Enhanced Efficiency of Metamorphic Triple Junction Solar Cells for Space Applications

Metamorphic In0.55Ga0.45P/In0.06Ga0.94As/Ge triple-junction （3J-MM） solar cells are grown on Ge （100） sub- strates via metal organic chemical vapor deposition. Epi-structural analyses such as high resolution x-ray diffrac- tion, photoluminence, cathodoluminescence and HRTEM are employed and the results show that the high crystal quality of 3J-MM solar cells is obtained with low threading dislocation density of graded buffer （an average value of 6.8× 10^4/cm2）. Benefitting from the optimized bandgap combination, under one sun, AM0 spectrum, 25℃ conditions, the conversion efficiency is achieved about 32%, 5% higher compared with the lattice-matched In0.49Ga0.51P/In0.01Ga0.99As/Ge triple junction （3J-LM） solar cell. Under 1-MeV electron irradiation test, the degradation of the EQE and I-V characteristics of 3J-MM solar cells is at the same level as the 33-LM solar cell. The end-of-life efficiency is -27.1%. Therefore, the metamorphic triple-junction solar cell may be a promising candidate for next-generation space multi-junction solar cells.

A Facile Route to Cotton-Like BiOCl Nanomaterial with Enhanced Dye-Sensitized Visible Light Photocatalytic Efficiency

A facile route is developed to fabricate BiOCI porous cotton-like nanostructure by using Bi203 and hydrochlo- ric acid as raw materials. The BiOCI nanomaterial is actually hierarchically structured by numerous ultrathin nanosheets. The nanosheets are around 50-500 nm in lateral size and 2-12 nm in thickness. High-resolution trans- mission electron microscopy and selected-area electron diffraction analyses indicate that single-crystalline BiOCl nanosheets have the predominant growth direction along [110], the bottom and top surfaces are {001} facets, and four lateral surfaces are {110} facets. The BiOCl nanosheets are dominantly enclosed by {001} facets. From the diffuse reflectance spectroscopy spectrum, the light absorption edge and band gap energy （Eg） are estimated to be 416 nm and 2.98eV, respectively. The BiOCl photocatalyst possesses superior activity for methyl orange （MO） degradation under visible light irradiation and the photodegradation efficiency is up to 91.5%/180 min. The correlation between morphology and microstructure with enhanced MO-sensitized photodegradation performance under visible light is investigated.

Efficiency of Blue Organic Light-emitting Diodes Enhanced by Employing an Exciton Feedback Layer

We report that a novel exciton feedback effect is observed by introducing the bis（2-methyl-8-quinolinolato）（4- phenylphenolato）Muminum （BAlq） inserted between the emitting layer （EML） and the electron transporting layer in blue organic light emitting diodes. As an exciton feedback layer （EFL）, the BAlq does not act as a traditional hole blocking effect. The design of this kind of device structure can greatly reduce excitons＇ quenching due to accumulated space charge at the exciton formation interface. Meanwhile, the non-radiative energy transfer from EFL to the EML can also be utilized to enhance the excitons＇ formation, which is confirmed by the test of photolumimescent transient lifetime decay and electroluminescence enhancement of these devices. Accordingly, the optimal device presents the improved performances with the maximum current efficiency of 4.2 cd/A and the luminance of 24600cd/m2, which are about 1.45 times and 1.75 times higher than those of device A （control device） without the EFL, respectively. Simultaneously, the device shows an excellent color stability with a tiny offset of the CIE coordinates （△x = ±0.003, △y = ±0.004） and a relatively lower efficiency roll-off of 26.2% under the driving voltage varying from 3 V to 10 V.

Broadband Dual-Input Doherty Power Amplifier Design Based on a Simple Adaptive Power Dividing Ratio Function

In this paper,a simple adaptive power dividing function for the design of a dual-input Doherty power amplifier(DPA)is presented.In the presented approaches,the signal separation function(SSF)at different frequency points can be characterized by a polynomial.And in the practical test,the coefficients of SSF can be determined by measuring a small number of data points of input power.Same as other dualinput DPAs,the proposed approach can also achieve high output power and back-off efficiency in a broadband operation band by adjusting the power distribution ratio flexibly.Finally,a 1.5-2.5 GHz highefficiency dual-input Doherty power amplifier is implemented according to this approach.The test results show that the peak power is 48.6-49.7d Bm,and the 6-d B back-off efficiency is 51.0-67.0%,and the saturation efficiency is 52.4-74.6%.The digital predistortion correction is carried out at the frequency points of 1.8/2.1GHz,and the adjacent channel power ratio is lower than-54.5d Bc.Simulation and experiment results can verify the effectiveness and correctness of the proposed method.

