Nuclear fuel claddings are the first barrier against fission products in a primary circuit. Eddy current testing (ECT) is a commonly used nondestructive testing technique for measuring the thickness of chromium and oxide layers on claddings. Because of the lack of an analytical model for ECT probes above multilayer pipes, the design and optimization of the probe have not been reported. In this article, an analytical model for coils placed outside multilayer pipes involving arbitrary nonconductive and conductive layers is built based on second-order vector potential (SOVP). A model of nuclear fuel claddings is built, and the influence of probe parameters on signals is analyzed. According to the results, a design flowchart for the ECT probe is provided by considering resonance frequency and quality factors. Comparisons among the experiment, finite element model, and analytical model indicate that the built analytical model is validated and efficient. In addition, the performance of the new probe is better and more sensitive than that of the old probe; therefore, the proposed design flowchart is effective.

Inverted perovskite solar cells (PSCs) attract researchers' attention for their potential application due to the low-temperature fabrication, negligible hysteresis and compatibility with multi-junction cells. However, the low-temperature fabricated perovskite films containing excessive undesired defects are not benefit for improving the performance of the inverted PSCs. In this work, we used a simple and effective passivation strategy that Poly(ethylene oxide) (PEO) polymer as an antisolvent additive to modify the perovskite films. The experiments and simulations have shown that the PEO polymer can effectively passivate the interface defects of the perovskite films. The defect passivation by PEO polymers suppressed non-radiative recombination, resulting in an increase in power conversion efficiency (PCE) of the inverted devices from 16.07% to 19.35%. In addition, the PCE of unencapsulated PSCs after PEO treatment maintains 97% of its original stored in a nitrogen atmosphere for 1000 h.

Despite the widespread use of metal oxides as electron selective contacts (ESCs) in dopant-free passivating contact crystalline silicon (c-Si) solar cells, their stability and performance improvements still encounter bottlenecks. Herein, we investigated the potential of zinc sulfide (ZnS) as ESC for n-type c-Si (n-Si) solar cells. The performance of the ZnS-based dopant-free n-Si solar cells has been optimized by deploying the low-work-function Mg/Ag stack electrode and a SiOx passivation interlayer with forming gas annealing (FGA) treatment. An efficiency of 20.03% has been achieved for n-Si solar cells with SiOx(FGA)/ZnS/Mg/Ag contact, which is so far the highest efficiency reported for ZnS-based c-Si solar cells. Moreover, the device maintained ≥98% of its initial efficiency after being stored in the air for 30 days, indicating the promise of long-term deployment. Our work highlights the great potential of using metal sulfides as high-performance and stable passivating contacts in dopant-free c-Si solar cells.

Boron laser doping selective emitter (LDSE) has attracted much attention in the current mass-production of n-type tunnel oxide passivated contact (TOPCon) crystalline silicon (c-Si) solar cells. However, boron LDSE technology is limited by the low boron concentration of borosilicate glass (BSG) during boron diffusion, as well as the inefficient doping and laser-induced damage. Here, a thinner BSG layer with high boron concentration has been achieved by adjusting the boron diffusion conditions, which overcomes the insufficient diffusion dynamics caused by the low diffusion and segregation coefficients of boron atoms to improve the surface passivation and promote the laser doping. We have demonstrated that high-temperature annealing has a better repair on laser-induced damage compared with wet etching back due to the surface tension and internal stress after solidification of the silicon molten pool. More importantly, the synergistic effect of high-temperature annealing and wet etching back results in much better results, together with good compatibility with the subsequent cell production processes without increasing production costs. The influence of front emitter parameters has been further quantified theoretically to provide a meaningful guidance for the development of TOPCon c-Si solar cells with front LDSE.

Optical simulations allow the evaluation of the absorption, reflection, and transmission of each functional layer of solar cells and, therefore, are of great importance for the design of high-efficiency crystalline silicon (c-Si) solar cells. Here, a multi-scale simulation method (MSM) based on ray and wave optics is proposed to investigate the optical characteristics of c-Si solar cells. The ray and wave optical methods are first independently employed on inverted pyramid glass sheets, where the latter one can describe the size-dependent interfacial scattering characteristics more accurately. Then the optical properties of a c-Si solar cell with a tunnel oxide passivated carrier-selective contact configuration are studied by employing the MSM, where scattering at the interfaces is acquired by a finite-difference time-domain method (wave optics). Since the MSM can accurately simulate optical modes such as the Rayleigh anomaly, Bloch mode, and Mie resonances, the reflection and transmission spectra of the whole device are in good agreement with the measured data. The proposed MSM has proven to be accurate for structures with functional thin films, which can be extended to hybrid tandem devices with top-level cells consisting of stacks of layers with similar dimensions.

