X-ray photoelectron spectroscopic studies of black silicon for solar cell

The black silicon has been produced by plasma immersion ion implantation (PIII) process. The microstructure and optical reflectance are characterized by field emission scanning electron microscope and spectrophotometer. Results show that the black silicon appears porous or needle-like microstructure with the average reflectance of 4.87% and 2.12%, respectively. The surface state is investigated by X-ray photoelectron spectroscopy (XPS) technique. The surface of the black silicon is composed of silicon, carbon, oxygen and fluorine element. The formation of Si_xO_yF_z in the surface of black silicon can be proved clearly by the O 1s, F 1s and Si 2p XPS spectra. The formation mechanism of the black silicon produced by PIII process can be obtained from XPS results. The porous or needle-like structure of the black silicon will be formed under the competition of SF_x⁺ (x ≤ 5) and F⁺ ions etching effect, Si_xO_yF_z passivation and ion bombardment.     

Reduction of the phosphorus contamination for plasma deposition of p-i-n microcrystalline silicon solar cells in a single chamber

This paper investigates several pretreatment techniques used to reduce the phosphorus contamination between solar cells. They include hydrogen plasma pretreatment, deposition of a p-type doped layer, i-a-Si:H or μc-Si:H covering layer between solar cells. Their effectiveness for the pretreatment is evaluated by means of phosphorus concentration in films, the dark conductivity of p-layer properties and cell performance.     

A new kind of superimposing morphology for enhancing the light scattering in thin film silicon solar cells:Combining random and periodic structure

In this article, a new type of superimposing morphology comprised of a periodic nanostructure and a random structure is proposed for the first time to enhance the light scattering in silicon-based thin film solar cells. According to the framework of the Reyleigh-Sommerfeld diffraction algorithm and the experimental results of random morphologies, we analyze the light-scattering properties of four superimposing morphologies and compare them with the individual morphologies in detail. The results indicate that the superimposing morphology can offer a better light trapping capacity, owing to the coexistence of the random scattering mechanism and the periodic scattering mechanism. Its scattering property will be dominated by the individual nanostructures whose geometrical features play the leading role.     

Characteristics of dual-frequency capacitively coupled SF_6/O_2 plasma and plasma texturing of multi-crystalline silicon

Due to it being environmentally friendly, much attention has been paid to the dry plasma texturing technique serving as an alternative candidate for multicrystalline silicon(mc-Si) surface texturing. In this paper, capacitively coupled plasma(CCP) driven by a dual frequency(DF) of 40.68 MHz and 13.56 MHz is first used for plasma texturing of mc-Si with SF6/O2gas mixture. Using a hairpin resonant probe and optical emission techniques, DF-CCP characteristics and their influence on mc-silicon surface plasma texturing are investigated at different flow rate ratios, pressures, and radio-frequency(RF)input powers. Experimental results show that suitable plasma texturing of mc-silicon occurs only in a narrow range of plasma parameters, where electron density n9e must be larger than 6.3 × 10cm-3and the spectral intensity ratio of the F atom to that of the O atom([F]/[O]) in the plasma must be between 0.8 and 0.3. Out of this range, no cone-like structure is formed on the mc-silicon surface. In our experiments, the lowest reflectance of about 7.3% for mc-silicon surface texturing is obtained at an [F]/[O] of 0.5 and ne of 6.9 × 109cm-3.     

Conformal Invariance and Noether Conserved Quantities of First-Order Lagrange Systems

In this paper the conformal invariance by infinitesimal transformations of first-order Lagrange systems is discussed in detail. The necessary and sumeient conditions of conformal invariance by the action of infinitesimal transformations being Lie symmetry simultaneously are given. Then we get the conserved quantities of conformal invariance by the infinitesimal transformations. Finally an example is given to illustrate the application of the results.     