A simple unilateral homogenous PhOLEDs with enhanced efficiency and reduced efficiency roll-off

In this paper, highly efficient phosphorescent organic lighting emitting diodes （PhOELDs） with low efficiency roll-off are demonstrated by using a unilateral homogenous device structure with wide band-gap material 4, 4＇, 4＂-tri（N-carbazolyl）-triphenylamine （TCTA） as hole transporting layer and emitting layer （EML）. The opti- mized blue device exhibits a high power efficiency of 40 lm/W, external quantum efficiency of 19.2% and current efficiency of 37.7cd/A. More importantly, the device exhibits a low efficiency roll-off at 1000 cd/m^2. In addition, the white homogenous PhOLEDs only exhibits the efficiency roll-off 5.6% and 17.5%, corresponding to the brightness of 1000 and 5000cd/m^2 respectively. These interesting results demonstrate that the simple unilateral homogenous device structure is a promising way to enhance the device efficiency and reduce the efficiency roll-off.

A systematic study on efficiency enhancements in phosphorescent green, red and blue microcavity organic light emitting devices

A systematic study has been conducted on microcavity organic light emitting diodes(OLEDs)based on green,red and blue phosphorescent emitters to elucidate the microcavity effects for different color emitters.We found that the luminance output is determined by the reflectivity of the semitransparent electrode and the photopic response of the green,red and blue emitters.While the luminance enhancements of blue and red phosphorescent microcavity devices are small,a current efficiency as high as 224 cd A21 is obtained in the green phosphorescent microcavity OLEDs.

Ballistic limit and residual velocity of PELE penetrating against metal target

Based on analyzing the conservation of energy of penetrator with enhanced lateral efficiency （PELE） the penetrating against metal target, a theoretical expression predicting the residual velocity of PELE perforating the target is obtained. By modifying De Marre semi-experience formula,the ballistic limit velocities of PELE penetrating into 2024 aluminum alloy and 45# steel targets are also given. The theoretical predictions fit well with experimental or simulative results.

High Initial Reversible Capacity and Long Life of Ternary SnO_(2)-Co-carbon Nanocomposite Anodes for Lithium-Ion Batteries

The two major limitations in the application of SnO_2 for lithium?ion battery(LIB) anodes are the large volume variations of SnO_2 during repeated lithiation/delithiation processes and a large irreversible capacity loss during the first cycle, which can lead to a rapid capacity fade and unsatisfactory initial Coulombic e ciency(ICE). To overcome these limitations, we developed composites of ultrafine SnO_2 nanoparticles and in situ formed Co(CoSn) nanocrystals embedded in an N?doped carbon matrix using a Co?based metal–organic framework(ZIF?67). The formed Co additives and structural advantages of the carbon?confined SnO_2/Co nanocomposite e ectively inhibited Sn coarsening in the lithiated SnO_2 and mitigated its structural degradation while facilitating fast electronic transport and facile ionic di usion. As a result, the electrodes demonstrated high ICE (82.2%), outstanding rate capability(～ 800 mAh g^(-1) at a high current density of 5 A g^(-1)), and long?term cycling stability(～ 760 mAh g^(-1) after 400 cycles at a current density of 0.5 A g^(-1)). This study will be helpful in developing high?performance Si(Sn)?based oxide, Sn/Sb?based sulfide, or selenide electrodes for LIBs. In addition, some metal organic frameworks similar to ZIF?67 can also be used as composite templates.

Enhanced efficiency and brightness in organic lightemitting devices with MoO_3 as hole-injection layer

The organic light-emitting devices(OLEDs) using 4,4',4''-tris{N-(3-methylphenyl)-N-phenylamin}triphenylamine(m-MTDATA) and MoO_3 or 1,3,5-triazo-2,4,6-triphosphorine-2,2,4,4,6,6-tetrachloride(TAPC) and MoO_3 as the hole-injection layer(HIL) were fabricated. MoO_3 can be expected to be a good injection layer material and thus enhance the emission performance of OLED. The highest occupied molecular(HOMO) of MoO_3 is between those of m-MTDATA or TAPC and N,N'-bis-(1-naphthyl)-N,N'-diphenyl-1,1'-biphenyl-4,4'-diamine(NPB),which reduces the hole-injection barrier and improves the luminance of the OLEDs. The current efficiency is improved compared with that of the device without the MoO_3 layer. The highest luminous efficiency of the device with 2-nm-thick MoO_3 as HIL is achieved as 5.27 cd/A at 10 V,which is nearly 1.2 times larger than that of the device without it. Moreover,the highest current efficiency and power efficiency of the device with the structure indium-tin oxide(ITO)/TAPC(40 nm)/MoO_3(2 nm)/Tc Ta:Ir(ppy)3(10%,10 nm)/ tris-(8-hydroxyquinoline) aluminium(Alq)(60 nm)/Li F(1 nm)/Al are achieved as 37.15 cd/A and 41.23 lm/W at 3.2 V and 2.8 V,respectively.

