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Upon optimizing the periodic structures for blue, green and red OLEDs, we fabricate white OLEDs on a corrugated ITO substrate prepared from a specific mixing ratio of PS spheres in different sizes. Eventually, white OLEDs show a significant enhancement in current and power efficiencies. The CIE coordinates are located in a warm white light region even at different viewing angles. [ABSTRACT FROM AUTHOR]

Inter-molecular charge transfer-based donor–acceptor combination – with type-II energy transfer and known as an exciplex – has been extensively studied as a host for organic light-emitting diodes (OLEDs) due to the benefit of high efficiency. However, the broad spectral emission and full width at half maximum (FWHM) of the resulting electroluminescence lead to poor color purity, limiting their potential use in flat panel displays. We here propose a combination strategy that unites an exciplex host and a micro-cavity to resolve the color purity issue. The proposed strategy enables OLEDs to exhibit 2-fold narrower FWHM (26 nm vs. 71 nm) and a record current efficiency (CE) of 180.2 cd A−1 (CE remains 167 cd A−1 at 1000 cd m−2) without any external light-extraction techniques. This work offers a new strategy to achieve high efficiency and high color-purity OLEDs simultaneously. [ABSTRACT FROM AUTHOR]

Trapped light in an organic light-emitting diode (OLED) can be extracted through the construction of periodic structures on the substrates. However, these periodic structures can merely enhance the light emission of a specific wavelength, but not the white light for lighting application. In this work, indium tin oxide (ITO) with a corrugated structure is prepared by reactive ion etching of a polystyrene (PS) sphere matrix with diameters of 300 and 350 nm, which can apparently reduce the losses produced by the waveguide mode and surface plasmon polariton (SPP) mode in the RGB-based white OLED. The extractions of the waveguide mode and SPP mode are investigated theoretically and experimentally. This special corrugated ITO structure with the pitches of 300 and 350 nm, as an internal light out-coupling structure, is useful for the extraction of bluish green and red emission, respectively. More importantly, there are significant enhancements in both the current and power efficiencies of white OLEDs, and the CIE coordinates are located in the warm white region with different viewing angles. Using different weight ratios of the mixed PS spheres, the electroluminescent spectra of white OLEDs can be easily adjusted. [ABSTRACT FROM AUTHOR]

Nano-modified indium tin-oxide (ITO) glass substrates are fabricated for an internal light-extraction structure to enhance the out-coupling efficiency of green organic light-emitting diode (OLED) devices. This nano-modified anode with low haze was prepared by wet chemical etching. Polystyrene (PS) hemispheres, which were distributed randomly on the ITO anode surface, were used as the etching mold. With the help of nano-modified ITO glass substrate, the light trapped by the internal waveguide mode can be extracted effectively compared with conventional planar OLED devices. When OLED devices are incorporated with a nano-modified ITO anode, the highest enhancements of current efficiency (CE), power efficiency (PE) and external quantum efficiency (EQE) are about 40.7%, 37.1% and 36.9%, respectively, relative to a standard device without any light out-coupling structure in the forward direction. To further improve the performance of OLED devices, an ideal microlens array (IMLA) is introduced to the air-side of the glass substrate to extract substrate waveguide. With both internal and external out-coupling structures, the CE, PE and EQE of OLED devices are enhanced by 101.5%, 100% and 96%, reaching 119.3 cd A−1, 108.8 lm W−1 and 31.4% in the forward direction, respectively. Moreover, the nano-modified ITO anode with low haze has no detrimental effect on the performance of OLED devices and is suitable for lighting and display application. [ABSTRACT FROM AUTHOR]

Herein, we show a kind of novel tandem white OLED (WOLED) with interface exciplex, which obtaining a high current efficiency of 40.53 cd/A (EQE=18.15%) without light out‐coupling technology. The WOLEDs generally show simpler device structure and lower working voltage. Moreover, the designed WOELDs generally emit warm white spectrum with low correlative color temperature of 3701K~4699K. [ABSTRACT FROM AUTHOR]

Problem A successful human pregnancy requires cytotrophoblasts from the fetal portion of the placenta to adopt tumor-like properties. But unlike tumor metastasis, cytotrophoblast invasion is highly regulated both spatially and temporally. The mechanisms that regulate human trophoblast invasion are understood poorly. Method of study With a view to obtain some findings on the mechanisms that regulate human trophoblast invasion, we applied the semi-quantitative reverse transcription polymerase chain reaction (RT-PCR) method to compare the expression of invasion-associated genes in cytotrophoblasts isolated from first- and third-trimester placental tissues. Results In trophoblast cells of first-trimester pregnancy, the mRNA contents of matrix metalloproteinase (MMP)-9 and urokinase-type plasminogen activator (uPA) were higher than that in the third-trimester cytotrophoblasts, while no difference of MMP-2 mRNA expression level was found between trophoblastic cells of different gestational ages. The expression level of plasminogen activator inhibitors-1 mRNA in first-trimester cytotrophoblasts was shown to be much lower than that in trophoblast cells prepared from third-trimester placental tissues. Furthermore, expression of both tissue inhibitor of metalloproteinase (TIMP)-1 and TIMP-2 in cytotrophoblasts were significantly up-regulated in third-trimester when compared with the first-trimester of pregnancy. To further investigate the factors that caused the change of invasion-associated genes expression in trophoblast cells, we found that interleukin-10 (IL-10) could decrease the content of MMP-9 mRNA in cytotrophoblasts of first-trimester gestation, and the magnitude of suppression increased with increasing IL-10 concentration. Conclusion The gradually reduced trophoblast invasion with gestational weeks might be on account of the change of proteolytic enzymes/activator/inhibitor genes expression. IL-10 could be one of the factors participating in the regulation of trophoblast invasion during gestational process. [ABSTRACT FROM AUTHOR]