The mechanism of hydrogen plasma passivation for poly-crystalline silicon thin film

The mechanism of hydrogen plasma passivation for poly-crystalline silicon （poly-Si） thin films is investigated by optical emission spectroscopy （OES） combined with Hall mobility, Raman spectra, absorption coefficient spectra, and so on. It is found that different kinds of hydrogen plasma radicals are responsible for passivating different defects in polySi. The Ha with lower energy is mainly responsible for passivating the solid phase crystallization （SPC） poly-Si whose crystallization precursor is deposited by plasma-enhanced chemical vapor deposition （PECVD）. The H＊ with higher energy may passivate the defects related to teh Ni impurity around the grain boundaries more effectively. In addition, Hβ and H7 with the highest energy are required to passivate intra-grain defects in the poly-Si crystallized by SPC but whose precursor is deposited bv low pressure chemical vapor deposition（LPCVD）     

AlOx prepared by atomic layer deposition for high efficiency-type crystalline silicon solar cell

The influence of atomic layer deposition parameters on the negative charge density in AlOx film is investigated by the corona-charge measurement. Results show that the charge density can reach up to -1.56×10^12 cm%-2 when the thickness of the film is 2.4 nm. The influence of charge density on cell conversion efficiency is further simulated using solar cell analyzing software （PC1D）. With AlOx passivating the rear surface of the silicon, the cell efficiency of 20.66% can be obtained.     

Amorphous/crystalline silicon heterojunction solar cells with black silicon texture

Excellent passivation of black silicon surfaces by thin amorphous silicon layers deposited with plasma enhanced chemical vapor deposition is demonstrated. Minority charge carrier lifetimes of 1.3 milliseconds, enabling an implied open‐circuit voltage of 714 mV, were achieved. The influence of amorphous silicon parasitic epitaxial growth and thickness, as well as of the texture depth is investigated. Furthermore, quantum efficiency gains for wavelengths above 600 nm, as compared to random textured solar cells, are demonstrated in 17.2% efficient amorphous–crystalline silicon heterojunction solar cells with black silicon texture. (© 2014 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim)     

Charge state distribution analysis of AI and Pb ions from the laser ion source at IMP

A prototype laser ion source that could demonstrate the possibility of producing intense pulsed high charge state ion beams has been established with a commercial Nd：YAG laser （E =3 J, 1064 rim, ~ 10 ns） to produce laser plasma for the research of Laser Ion Source （LIS）. At the laser ion source test bench, high purity （99.998%） aluminum and lead targets have been tested for laser plasma experiment. An Electrostatic Ion Analyzer （EIA） and Electron Multiply Tube （EMT） detector were used to analyze the charge state and energy distribution of the ions produced by the laser ion source. The maximum charge states of A112＋ and Pb7＋ were achieved. The results will be presented and discussed in this paper.     

Boundary States and Correlation Functions of Tricritical Ising Model from Coulomb-Gas Formalism

We consider the minimal conformaJ model describing the tricritical Ising model on the disk and on the upper half plane. Using the coulomb-gas formalism we determine its consistents boundary states as well as its one-point and two-point correlation functions.     

Dye-sensitized solar cells: Atomic scale investigation of interface structure and dynamics

Recent progress in dye-sensitized solar cells(DSC) research is reviewed, focusing on atomic-scale investigations of the interface electronic structures and dynamical processes, including the structure of dye adsorption onto TiO2, ultrafast electron injection, hot-electron injection, multiple-exciton generation, and electron–hole recombination. Advanced experimental techniques and theoretical approaches are briefly summarized, and then progressive achievements in photovoltaic device optimization based on insights from atomic scale investigations are introduced. Finally, some challenges and opportunities for further improvement of dye solar cells are presented.     

Effect of annealing on performance of PEDOT:PSS/n-GaN Schottky solar cells

We develop a heterojunction-based Schottky solar cell consisting of n-type GaN and PEDOT：PSS and also investigate the effect of annealing on the performance of the solar cell. The results show that the open circuit voltage （Voc） increases from 0.54 V to 0.56 V, 0.71 V and 0.82 eV while decreases to 0.69 eV after annealing at 100 ℃, 130 ℃, 160 ℃, and 200 ℃, respectively, which can be ascribed to the change of barrier height of PEDOT：PSS/GaN Schottky contact induced by variation of the work function of the PEDOT：PSS. Furthermore, the conductivity and surface roughness measurements of the PEDOT：PSS indicate that annealing can increase the grain size and improve the connectivity between PEDOT and PSS particles, and cause thermal degradation at the same time, which leads to the rise in short-circuit current density （ISC） up to 160 ℃ and the dropoff in ISC after annealing at 200 ℃.     

