Low out-coupling efficiency is one of the most critical problems in organic light-emitting device (OLED) application.
Only 20~30% of the emitting light from OLED can propagate into air . Therefore, several methods have been utilized
to extract more light from device. Here, we use the microlens array attached on device to couple out wave-guiding mode
in the glass substrate. We found that, the luminous enhancement behavior has great dependence on OLED structure.
When light emitted in the layered structure of OLED, the wide angle interference and multi-beam interference occurred,
and far-field emission profile change simultaneously. For different emission profile, microlens array film shows a
different enhancement behavior. For a conventional OLED device, the most critical interference will occur at the
electron transport layer (ETL). We fabricated a series of OLEDs with different ETL thicknesses to investigate the
influence to the optical properties, such as spectrum, CIE coordinate change, and emission profile at different view
angles. By controlling the emission dipole position, we investigate the relation between the emission profile and the
efficiency enhancement by microlens array attachment. When increasing the ETL thicknesses from 30nm to 150nm, the
weaker micro cavity effect results in broader spectrum and more light extracted. In these devices, the luminous
enhancement varies from 25.1% to 51.3%.
We investigated the luminance enhancement, spectral shift and image blur of the OLED with the microlens array
film (MAF) attachment experimentally and theoretically. Higher density, larger curvature, and smaller diameter of the
microlenses extracted more light from the substrate mode. The maximum improvements of the luminance at the normal
direction and the total power were 42.5% (80%) and 45% (85%) from our experimental (simulation) results, respectively.
The differences between the theoretical and experimental results may come from the non-Lambertian radiation of OLED
and the imperfection of the microlens array film. From observing the planar OLED, the peak wavelength is blue-shifted
and the full width at the half maximum (FWHM) decreased with respect to increasing viewing angles due to the
microcavity effect. When the MAF was attached, the spectral peak had a further blue shift (5 to 10 nm at different
viewing angles) compared to that of the planar OLED and it came from the light extraction of the MAF from the
We also quantitatively investigated the "blur width" of the OLED with MAF attachment. Higher image blur was
observed as accompanied with higher extraction efficiency which showed a tradeoff between the image quality and
extraction efficiency. It means that the MAF attachment is more suitable for OLED lighting application, rather than
display application. To reduce the image blur and keep the high extraction efficiency at the same time, we re-designed
the arrangement of the microlens arrays on the film. In our optimized case, we found that the blur width can be reduced
from 79 μm to 9 μm, while the extraction efficiency is kept nearly the same. It shows a possibility to use the microlens
array film on real OLED display for improving the extraction efficiency without image quality degradation.
This study proposed a novel approach to replace the traditional surface plasmon resonance (SPR) bulk prism by
microlens arrays (MLAs). It demonstrated the effect that coupling SPR on the optical response of microlens arrays
structure. Surface plasmons are features specific to the interface of metal-dielectric. They are due to charge density
oscillations in the metal, accompanied by electromagnetic field dissipation in the metal and in the dielectric. SPR
biosensor bulk prism technology has been commercialized and SPR biosensors have become a central tool for
characterizing and quantifying biomolecular interactions. We will used this microlens arrays coupling SPP phenomenon,
which gives rise to selective spectral response due to a local field enhancement interrelating the optical and biochemical
In this paper, we have demonstrated a low-reflectance organic light-emitting device (OLED) by inserting a perylene
diimide derivative between the emitting layer (EML) and the cathode. Such a material exhibits a good electron transport
capability and good photoconductivity which absorbs light. A semi-transparent layer composed of thin aluminum (Al)
and silver (Ag) was used between the EML and the n-type organic material, a perylene diimide derivative, for better
electron injection and efficient destructive interference. The J-V characteristics of our low reflection and the control one
are nearly identical which shows the superior conductivity of this material. In addition, the absorption peak of this ntype
organic material is near 550 nm which can eliminate most of the ambient visible light. And the potocurrent is
generated from self-absorption by this material. Thus, this device can also be applied as a photodetector or the
applications of the self-adjustable display under different ambient illumination with suitable driving scheme.
In this paper, We have demonstrated a blue fluorescent organic light-emitting device (OLED) with a current efficiency
of 19.2 cd/A at 100 cd/m2, an estimated half-lifetime of 15611 hours at an initial luminance of 1000 cd/m2, and a voltage
of 4.9 V at 20 mA/cm2 with a high electron mobility electron transport layer (ETL) material and high efficiency dopant
material. The external quantum efficiency (EQE) in this optimized OLED is 8.32%, which is very close to the
theoretical limit. Carrier balance condition is achieved due to the incorporation of the high mobility ETL, bis(10-
hydroxyben-zo[h]quinolinato)beryllium (Bebq2), which can not only effectively increase the current efficiency and
elongate the operation lifetime, but also reduce the driving voltage and increase the power efficiency. The EML
consisted of 4,4'-bis[2-(4-(N,N-diphenylamino)phenyl)vinyl]biphenyl (DPAVBi) as the blue dopant and 9,10-bis(2'-
naphthyl) anthracene (ADN) as the matrix. We found that the dopant concentration of DPAVBi did not affect the
mobility value of the EML which is consistent with the J-V characteristics. Besides, although it is believed the bulk
ADN is a kind of HTL materials, we found the electron mobility of ADN is one order of magnitude higher than its hole
mobility in our blue OLEDs.
We propose a fast coarse-to-fine video retrieval scheme using shot-level spatio-temporal statistics. The proposed scheme consists of a two-step coarse search and a fine search. At the coarse-search stage, the shot-level motion and color distributions are computed as the spatio-temporal features for shot matching. The first-pass coarse search uses the shot-level global statistics to cut down the size of the search space drastically. By adding an adjacent shot of the first query shot, the second-pass coarse-search introduces the "causality" relation between two consecutive shots to improve the search accuracy. As a result, the final fine-search step based on local color features of key-frames of the query shot is performed to further refine the search result. Experimental results show that the proposed methods can achieve good retrieval performance with a much reduced complexity compared to single-pass methods.