The investigation aims to reveal and confirm the phosphorus (P)-oxygen (O) bonds formed in the poly-Si (n+) film of the TOPCon device, which is beneficial for reducing the resistivity and the potential barriers of grain boundaries (GBs) due to further passivation of GBs within the film. To overcome the difficulty of gaining the chemical components in the interface and bulk of the n-Si/SiOx/poly-Si (n+) materials, we undertake X-ray photoelectron spectroscopy (XPS) with the depth profile by means of argon ion milling, in which the collision damage of ion with target surface has been neglected because of an effective detectable depth and longer mean escape depth of the optoelectron in the ionized state in the sampling point of the subsurface. High -resolution transmission electron microscopy (HR-TEM) has been employed to check the atomic lattice morphology of the multi-layer stacks for further distinguishing the crystallographic plane orientation of crystallites and ultrathin SiOx layer feature distribution in the interfacial region and bulk of SiOx/poly-Si (n+) films. The results of XPS-P 2p fitting peaks at 133.4 and 136.2 eV and -O 1s satellite peak at 535.3 eV, respectively, manifesting that the P-O bonds or derivatives (POx) may be present in the poly-Si (n+) film and localized in the GBs, through the heavily P dopants that induce tensile stress within crystallites and compress stress in GBs. The conclusion has been supported by the variation of thermodynamic functions, such as molar enthalpy, reaction entropy, Gibbs energy, and formation energy of silicon and phosphorus oxides, at the temperatures of 298 and 1173 K in terms of the minimum principle of energy.

Dopant-free carrier-selective contacts based on metal compounds have attracted considerable attention for high-efficiency crystalline silicon solar cells. In this work, the feasibility of using molybdenum oxynitride (MoOxNy) as an electron-selective contact layer in n-type crystalline silicon (n-Si) solar cells has been demonstrated. With the increase in the N2:Ar ratio during the sputtering process, the work function of a MoOxNy film decreases from 4.57 to 4.26 eV, which is advantageous for the MoOxNy film to be an electron transport layer. An efficiency of 18.0% has been achieved in n-Si based solar cells using a full-area MoOxNy contact for electron extraction, featuring a high fill factor of 84.6%.

n-type silicon (Si) technologies played a major role in the early age of photovoltaics (PV). Indeed, the Bell Laboratories prepared the first practical solar cells from n-type crystalline Si (c-Si) wafers (Figure 3.1) [1-3]. Therefore, the domination of p-type technologies over the last decades for the production of commercial solar cells could appear as a paradox. This is essentially explained by historical reasons. Fifty years ago, the dominant market for c-Si solar cells was space power applications. In space, solar components are affected by radiation damages (electrons, protons). Interestingly, this degradation is significantly reduced by using p-type cells instead of n-type devices [4]. Thus, the solar cell developments for space applications focused on p-type wafers. When the first commercial productions for terrestrial applications were launched, they took benefit of these early developments for space missions and were therefore naturally based on p-type devices. Then, with the rapid growth of PV, p-type solar cells were the main recipients of the industrially oriented innovations and eventually maintained their domination over the PV market.

We investigate the voltage-controlled magnetism effect of HfZrO/CoFeB hybrid film and a Hall device with perpendicular magnetic anisotropy. The magnetization versus magnetic field experiments and anomalous Hall experiments before and after applying voltage are performed. The results exhibit that the coercive field of samples remain unchanged while the saturation magnetization shows a permanent increase (more than 60%), which is regardless of the direction of applied voltage. Different from conventional voltage-controlled magnetic anisotropy, in our work, only the saturation magnetization is enhanced by the applied voltage without trading off other magnetic parameters of CoFeB. Thus, such a finding proposes a more efficient voltage-controlled method to achieve a magnetic memory device with high thermal stability, high tunnel magnetoresistance and low switching current for magneto-resistive random-access memory under scaling beyond 2X nm.

