Passivation Stack Research Articles

Simplified process flow for the fabrication of PERC solar cells with ion implanted emitter

Ion implanted PERC cells have already achieved power conversion efficiencies of about 20.0%. The process flows reported in the literature for the ion implanted PERC cells with commonly utilized Al2O3/SiNx rear passivation stack, which has the benefit of being less sensitive to surface roughness than SiO2/SiNx stack passivation, notably suffer from the additional process steps such as single side polishing and single side protection. Here, we present a simplified process flow for the fabrication of ion implanted PERC cells having Al2O3/SiNx stack passivation at the textured rear surface without any rear side processing, leading to a power conversion efficiency of 20% at large area. In this context, we show the sensitivity of solar cell efficiency to firing peak temperature, implantation dose, and Al2O3 thickness. The results of the present research will provide a basis for high efficiency implanted PERC cells with significantly reduced workload and cost.

Correlative analysis of embedded silicon interface passivation by Kelvin probe force microscopy and corona oxide characterization of semiconductor.

We report a correlative analysis between corona oxide characterization of semiconductor (COCOS) and Kelvin probe force microscopy (KPFM) in a study of embedded silicon surfaces in the field of chemical and field-effect passivation. The COCOS approach gives access to the defect density, the total charge contained in the passivation stack, and the potential barrier. Based on the COCOS parameters, we could probe by KPFM to analyze the influence of the passivation stack upon the surface photovoltage. Thus, KPFM emerges as a valuable method to access chemical and field-effect passivation directly. We confirm that it is possible to differentiate by KPFM the influence of local band bending (i.e., field-effect passivation) from the effects due to the local recombination rates (i.e., chemical passivation). The measurements were carried on five different passivation layers of different thicknesses, precisely, 10.5nm SiO2, 50nm SiN, 7nm Al2O3, 7nm HfO2, and a double layer of 7nm Al2O3 below 53nm Ta2O5. Based on our correlative analysis, we could identify by KPFM that HfO2 displays the best chemical passivation properties. Additionally, we confirm that using an anti-reflective coating such as a Ta2O5 layer on top of Al2O3 causes the chemical passivation to deteriorate. Finally, for p-type silicon, SiN appears to be the worst case in terms of field-effect passivation.

Enhanced Conversion Efficiency of Monocrystalline P‐Type Passivated Emitter and Rear Cells in Commercial Production Line by Improving Rear Side Passivation

An industrially proven method for increasing cell efficiency of monocrystalline P‐type PERC cells is reported, whereby a layer of silicon oxide or silicon oxynitride (SiO x /SiO x N y ) is sandwiched between aluminum oxide (AlO x ) and silicon nitride (SiN x ) in the rear passivation stack, forming an AlO x + SiO x /SiO x N y + SiN x structure. This additional layer will theoretically improve the rear side optical and electrical properties for the cell. By adjusting the flow ratio of N2O:NH3, SiO x /SiO x N y with different refractive indices were fabricated. Optimization of the SiO x film thickness showed a 0.11% efficiency gain in monofacial P‐type PERC cells because of higher short‐circuit current (I sc) and fill factor (FF), whereas optimization of the SiO x N y film refractive index showed a 0.05% efficiency gain in bifacial P‐type PERC cells due to the improvement of I sc and FF too. The current gain is believed to be benefited from the optimized light‐absorbing performance of the composite passivation layer structure. Furthermore, it is demonstrated that the refractive index of the SiN x capping layer had to be tuned after the incorporation of SiO x /SiO x N y to improve the cell efficiency.

STEM-EELS investigation of c-Si/a-AlOx interface for solar cell applications

In this article, STEM-EELS methodology is described to investigate the composition of sensitive crystalline Silicon/amorphous aluminum oxide (c-Si/a-AlOx) interface of an a AlOx/amorphous hydrogenated silicon nitride (a-AlOx/a-SiNx:H) passivation stack of a c-Si solar cell. In this stack, a-AlOx has the distinctive characteristic to provide both chemical and field effect passivation, which need further research to be more controlled in order to improve solar cell efficiency. a-AlOx is known to be unstable under the electron-beam, so we first present a detailed study on the electron-beam radiation damage to c-Si/a-AlOx interface. This interface can indeed undergo several electron-beam irradiation damage like sputtering, knock-on or radiolysis if precautions are not taken. Radiolysis damage has been found to be the dominant radiation damage. Thus, several STEM-EELS acquisition parameters like acceleration voltage, electron dose and scan orientation were taken into account and modified to limit this radiolysis damage. Once the irradiation was limited, STEM-EELS investigation was conduct using DualEELS on the Si and Al L2,3 and OK edge fines structures. The interface was found to be composed of a-SiOx and non-stoichiometric aluminum silicate with a predominance of tetrahedrally coordinated Al in its first layer.

