Defect chemistry engineering of Ga-doped garnet electrolyte with high stability for solid-state lithium metal batteries

Ga-doped Li_(7)La_(3)Zr_(2)O_(12)(Ga-LLZO)has long been considered as a promising garnet-type electrolyte candidate for all-solid-state lithium metal batteries(ASSLBs)due to its high room temperature ionic conductivity.However,the typical synthesis of Ga-LLZO is usually accompanied by the formation of undesired LiGaO_(2) impurity phase that causes severe instability of the electrolyte in contact with molten Li metal during half/full cell assembly.In this study,we show that by simply engineering the defect chemistry of Ga-LLZO,namely,the lithium deficiency level,LiGaO_(2) impurity phase is effectively inhibited in the final synthetic product.Consequently,defect chemistry engineered Ga-LLZO exhibits excellent electrochemical stability against lithium metal,while its high room temperature ionic conductivity(~1.9×10^(-3)S·cm^(-1))is well reserved.The assembled Li/Ga-LLZO/Li symmetric cell has a superior critical current density of 0.9 mA·cm^(-2),and cycles stably for 500 hours at a current density of 0.3 mA·cm^(-2).This research facilitates the potential commercial applications of high performance Ga-LLZO solid electrolytes in ASSLBs.

Electric-Field-Assisted Growth of Ga-Doped ZnO Nanorods Arrays for Dye-Sensitized Solar Cells

A photoanode with Ga-doped ZnO nanorods has been prepared on F-doped SnO2 (FTO) coated glass substrate and its application in dye-sensitized solar cells (DSSCs) has been investigated. Ga-doped ZnO nanorods have been synthesized by an electric-field-assisted wet chemical approach at 80?C. Under a direct current electric field, the nanorods predominantly grow on cathodes. The results of the X-ray photoelectron spectroscopy and photoluminescence verify that Ga dopant is successfully incorporated into the ZnO wurtzite lattice structure. Finally, employing Ga-doped ZnO nanorods with the length of ~5 μm as the photoanode of DSSCs, an overall energy conversion efficiency of 2.56% is achieved. The dramatically improved performance of Ga-doped ZnO based DSSCs compared with that of pure ZnO is due to the higher electron conductivity.

Properties of multilayer gallium and aluminum doped ZnO(GZO/AZO) transparent thin films deposited by pulsed laser deposition process

Multilayer gallium and aluminum doped ZnO （GZO/AZO） films were fabricated by alternative deposition of Ga-doped zinc oxide（GZO） and Al-doped zinc oxide（AZO） thin film by using pulsed laser deposition（PLD） process. The electrical and optical properties of these GZO/AZO thin films were investigated and compared with those of GZO and AZO thin films. The GZO/AZO （1：1） thin film deposited at 400 ~C shows the electrical resistivity of 4.18 x 10 4 ~.cm, an electron concentration of 7.5 x 1020/cm3, and carrier mobility of 25.4 cm2/（V.s）. The optical transmittances of GZO/AZO thin films are over 85%. The optical band gap energy of GZO/AZO thin films linearly decreases with increasing the AI ratio.

Crystalline Size Effects on Texture Coefficient,Electrical and Optical Properties of Sputter-deposited Ga-doped ZnO Thin Films

C-axis oriented Ga-doped ZnO(GZO) films with various thicknesses were deposited on glass substrate by radio frequency(RF) magnetron sputtering. The dependence of crystal structure,electrical,and optical properties of the GZO films on crystalline size were systematically studied. The results showed that the texture coefficient of (002) peak (TC(002)) decreases with increasing crystalline size. The Hall mobility m was reciprocal to electron effective mass and the fitted relaxation time s was 0.11±0.01 ms. With the increase of average crystalline size,the resistivity increased slightly,which is caused by the competition of (002) and(101) plane,introducing in some defects and leading to carrier density reduction. The optical band gap was in the range from 3.454 to 3.319 eV with increasing crystalline size from 26.96 to 30.88 nm,showing a negative relationship. The dependence of optical band gap (Eopg) on the crystalline size(R) can be qualitatively explained by a quantum confinement effect. The relationship between Eopg and R of GZO films suggests that tuning up optical properties for desired applications can be achieved by controlling the crystalline size.