At present, conventional micron-pyramid texture is imperfect for further reducing optical reflection loss and improving photoelectric conversion efficiency (PCE) of tunnel oxide passivating contact (TOPCon) solar cells. Herein, reactive ion etching technique is used to fabricate nanopores on top of pre-formed micron-pyramid silicon surface, called NPP structure. The equivalent medium layer with graded refractive index appeared on NPP textures makes the absorption of almost all incident light independent of the wavelength and angle. However, serious Auger recombination and surface recombination associated with NPP structure is detrimental to emitter passivation, usually counteracting the photocurrent gain. To identify an appropriate balance of light-trapping and surface passivation, we investigate the impact of different radio-frequency power (PRF) on the optical and electrical properties of TOPCon solar cells and discusses the underlying structural causes behind these observed improvements. Finally, we demonstrate NPP TOPCon solar cells with an average short-circuit current density of 41.44 mA/cm(2) and an average PCE of 23.55% at the PRF of 600 W. Besides, the external quantum efficiency results under various incident angles from 0 degrees to 70 degrees exhibited excellent wide-angle spectral absorption capability, which is significant for solar cells working in an outdoor environment.

Optical loss is a significant factor restricting the conversion efficiency of conventional bifacial tunnel oxide passivating contact (TOPCon) solar cells. Black silicon structure is commonly used to enhance the photo generated current density (J(ph)) of crystalline solar cells due to its excellent light-trapping capability. However, the photogenerated current gain is cancelled by the increased emitter recombination current originated from the black silicon structure with a high enhanced surface area ratio. In this work, we used a buffered oxide etching solution to modify the surface morphology of nanopore/micron-pyramid composite (NPP) structure silicon. Further, we studied the effects of NPP structures with different enhanced surface area ratio on front-side reflection, boron atom doping, emitter passivation, and cell performance. By identifying the appropriate surface modification processing, we fabricated the large-scale (158.75 mm x 158.75 mm) bifacial TOPCon solar cells using industrial equipment and processes with an average short-circuit current density of 41.12 mA/cm(2) and average conversion efficiency of 23.08%. Through adequately widening nanostructure size and depositing high-quality Al2O3/SiNx stacked passivation films on NPP structure surface, we achieved lower carrier recombination while maintaining high J(ph).

In this work we investigated the optical and electrical performance of p-type epitaxial layers as the rear emitter of bifacial n-type PERT solar cells. In the first part of this paper, the surface morphology of epitaxial layers grown on textured surfaces is studied. Because of the epitaxial growth, a pyramids-rounding effect is observed as a result of {311} and {911} facet propagation. The growth pattern was quantified and modelled. In the second part of this paper, the optical performance of semi-device test structures is evaluated. The trend of the optical results in bifacial solar cell structures indicates that a final pyramid angle at the rear side around 20 degrees gives the maximum light absorption in the wafer substrate. In this work we demonstrate that the epitaxial growth of the emitter on the textured rear side of these devices can already give a pyramid angle of 25 degrees without having to introduce any additional polishing steps to modify the morphology of the textured surface. In the last part of this paper, we present the electrical results for semi-device structures created to quantify the recombination losses in the passivated and metallized regions of those p-type epitaxial emitters. These results indicate that by introducing a rear epitaxial emitter in the bifacial n-type PERT cell structure, we can increase the implied V-OC up to 17 mV compared to a diffused emitter with the same sheet resistance.

In this work, we improved the performance of the MWT-PERT solar cells focusing on increasing their Voc by combining the MWT concept with n-PERT technology. The impact of different post-laser treatments on the via surface morphology and the via passivation was investigated. KOH texturing can partially remove the laser damage in the via and reduce the via SRV to 1000 cm/s. With optimized post-laser treatment and via passivation, an average Voc of 685mV was achieved for our large-area n-type MWT-PERT cells. Front Ni/Cu plating and rear Ag and Al screen-printing were used for the metallisation, the compatibility of this hybrid metallisation scheme was studied. Using industrial solder-through interconnection technology, the cell was integrated in a laminate reaching a one-cell module efficiency at 20%. The reliability of the one-cell modules was preliminarily investigated in an extended reliability test.

This work focuses on analytical modelling as an alternative to numerical simulations for determining via-related recombination losses in MWT silicon solar cells. Two new analytical models are presented in this framework. The first model deals with calculation of the local via recombination velocity S-via from photoconductance lifetime measurements. The second model relates S-via to loss in V-OC by solving the diffusion equation in two-dimensions. From short-loop tests, we show that these analytical models are valid over a wide range of via densities. The results also show that alkaline etching treatment after the laser via drilling step reduces S-via by an order of magnitude and thus allows for good via passivation. We then make use of these models for estimating V-OC loss in our MWT solar cells as a result of via recombination. We find that via recombination losses can be substantial at high via densities and so by limiting the number of vias on large area cells (239 cm(2)) and with good via passivation, the V-OC loss can be limited to similar to 1 mV. This finding is in agreement with our cell integration results. (C) 2017 The Authors. Published by Elsevier Ltd.