Reduced power degradation in bifacial PERC modules by a rear silicon oxide additive layer

In this paper, we investigate the influence of silicon oxide (SiOx) layer on the potential induced degradation (PID) of P-type monocrystalline PERC cells and modules. A SiOx layer was added between the aluminum oxide (AlOx) and silicon nitride (SiNx) layers on the rear side of PERC cells using a newly designed plasma enhanced chemical vapor deposition (PECVD) tool, MAiA from Meyer Burger. The performance of cells and modules with this AlOx + SiOx + SiNx stack was characterized by electrical breakdown (EBD), cell degradation indicator (CDi) and climate chamber PID tests. The EBD test results indicate that the AlOx + SiOx + SiNx stack has higher breakdown voltage than the typically used AlOx + SiNx stack. After undergoing CDi tests, power degradation is more severe in PERC cells with AlOx + SiNx passivation stack than those with AlOx + SiOx + SiNx passivation stack, as evidenced by darker photoluminescence. Bifacial modules made from PERC cells with the AlOx + SiOx + SiNx rear passivation stack demonstrate a significant reduction in rear PID from 12.3% to 4.2%. The results above depict that the addition of a SiOx layer between the AlOx and SiNx layers could effectively reduce the transfer of positive charges from the SiNx layer into the AlOx layer.

Humidity-Sensitive, Demand-Controlled Ventilation Applied to Multiunit Residential Building—Performance and Energy Consumption in Dfb Continental Climate

Humidity-sensitive, demand-controlled ventilation systems have been in use for many years in regions with oceanic climates. Some attempts have been made to apply this technology in Poland, which has a continental climate. This article evaluates the performance and energy consumption of such a system when applied in an eight-floor, multiunit, residential building, i.e., the virtual reference building described by the National Energy Conservation Agency (NAPE), Poland. Simulations using the computer program CONTAM were performed for the whole heating season based upon the climate in Warsaw. Besides passive stack ventilation, that served as a reference, two ventilation systems were studied: one standard and one “hybrid” system with additional roof fans. This study confirmed that the application of humidity-sensitive, demand-controlled ventilation in multiunit residential buildings in a continental climate (Dfb) led to significant energy savings (up to 11.64 kWh/m2 of primary energy). However, the operation of the system on higher floors was found to be ineffective. Ensuring consistent operation of the system on all floors required supplementary fans. The introduction of a hybrid mode reduced carbon dioxide concentrations by approximately 32% in the units located in the upper part of the building. The energetic effect in such cases depends strongly on the electricity source. In the case of the national energy grid, savings of primary energy would be relatively low, i.e., 1.07 kWh/m2, but in the case of locally produced renewable energy, the energy savings would be equal to 5.18 kWh/m2.

Improved Al2O3/SiNx and SiO2/SiNx stack passivation layer structure PERC sc‐silicon solar cells on mass production line

SummaryIn this study, we have successfully developed an industrially feasible stack rear Al2O3/SiNx and front SiO2/SiNx passivation layer PERC solar cells fabrication method based on the existing PERC sc‐silicon solar cells production line. The manufacturing parameters of the deposition processes were adapted to get the best passivation effect. The front SiO2/SiNx passivation layer deposition parameters were researched for the best front passivation effect. The fabrication parameters of the first high refractive index SiNx layer were improved. And a new thin low refractive index SiNx capping layer at SiO2/SiNx interface was introduced. Meanwhile, the stack rear Al2O3/SiNx layer structure with double SiNx layers was also researched, which exhibited good passivation results for the rich hydrogen content in high refractive index SiNx layer. The industrial stack passivation layers PERCs with new thin low refractive index SiNx capping layer possess good performances with an efficiency of 22.15%.

