Micro-light-emitting-diode (μLED) displays with low power consumption are highly desirable for the mobile devices powered by batteries. However, since the smaller LED chip size corresponds to lower optical efficiency, this advantage is compromised. In this paper, we develop a model to evaluate the power consumption of micro-LED displays based on ambient contrast ratio. Then, the optimal μLED chip sizes to achieve the lowest power consumption for smartphones, laptop computers, and TVs, are obtained. Furthermore, we propose to employ different RGB chip sizes in μLED displays. In comparison with the optimal results with uniform LED chip size, our new design offers an additional 12% average power saving for real image contents.
Micro-scale light emitting diode (micro-LED) with a chip size less than 100 μm has improved light extraction efficiency due to increased sidewall emission. However, it causes mismatched angular distributions between AlGaInP-based red micro-LED and InGaN-based blue/green counterparts because of the epitaxial material difference. As a result, color shift of RGB micro-LED displays may become visually noticeable. To address this issue, the angular distributions of RGB micro-LEDs are analyzed theoretically and experimentally. In addition, a device structure with top black matrix and taper angle in micro-LEDs is proposed, which greatly suppresses the color shift while keeping a reasonably high light extraction efficiency.
We demonstrate a fast-response liquid crystal display (LCD) with an ultra-low-viscosity nematic LC mixture. The measured average motion picture response time is only 6.88 ms, which is comparable to 6.66 ms for an OLED at a 120 Hz frame rate. If we slightly increase the TFT frame rate and/or reduce the backlight duty ratio, image blurs can be further suppressed to unnoticeable level. Potential applications of such an image-blur-free LCD for virtual reality, gaming monitors, and TVs are foreseeable.
Optical absorption improvement and cost reduction of thin-film solar cells have been long-time issues. These two aims are achieved simultaneously by combining metallic nanoribbons and dielectric gratings at the front side of ultrathin-film amorphous silicon solar cells. Surface-plasmon-polariton waves excited by the nanoribbons at the long wavelength co-operates with Uller-Zenneck waves and cavity resonances excited by the gratings at the short wavelength with little cross-effect, leading to a complementary absorption enhancement of 31% when compared to planar structure. In addition, this design exhibits wide-angle absorption as well as a high fabrication tolerance. Compared to the previous work combining different mechanisms, this design provides fewer fabrication steps and an easier approach. Moreover, the nanoribbons can be used as a transparent conducting electrode for a low-cost alternative to expensive indium tin oxide thin-film.
Thin film absorber structure is becoming one of the hot topics recently for its various sub-wavelength applications such as photo detector, thermo photovoltaic cells, thin-film thermal emitters, and multi-color filters. In this work, we extended the design principles of single band absorbers to tri-band absorbers based on single nanorod unit which exhibits localized surface plasmon resonances (LSPs). By varying the geometric parameters of nanorod arrays, the absorption spectrum can be tailored. Detailed study was carried out by using finite difference time domain (FDTD) method to reveal the mechanism of high absorption. Even broader absorption could be realized based on this work.
A cavity enhanced one-dimensional grating structure is proposed to improve the light absorption within the α-Si thin film solar cell. Typically, dielectric or metal structure including gratings is added for the light absorption enhancement. Not only does the structure form the guided modes, and increase the surface area/surface angle, but also the thin film itself forms a cavity allowing light trapping for better absorption. However, the structure is optimized in these two mechanisms separately. In this paper, finite element method (FEM) was used to optimize thicknesses of two cavities and then combine them into a one –dimensional grating structure. Comparing to the flat thin film solar cell, we have get absorption enhancement factors of 1.12 and 1.51 normalized for the AM 1.5 spectrum for 300 nm to 950 nm by the two proposed structures.
As the desire growing of the thin film absorption structure for various sub-wavelength applications such as photo
detector, thin-film thermal emitters, thermo photovoltaic cells, and multi-color filters, we proposed a type of subwavelength
multi-branch dimers which exhibit several tunable dipole-dipole-like plasmonic resonances and integrated it
into metal-insulator-metal structure as the top layer. The structures are studied through numerical calculation by finite
element method. When normal incident is considered, the novel structure shows three absorption peaks in the considered
wavelength range. One peak has near-perfect absorption and the other two also show excellent absorption.. When
different angle oblique incident is considered, the absorption only has slight change, which is useful to an ultrathin
absorber structure. In addition, we find that the thickness of the dielectric layer can tune the absorption rates for each
absorption peak. In general, the multi-branch dimers can easily tune its absorption rates and spectrum via the change of
their geometric parameters such as branch lengths, branch angles, and dielectric layer thickness.