentrations. CaMoO₄:Tm³⁺,Ho³⁺,Yb³⁺ exhibited perfect white emission with well tunability from cool white to warm white colors. Substitution of part of Ca ions by M⁺ (M = Li, Na, K, Rb) ions affected the crystal field symmetry around RE³⁺ ions and hence changed the transition probabilities between their f–f transition levels, consequently intensified the UC intensities. The blue (Tm³⁺), green (Er³⁺), and orange (Ho³⁺) upconversion intensities of CaMoO₄:RE³⁺,Yb³⁺,0.10 K⁺ phosphors increased by 60, 50 and 40 folds compared to the unsubstituted analogues, respectively. The K substituted CaMoO₄:RE³⁺,Yb³⁺,K⁺ phosphors exhibited intense UC emissions visible by naked eye even pumped by less than 1 mW laser power and can have potential application in displays and variety of other applications.