On Thermodynamical Relation Between Rotating Charged BTZ Black Holes and Effective String Theory

In this paper we study the first law of thermodynamics for the （2＋1）-dimensional rotating charged BTZ black hole considering a pair of thermodynamical systems constructed with the two horizons of this solution. We show that these two systems are similar to the right and left movers of string theory and that the temperature associated with the black hole is the harmonic mean of the temperatures associated with these two systems.     

Conformal Invariance and a New Type of Conserved Quantities of Mechanical Systems with Variable Mass in Phase Space

Conformal invariance and a new type of conserved quantities of mechanical systems with variable mass in phase space are studied. Firstly, the definition and determining equation of conformal invariance are presented. The relationship between the conformal invariance and the Lie symmetry is given, and the necessary and sufficient condition that the conformal invarianee would be the Lie symmetry under the infinitesimal transformations is provided. Secondly, a new type of conserved quantities of the conformal invariance are obtained by using the Lie symmetry of the system. Lastly, an example is given to illustrate the application of the results.     

Nanocystalline silicon solar cells

Nanocrystalline silicon material has made rapid progress in the last several years and at present it can be defined as real device quality as a photoactive layer for solar cells. A number of innovative ideas, such as the deposition at the crystalline to amorphous transition, at high pressure depletion condition, by taming of the ion energy, by grading of the material growth, at reduced unwanted dopant incorporation, have helped to reach an efficiency of 10% for single junction nanocrystalline silicon cells. In situ plasma and gas phase diagnosis have contributed to the fast optimisation of deposition process parameters. Deposition rate, open circuit voltage and light confinement are some of most critical issues that are currently pursued. Materials with a defect density as low as 10¹⁵ cm⁻³ have been made, however, they are still not good enough for n–p junctions; the device structure is still of drift type in a p–i–n or n–i–p configuration.     

MoO3/Ag/AI/ZnO intermediate layer for inverted tandem polymer solar cells

We report an MoO3/Ag/Al/ZnO intermediate layer connecting two identical bulk heterojunction subcells with a poly（3-hexylthiophene） and [6,6]-phenyl-C61-butyric acid methyl ester （P3HT and PCBM） active layer for inverted tan- dem polymer solar cells. The highly transparent intermediate layer with an optimized thickness realizes an Ohmic contact between the two subcells for effective charge extraction and recombination. A maximum power conversion efficiency of 3.76% is obtained for the tandem cell under 100 mW/cm2 illumination, which is larger than that of a single cell （3.15%）. The open-circuit voltage of the tandem cell （1.18 V） approaches double that of the single cell （0.61 V）.     

Noncommutative Singular Black Holes

In this paper, applying the method of coordinate coherent states to describe a noncommutative model of Vaidya black holes leads to an exact （t - r） dependence of solution in terms of the noncommutative parameter σ. In this setup, there Js no black hole remnant at long times.     

Covariant Anomaly and Hawking Radiation from Kerr-Newman Black Hole in Dragging Coordinates Frame

in the light of Robinson and Wilczek＇s new idea, and motivated by Banerjee and Kulkarni＇s simplified method of using only the covariant anomaly to derive Hawking radiation from a black hole, we generally extend the work to Kerr-Newman black hole in dragging coordinates frame. It is shown that the flows introduced to cancel the anomaly at the event horizon are equal to the corresponding Hawking radiation in dragging coordinates frame, which supports and extends Robinson and Wilczek＇s opinion.     

Thermal Phase in Bubbling Geometries

We use matrix model to study thermal phase in bubbling half-BPS type liB geometries with SO（4） × SO（4） symmetry. Near the horizon limit, we find that thermal vacua of bubbling geometries have disjoint parts, and each part is one kind of phase of the thermal system. We connect the thermal dynamics of bubbling geometries with one-dimensional fermions thermal system. Finally, we try to give a new possible way to resolve information loss puzzle.