High performance wide bandgap perovskite solar cell with low V_(OC) deficit less than 0.4 V

Wide bandgap perovskite solar cells(PSCs)have attracted significant attention because they can be applied to the top cells of tandem solar cells.However,high open-circuit voltage(V_(OC))deficit(>0.4 V)result from poor crystallization and high non-radiative recombination losses become a serious limitation in the pursuit of high performance.Here,the relevance between different Pbl_(2)proportions and performance parameters are revealed through analysis of surface morphology,residual stress,and photostability.The increase of Pbl_(2)proportion promotes crystal growth and reduces the work function of the perovskite film surface and promotes the energy level alignment with the carrier transport layer,which decreased the V_(OC)deficit.However,residual PbI_(2)exacerbated the stress level of perovskite film,and the resulting lattice disorder deteriorated the photostability of the device.Ultimately,after the synergistic passivation of residual PbI_(2)and PEAI,the V_(OC)achieves 1.266 V and V_(OC)deficit is less than 0.4 V,the record value in wide bandgap PSCs.

Nonlinear Multimodal Interference as Ultrafast Photonic Device for Dual-Wavelength Domain-Wall Dark Pulse Generation

In comparison to bright pulses, better stability that is not susceptible to loss makes dark pulses accessible for applications in such fields as signal processing, optics sensing, and quantum communication. Here we investigate the dual-wavelength domain-wall dark pulse generation in a graded-index multimode fiber(GIMF) based anomalous dispersion single-mode fiber(SMF) laser. By optimizing intra-cavity nonlinearity and pulse polarization, the mode-locked states can evolve each other between bright pulses, dark pulses, and bright-dark pulse pairs. The evolution mechanism among them may be relevant to the coherent mode superposition, spectral filtering, and mode selection in SMF-GIMF-SMF hybrid-fiber modulation devices that affect the pulse formation and evolution in temporal, frequency, and space domains. These results provide a valuable reference for promoting further development of nonlinear optics and ultrafast optics, in which ultrafast photonic devices, with low cost, simple manufacture as well as wide adaptability, as novel pulsed generation technique, play a vital role.

Preparation and characterization of Cd_(1-x)Zn_xS buffer layers for thin film solar cells

Cd1_xZnxS （x = 0, 0.1, 0.2, 0.3, 1.0） thin films have been grown successfully on soda-lime glass substrates by chemical bath deposition technique as a very promising buffer layer material for optoelectronic device applications. The composition, structural properties, surface morphol- ogy, and optical properties of Cd~_xZnxS thin films were characterized by energy dispersive analysis of X-ray tech- nique （EDAX）, X-ray diffraction （XRD）, scanning electron microscopy （SEM）, and UV-Vis spectrophotometer tech- niques, respectively. The annealed films were observed to possess the deficient sulfur composition. The results of XRD show that the Cdl_xZnxS （x = 0. l） thin film annealed at 450 ~C forms hexagonal （wurtzite） structure with lattice parameters a = 0.408814 nm, c ： 0.666059 nm, and its average grain size is 24.9902 nm. The diffraction peaks become strong with the increasing annealing temperatures. The surface of Cdl_~ZnxS （x = 0.1） thin film annealed at 450 ~C is uninterrupted and homogenous as compared to other temperatures. From optical properties, it is observed that the presence of small amount of Zn results in marked changes in the optical band gap of CdS. The band gaps of the Cdl_xZnxS thin films vary from 2.42 to 3.51 eV as composition varies from x = 0.0 to 1.0.

Preparation of CuInSe_2 films by ultrasonic electrodeposition-selenization and the improvement of their surface morphology

The CulnSe2 compound was prepared by selenization of Cu-In precursor, which was ultrasonic electrodeposited at constant current. CulnSe2 films were compacted to improve surface morphology. The films were characterized by X-ray diffractometry （XRD）, scanning electron microscopy （SEM）, and energy dispersive spectroscopy （EDS）. It is indicated that ideal stoichiometrie CulnSe2 films can be obtained by the selenization of Cu-In precursor deposited at a current density of 20 mA/cm^2. Single-phase CulnSe2 is formed in the selenization proeess, and it exhibits preferred orientation along the （112） plane. The CulnSe2 films with smooth surface can be obtained under the pressure of 500 MPa at 60℃.

Phonon-assisted intersubband transitions in wurtzite GaN/In_x Ga_(1-x) N quantum wells

A detailed numerical calculation on the phonon-assisted intersubband transition rates of electrons in wurtzite CaN/InxGal-xN quantum wells is presented. The quantum-confined Stark effect, induced by the built-in electric field, and the ternary mixed crystal effect are considered. The electron states are obtained by iteratively solving the coupled SchrSdinger and Poisson equations. The dispersion properties of each type of phonon modes are considered in the derivation of Fermi＇s golden rule to evaluate the transition rates. It is indicated that the interface and half- space phonon scattering play an important role in the process of 1 2 radiative transition. The transition rate is also greatly reduced by the built-in electric field. This work can be helpful for the structural design and simulation of new semiconductor lasers.