Self-aligned local contact opening and n+ diffusion by single-step laser doping from POx/Al2O3 passivation stacks

Laser doping is a promising route to realise industrially compatible processing of local contacts for high-efficiency solar cells, especially when the same film acts as both dopant source and passivation layer. In this work we demonstrate simultaneous local contact opening and n+ laser doping of silicon from positively charged POx/Al2O3 thin-film stacks, which also provide outstanding passivation of n-type silicon surfaces. Local n+ doped regions with sheet resistance ranging from 35 to ~540 Ω/□ are formed using single nanosecond laser pulses with varying fluence. ECV profiling shows net n-type doping in all cases, confirmed by SIMS profiling to be due to phosphorus from the POx layer. J0 of metallised laser-doped regions is consistent with values achieved for state-of-the-art furnace diffusions with similar sheet resistance, confirming that laser-induced recombination-active defects are avoided. A minimum J0 of 540 fA cm−2 is obtained for metallised laser-doped regions formed from POx/Al2O3 passivation stacks having J0 of 2.5 fA cm−2. The combination of outstanding passivation of uncontacted n-type regions offered by POx/Al2O3, with self-aligned formation of locally-diffused contact openings via single-step laser processing, opens up exciting possibilities for simplified fabrication of high-efficiency cell structures.

Gate Reliability and its Degradation Mechanism in the Normally OFF High-Electron-Mobility Transistors With Regrown p-GaN Gate

Gate reliability and its degradation mechanism were studied for the normally off high-electron-mobility transistors (HEMTs) with regrown p-GaN gate and AlN/SiN <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</sub> stack passivation. Through comparing the forward leakage current in two designed structures, the conduction mechanism is determined to be Fowler-Nordheim tunneling whose current is independent of temperature when the Pd/p-GaN Schottky junction is under high electric field. Even for the regrown p-GaN gates, this Schottky junction fails at first, resulting in an abrupt increase in gate current. The maximum gate operation voltage with a failure rate of 1% for 10-year lifetime is estimated to be about 6.87 and 6.07 V at room temperature by adopting power law and exponential law as extrapolation fitting, respectively. Degradation process monitoring reveals that the net acceptor concentration N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">A</sub> extracted through C- V fitting presents an apparent decreasing trend from 3.8×10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">19</sup> to 1.1×10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">19</sup> cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-3</sup> with the stress time increased from 30 to 2600 s. This is assumed to be related with the defects generation in the Schottky depletion region under high tunneling current and high electric field. These analyses show the feasibility of the normally off HEMTs with a regrown p-GaN gate and AlN/SiN <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</sub> stack passivation for practical applications, giving directions for further improving the gate breakdown voltage and lifetime.

A novel bandwidth enhanced triple band antenna for satellite and airborne applications

&lt;p align="justify"&gt;&lt;span&gt;This paper presents a novel bandwidth enhancement technique in which a passive stack of third order Sierpinski carpet fractal antenna is parasitically coupled to the driven element that is also a Sierpinski fractal of third order. Edge feeding technique is used. The passive stack placed symmetric to the driven elements provide the combined benefits of horizontal and vertical parasitic coupling, with added advantage of miniaturization contributed by fractal technology. Result of the study indicate that the antenna array provide triple band with a large inter-band separation that mitigates the effects of inter-band interference. The first band at 6.1Ghz with bandwidth of 250Mhz supports mobile wireless and fixed satellite service, the second band at 7.1Ghz with 350Mhz bandwidth supports mobile wireless, fixed wireless and fixed satellite service. The third band is at 11.6Ghz with bandwidth of 1.4Ghz and supports fixed wireless and fixed satellite services. The number of elements in the parasitic stack influence array performance in terms of bandwidth, gain and directivity. The bandwidth in the third band increased from 1.5Ghz for two-element stack to 1.7Ghz for three-element. This has an advantage over conventional antenna array, that use more active antenna elements that have the limitations of more power consumption and large space occupancy. &lt;/span&gt;&lt;/p&gt;