We present large-area n-type PERT solar cells featuring a rear boron emitter passivated by a stack of ALD Al2O3 and PECVD SiOx. After illustrating the technological and fundamental advantages of such a device architecture, we show that the Al2O3/SiOx stack employed to passivate the boron emitter is unaffected by the rear metallization processes and can suppress the Shockley-Read-Hall surface recombination current to values below 2 fA/cm(2), provided that the Al2O3 thickness is larger than 7 nm. Efficiencies of 21.5% on 156-mm commercial-grade Cz-Si substrates are demonstrated in this study, when the rear Al2O3/SiOx passivation is applied in combination with a homogeneous front-surface field (FSF). The passivation stack developed herein can sustain cell efficiencies in excess of 22% and V-oc above 685 mV when a selective FSF is implemented, despite the absence of passivated contacts. Finally, we demonstrate that such cells do not suffer from light-induced degradation.

n-type silicon wafer solar cells are receiving increasing attention for industrial application in recent years, such as the n-type rear-junction Passivated Emitter Rear Totally-diffused (PERT) solar cells. One of the main challenges in fabricating the n-PERT solar cells is the opening of the rear dielectric for localized contacts. In this work laser ablation is applied to locally ablate the rear dielectric. We investigate the laser damage to the emitter at the laser-ablated regions using the emitter saturation current density, J(0e,laser),, laser, extracted by two approaches. J(0e), laser is observed to be injection dependent due to high J(02) recombination caused by laser damage to the space charge region. By using the optimized laser ablation parameters, n-PERT solar cells with an efficiency of up to 21.0% are realized. Copyright (C) 2015 John Wiley & Sons, Ltd.

Water-dispersed organic nanoparticles (NPs) were prepared from a conjugated molecule 2,5,2',5'-tetra(4'-N,N-diphenylaminostyryl)biphenyl (DPA-TSB). As a potential material for photodynamic therapy, we investigated cellular toxicity by using fluorescence confocal microscopy and Western blotting. Our results demonstrated that the cells treated with DPA-TSB NPs showed an increase in apoptosis accompanied by the increased expression of Bax protein, decreased expression of Bcl-2 protein and caspase-3 protein, the decreased mitochondrial membrane potential and the release of ROS. Using inhibitors of endocytosis can block nanoparticles uptake, indicating that DPA-TSB NPs entered the cells via an energy-dependent manner, mostly through clathrin-mediated and caveolae-mediated processes.

Aluminum local back surface field (Al-LBSF) silicon wafer solar cells are currently intensively investigated in the photovoltaic community and are expected to enter mass production in the near future. In this work we show that this solar cell architecture can pose significant challenges in the determination of the series resistance at the maximum power point. We also show that some of the traditional methods for extracting the series resistance of these cells result in a severe underestimation, due to injection dependent saturation current densities. By using a combination of electro- and photo-luminescence images, we demonstrate that the series resistance of Al-LBSF solar cells can be accurately determined.

For high-efficiency silicon wafer solar cells, Auger recombination is becoming one of the most important efficiency limiting factors. For this purpose it is desirable to be able to use different Auger recombination parameterisations in advanced computer simulations. In this paper we present a method to implement arbitrary Auger parameterisations in the software package Sentaurus TCAD, enabling two- and three-dimensional simulation of solar cells using different Auger parameterisations. As examples, we implemented and investigated three different Auger parameterisations (proposed by Altermatt et al., by Kerr and Cuevas, and by Richter et al.) from the literature. For verification, we simulate Auger lifetimes for different doping densities and injection levels in crystalline silicon. The simulated Auger lifetimes are found to agree well with analytical solutions (differences less than 0.001 %). We then employ the three different Auger parameterisations for fitting measured effective lifetime curves of both \(n\)-type and \(p\)-type float-zone silicon lifetime samples and show which models are applicable under which conditions. We further compare the difference between the three Auger parameterisations by simulating characteristics of a screen-printed aluminium local back surface field silicon wafer solar cell. The simulation results agree well with the characterisation results. We find that the choice of Auger parameterisation can lead to significant differences in the predicted solar cell behaviour under one-Sun illumination. We demonstrate that different Auger parameterisations may result in significant differences in the blue response, by simulating a heavily doped emitter of an aluminium local back surface field silicon wafer solar cell.