Enhancement of light extraction efficiency in OLED with two-dimensional photonic crystal slabs

Light extraction efficiency of organic light emitting diode （OLED） based on various photonic crystal slab （PCS） structures was studied. By using the finite-difference time-domain （FDTD） method, we investigated the effect of several parameters, including filling factor and lattice constant, on the enhancement of light extraction efficiency of three basic PCSs, and got the most effective one. Two novel designs of ＂interlaced＂ and ＂double-interlaced＂ PCS structures based on the most effective basic PCS structure were introduced, and the ＂interlaced＂ one was proved to be even more efficient than its prototype. Large enhancement of light extraction efficiency resulted from the coupling to leaky modes in the expended light cone of a band structure, the diffraction in the space between columns, as well as the strong scattering at indium-tinoxide/glass interfaces.

Tapering-induced enhancement of light extraction efficiency of nanowire deep ultraviolet LED by theoretical simulations

A nanowire(NW) structure provides an alternative scheme for deep ultraviolet light emitting diodes(DUV-LEDs)that promises high material quality and better light extraction efficiency(LEE). In this report, we investigate the influence of the tapering angle of closely packed Al Ga N NWs, which is found to exist naturally in molecular beam epitaxy(MBE) grown NW structures, on the LEE of NW DUV-LEDs. It is observed that, by having a small tapering angle, the vertical extraction is greatly enhanced for both transverse magnetic(TM) and transverse electric(TE) polarizations. Most notably, the vertical extraction of TM emission increased from 4.8% to 24.3%,which makes the LEE reasonably large to achieve high-performance DUV-LEDs. This is because the breaking of symmetry in the vertical direction changes the propagation of the light significantly to allow more coupling into radiation modes. Finally, we introduce errors to the NW positions to show the advantages of the tapered NW structures can be projected to random closely packed NW arrays. The results obtained in this paper can provide guidelines for designing efficient NW DUV-LEDs.

Enhanced efficiency and stability of triple-cation perovskite solar cells with CsPbI_(x)Br_(3−x)QDs“surface patches”

Perovskite solar cells(PSCs)with a light-harvesting three-dimensional perovskite bulk layer as backbone component have achieved great progress in performance.Nonradiative recombination is one major place to improve efficiency and stability as they cause significant energy loss in PSCs.Additionally,an imperfection in grain boundaries will initiate device degradation.One of the most successful strategies to decrease nonradiative recombination in PSCs is the introduction of reduced dimensional perovskite(e.g.,perovskite quantum wells),benefiting the device's efficiency and stability tremendously.Here,instead of quantum wells,mixed-cation perovskites with ligand-contained CsPbBr_(x)I_(3−x)quantum dots(QDs)are prepared,which is shown to function as perovskite healing“surface patches.”Benefiting from the“surface patches”effect,the QDs-film shows reduced defects and enhancing film quality which lead to the excellent performance of solar cells(enhancing the power conversion efficiency from 19.21%of the control device to 21.71%[22.1%in reverse scan]).

Improving Nitrogen Use Efficiency in Rice through Enhancing Root Nitrate Uptake Mediated by a Nitrate Transporter, NRT1.1B

Nitrogen （N） is one of most important nutrients for crop production, which makes up 1%-5% of total plant dry matter （Marschner, 2012）. Due to the limited availability of N in soil, application of N fertilizers has been an important agronomic practice to increase crop yield. However, over-application of N fertilizers has caused pollution of N in soil, water and air. It was estimated that the nitrogen use efficiency （NUE, the total biomass or grain yield produced per unit of applied fertilizer N） in cereal crops is as low as 33% （Raun and Johnson, 1999）. Therefore, improving NUE together with reducing application of N fertilizers is an important issue for environment and sustainable production of crops. This is especially important for rice, which is a staple food for half population in the world.