Improved Energy Conversion Efficiency of ZnO/Polythiophene Solar Cell in Ga-Doped ZnO Nanorod Array Photoanode

We reported the fabrication and doping effect of Ga-doped ZnO nanorods/electropolymerized polythio-phene（e-PT） hybrid photovoltaic（h-PV） devices. Ga-Doped ZnO nanorod array photoanode devices were fabricatedvia hydrothermally growing nanorods on sol-gel spin-coating ZnO seed layer, and then the nanorod array was im-mersed into a thiophene solution to yield a thin polythiophene film by electrochemically polymerization. Afterwards,a thin layer of A1 was deposited on the surface of polythiophene to make an electrode for photovoltaic measurement.The ZnO nanorods with different Ga-doping contents were characterized by means of X-ray diffraction（XRD）, scan-ning electron micrograph（SEM） and X-ray photoelectron spectroscopy（XPS）. Photovoltaic J-V characterization wasperformed on the e-PT/ZnO bilayer and bulk heterojunction（BHJ） devices. Though the unsubstituted polythiophene isnot an ideal polymer material for solar cells with high power conversion efficiency, it is a sound model for the studyon the effect of dopant in hybrid materials. The results indicate that doping Ga can substantially improve the powerconversion efficiency of the ZnO-polythiophene solar cell.

A Ga-doped ZnO transparent conduct layer for GaN-based LEDs

An 8μm thick Ga-doped ZnO（GZO） film grown by metal-source vapor phase epitaxy was deposited on a GaN-based light-emitting diode（LED） to substitute for the conventional ITO as a transparent conduct layer（TCL）. Electroluminescence spectra exhibited that the intensity value of LED emission with a GZO TCL is markedly improved by 23.6%as compared to an LED with an ITO TCL at 20 mA.In addition,the forward voltage of the LED with a GZO TCL at 20 mA is higher than that of the conventional LED.To investigate the reason for the increase of the forward voltage,X-ray photoelectron spectroscopy was performed to analyze the interface properties of the GZO/p-GaN heterojunction.The large valence band offset（2.24±0.21 eV） resulting from the formation of Ga_2O_3 in the GZO/p-GaN interface was attributed to the increase of the forward voltage.

Figure of Merit Enhancement of Surface Plasmon Resonance Biosensor Using Ga-Doped Zinc Oxide in Near Infrared Range

This work presents a surface plasmon resonance biosensor for the figure of merit enhancement by using Ga-doped zinc oxide(GZO),i.e.,nanostructured transparent conducting oxide as plasmonic material in place of metal at the telecommunication wavelength.Two-dimentional graphene is used here as a biorecognition element(BRE)layer for stable and robust adsorption of biomolecules.This is possible due to stronger van der Waals forces between graphene’s hexagonal cells and carbon-like ring arrangement present in biomolecules.The proposed sensor shows improved biosensing due to fascinating electronic,optical,physical,and chemical properties of graphene.This work analyses the sensitivity,detection accuracy,and figure of merit for the GZO/graphene SPR sensor on using the dielectric layer in between the prism and GZO.The highest figure of merit of 366.7 RIU^(−1) is achieved for the proposed SPR biosensor on using the nanostructured GZO at the 3000 nm dielectric thickness.The proposed SPR biosensor can be used practically for sensing of larger size biomolecules with due availability of advanced techniques for the fabrication of the nanostructured GZO and graphene.

GaZn-VZn acceptor complex defect in Ga-doped ZnO

Gallium （Ga）-doped ZnO is regarded as a promising plasmonic material with a wide range of applications in plasmonics. In this study, zinc self-diffusion experiments are adopted to disclose the nature of the dominant compensating defect in Ga-doped ZnO isotopic heterostructures. The （GaZn-VZ.）- complex defect, instead of the isolated VZn^2-, is identified as the predominant compensating acceptor center responsible for the low donor doping efficiency. The comparative diffusion experiments operated by the secondary ion mass spectrometry reveal a -0.78 eV binding energy of this complex defect, which well matches the electrical activation energy derived from the temperature-dependent Hall effect measurements （-（0.82±0.02） eV）. These findings contribute to an essential understanding of the （GaZn-VZn）- complex defect and the potential engineering routes of heavily Ga-doped ZnO.