Preparation and performance of Pr-doped Ba_(0.5)Sr_(0.5)Co_(0.8)Fe_(0.2)O_(3-δ) cathode for IT-SOFCs

（Ba0.5Sr0.5）1-xPrxCo0.8Fe0.2O3-δ（BSPCFx;x=0.00-0.30） oxides were synthesized by a sol-gel thermolysis process using combination of PVA and urea,and were also investigated as cathode material for intermediate temperature solid oxide fuel cells（IT-SOFCs）.X-ray diffraction（XRD） results showed that all the samples formed a single phase cubic pervoskite-type structure after being calcined at 950 oC for 5 h and the lattice constant decreased with the Pr content increasing.The electrical conductivity of Ba0.5Sr0.5Co0.8Fe0.2O3-δ（BSCF） was greatly enhanced by Pr-doping.The thermal expansion coefficient（TEC） of BSPCFx was increased with the content of Pr increasing,and all the thermal expansion curves had an inflection at about 250-400 oC due to the thermal-induced lattice oxygen loss and the reaction of Co and Fe ion.Ac impedance analysis indicated that BSPCFx possessed better electrochemical performance.The polarization resistance of the sample with x=0.2 was only ～0.948 Ω cm2 at 500 oC,significantly lower than that of BSCF（～2.488 Ω cm2）.

Effects of Zn, Zn-Al and Zn-P Additions on the Tensile Properties of Sn-Bi Solder

Effects of Zn, Zn-Al and Zn-P additions on melting points, microstructures, tensile properties, and oxidation behaviors of Sn-40 Bi lead-free solder were investigated. The experimental results show that the addition of these three types of elements can refine the microstructures and improve the ultimate tensile strength（UTS） of solder alloys. The fractographic analysis illustrates that ductile fracture is the dominant failure mode in tensile tests of Sn-40Bi-2Zn（SBZ）and Sn-40Bi-2Zn-0.005Al（SBZA） specimens, while brittle fracture is the controlled manner in Sn-40Bi-2Zn-0.005P（SBZP） and Sn-58 Bi solders. XPS analysis indicates that trace amounts of both Al and P additives in solder can improve the antioxidant capacity, whereas only the additive of Al in solder can reduce the thickness of oxidation film.

Preparation and characterization of Cu2ZnSn(S,Se)4 film by drop-coating of Cu2ZnSnS4 nanoink

In this work,a simple and facile one-pot oleylamine solvothermal synthetic method was developed to synthesize Cu2ZnSnS4（CZTS） nanocrystals.And the Cu2ZnSn（S,Se）4（CZTSSe） thin films were prepared by selenizing CZTS nanocrystals.The obtained CZTS nanocrystals and CZTSSe films were studied using X-ray diffraction（XRD）,transmission electron microscopy（TEM）,scanning electron microscopy（SEM）,energy-dispersive X-ray spectroscopy（EDX）,and ultraviolet–visible spectrophotometer（UV–Vis）.TEM results show that the sphere–like CZTS nanoparticles with diameter between 12 and 35 nm are polydispersed.XRD studies indicate that the prepared CZTS nanocrystals form kesterite crystal structure,and the CZTSSe films with kesterite crystal structure are also obtained at the annealing temperatures of 500 and550 °C.In particular after annealing at 500 °C for 20 min,the CZTSSe film exhibits a smooth,uniform,crack-free,and large-grained topography and possesses Cu-poor and Sn-rich composition.Moreover,it shows strong optical absorption from visible to near-infrared（IR） region,and its optical band gap（Eg） is found to be about 1.44 e V.

Highly transmitted silver nanowires-SWCNTs conductive flexible film by nested density structure and aluminum-doped zinc oxide capping layer for flexible amorphous silicon solar cells

Indium tin oxide(ITO)is widely used in transparent conductive films(TCFs);however,several disadvan-tages,such as high cost and toxicity of indium,limit its applications.Therefore,it is necessary to develop other materials that can replace ITO.Silver nanowires or single walled carbon nanotubes(SWCNTs)have attracted considerable interest owing to their unique electrical,optical,and thermal stabilities,and thus,they are ideal for transparent electrodes for flexible or stretchable devices.In this study,we develop a novel architecture of composite TCFs on a polyethylene naphthalate(PEN)flexible substrate.Herein,the silver nanowires-SWCNTs films with nested density structure were fabricated through ultrasonic spraying technology by varying the spraying width.For achieving enhanced transmittance,we combined the larger irregular grids and holes with fewer nanowires stacked in the longitudinal direction,more optical chan-nels,and good carrier transport.Thereafter,aluminum-doped zinc oxide(AZO)was used as capping to the structure for enhancing the optical properties of the TCFs.The silver nanowires-SWCNTs/AZO(ASA)bilayer was obtained in the optimized architecture,which showed superior optoelectronic performance to that shown by commercial ITO with a high optical transmittance of 92%at the wavelength of 550 nm and low sheet resistance of 17/sq.In the specially structured conductive film,the significant improvement in the transmittance and uniformity of the sheet resistance was attributed to the effective nanowire junc-tion contact compared to that in ordinary structure of silver nanowires,which reduced the mean density of small clusters of nanowires.Compared with the silver nanowires-SWCNTs films,the ASA bilayer film exhibited excellent resistance to boiling,mechanical bending(10,000 cycles),and CO_(2)plasma.Moreover,the sheet resistance of ASA changed slightly after the tape tests,thereby illustrating a strong adhesion to the PEN substrate after the enclosure of AZO.Meanwhile,the AZO capping layer can enhance the op-tical transmittance between 600 and 1500 nm.In addition,the amorphous silicon photovoltaic devices with flexible ASA TCFs exhibited a power conversion efficiency(PCE)of 8.67%.After bending for 3000 times,the PCE was decreased to 8.20%,thereby demonstrating the potential of developed films to replace traditional ITO.