Multi-mode multi-band power amplifier module with high low-power efficiency

Increasingly, mobile communications standards require high power efficiency and low currents in the low power mode. This paper proposes a fully-integrated multi-mode and multi-band power amplifier module （PAM） to meet these requirements. A dual-path PAM is designed for high-power mode （HPM）, medium-power mode （MPM）, and low-power mode （LPM） operations without any series switches for different mode selection. Good performance and significant current saving can be achieved by using an optimized load impedance design for each power mode. The PAM is tapeout with the InGaP/GaAs heterojunction bipolar transistor （HBT） process and the 0.18-μm complementary metal-oxide semiconductor （CMOS） process. The test results show that the PAM achieves a very low quiescent current of 3 mA in LPM. Meanwhile, across the 1.7-2.0 GHz frequency, the PAM performs well. In HPM, the output power is 28 dBm with at least 39.4% PAE and 240 dBc adjacent channel leakage ratio 1 （ACLR1）. In MPM, the output power is 17 dBm, with at least 21.3% PAE and -43 dBc ACLR1. In LPM, the output power is 8 dBm, with at least 18.2% PAE and -40 dBc ACLR1.

Facile and robust strategy to antireflective photo-curing coating through self-wrinkling

We reported a facile and bio-inspired strategy for obtaining antireflective （AR） coating through polymerization-induced self-wrinkling. Upon irradiation of light, the complex wrinkle micro-patterns with different morphologies were generated spontaneously on the surface of coating during photo-cross- linking, which enables the photo-curing coating can decrease reflection. The resulting photo-curing coating exhibits a high transmittance over 90% and low reflection below 5% ～ 8%, with an efficiency anti- reflection of 4% ～ 7%; compared to the flat blank coating. The successful application of these AR coatings with wrinkles pattern to encapsulate the thin film solar cells results in appreciable photovoltaic performance improvement of more than 4% ～ 8%, which benefits from the decrease of the light reflection and increase of optical paths in the photoactive layer by the introduction of wrinkling pattern. Furthermore, the efficiency improvements of the solar cells are more obvious, with a remarkable increase of 8.5%, at oblique light incident angle than that with vertical light incident angle

Multispectral harvesting rare-earth oxysulphide based highly efficient transparent luminescent solar concentrator

Transparent luminescent solar concentrator(LSC)is extensively regarded as the most promising sunlight tapping device for its application in buildings integrated with photovoltaics(BIPV)or as solar window glass.Conventional LSCs doped with organic dyes suffered from high reabsorption losses with no transparency;whereas,recently reported heavy metal-doped quantum dots avoided such losses but possessed the risk of high toxicity and low ambient stability.Thus,luminophores with massive spectral shifts and co rdial relationships with the enviro nment are very much desirable.In this paper,we report the fabrication of PMMA based transparent LSC embedded with nanocrystals of environmental friendiness and multispectral harvesting gadolinium oxysulphide(Gd_(2)O_(2) S:Er,Yb)fluorophore.The Gd_(2)O_(2) S:Er,Yb nanofluorophore absorbs various excitation wavelengths ranging from UV to NIR and emits in the visible region offering huge Stoke’s and anti-Stoke’s shift concurrently.The non-existent reabsorption losses and overlapping maxima of Gd_(2)O_(2) S:Er,Yb nanofluorophore generated photon flux with solar cells’responsivity enhance the efficiency characteristics of the LSC waveguide.Performance analysis of LSC as a function of varying nanofluorophore dispersion ratio and changing edge width optimizes the fabrication process and exhibits high power conversion efficiency of-6,93%and optical efficiency of-8.57%.The LSC slab demonstrates high photostability under irradiation for prolonged hours without any dip in the emission characteristics.The Gd_(2)O_(2) S:Er,Yb nanofluorophore diffused LSC waveguide offering spectral tunability,cost-reduction,efficiency enhancement,and high concentration factor whilst being sustainable for long term use makes it a fascinating transparent solar window.

Design of a sector bowtie nano-rectenna for optical power and infrared detection

We designed a sector bowtie nanoantenna integrated with a rectifier （Au-TiOx-Ti diode） for collect- ing infrared energy. The optical performance of the metallic bowtie nanoantenna was numerically investigated at infrared frequencies （5-30 μm） using three-dimensional frequency-domain electro- magnetic field calculation software based on the finite element method. The simulation results indi- cate that the resonance wavelength and local field enhancement are greatly affected by the shape and size of the bowtie nanoantenna, as well as the relative permittivity and conductivity of the dielectric layer. The output current of the rectified nano-rectenna is substantially at nanoampere magnitude with an electric field intensity of 1 V/m. Moreover, the power conversion efficiency for devices with three different substrates illustrates that a substrate with a larger refractive index yields a higher efficiency and longer infrared response wavelength. Consequently, the optimized structure can pro- vide theoretical support for the design of novel optical rectennas and fabrication of optoelectronic devices.