Ultrathin barrier AlGaN/GaN hybrid‐anode‐diode with MOCVD in‐situ Si 3 N 4 ‐cap and LPCVD‐Si 3 N 4 bilayer passivation stack for dynamic characteristic improvement

A novel ultrathin barrier AlGaN/GaN hybrid-anode-diode (UTB-HAD) with in-situ Si 3 N 4 -cap passivation is experimentally demonstrated. The forward turn-on voltage ( V on ) of the UTB-HAD is determined by the intrinsic threshold voltage of the two-dimension electron gas (2DEG) channel, which can be precisely controlled by tailoring the as-grown AlGaN-barrier thickness. The typical V on as low as 0.48 V is obtained by using the UTB AlGaN/GaN with a barrier thickness of 4.9 nm. The MOCVD has grown in-situ Si 3 N 4 -cap and the LPCVD-Si 3 N 4 bilayer passivation stack is developed to effectively restore the 2DEG in the UTB AlGaN/GaN heterostructure and simultaneously improve the dynamic characteristics of the diode. The UTB-HAD and the novel passivation scheme are of great potential for power applications.

Influence of layer thickness on passivation properties in SiOx/Al2O3 stacks

SiOx/Al2O3 passivation stacks have shown the potential to effectively passivate both n- and p-type surfaces as the charge density may be controlled via the SiOx layer thickness. Here, the passivation quality of the SiOx/Al2O3 stacks is investigated as the function of SiOx layer thickness and Al2O3 layer thickness. The SiOx/Al2O3 passivation stacks were deposited on n- and p-type Si using plasma-enhanced atomic layer deposition and the effective surface recombination velocity (Seff), interface defect density (Dit), and effective fixed charge density (Qeff) were measured. The level of passivation was highest when the surface was passivated with only Al2O3 (1.1 cm/s and 4.8 cm/s for n-type and p-type, respectively). Seff increased with increasing SiOx thickness, reached a maximum value, and then decreased for thicker SiOx layers. The low Seff values correlate with accumulation or inversion while maximum Seff appears at the depletion/edge of inversion. Increasing the Al2O3 thickness also lowered Seff, both when used on its own and in SiOx/Al2O3 stacks but did not affect where the maximum Seff was located. The defect density was low (Dit&amp;lt;1011eV−1cm−2) irrespective of SiOx thickness and the n-type wafers showed an overall lower defect density than p-type wafers. The SiOx layer lowered the defect density for n-type wafers and Dit&amp;lt;1010eV−1cm−2 could be observed. The SiOx layer thickness greatly affected the effective fixed charge density (Qeff) which became more positive as the thickness increased. The doping type had an influence on the resulting Qeff with the n-type Si becoming more negatively charged than p-type.

Experimental study on boiling performance of wetting fluids in three-dimensional rectangle microchannels

A unique boiling heat transfer study of wetting fluids in a vertical three-dimensional rectangle microchannel was carried out in this paper, to develop a novel passive three-dimensional chip stack cooling technology. The base liquids were deionized water and R113, and Sodium dodecagon sulfate (SDS) was used as a surfactant, which is added into the base fluids for developing wetting fluids. The length, gap, and width of rectangle channels were in the range of 30 mm to 100 mm,30 mm to 50 mm, and 0.4 mm to 4 mm, respectively. Metal wires with different numbers were laid in the rectangle channel along the flow direction for forming change in the width of the microchannel. The study results show that using wetting fluids can significantly enhance both heat transfer coefficients and maximum heat flux of thermosyphon boiling in three-dimensional microchannels compared with that found in pure liquids. The enhanced effects have significant relations with the three-dimensional geometric dimensions. The present experimental results provide significant technology support for passive three-dimensional chip cooling.

Low-cost silicon neural probe: fabrication, electrochemical characterization and in vivo validation

This paper presents the fabrication of a silicon neural probe using low-cost microfabrication technologies, such as thin-films deposition, blade dicing, and photolithography. The metal stack that forms the 9 microelectrodes of 50 × 50 µm2 area, the tracks and the pads were made of Ti and Pt, while the passivation stack was SiO2 and Si3N4. The fabricated probe was characterized using electrochemical impedance spectroscopy, before and after deposition of poly(3,4-ethylene-dioxythiophene) (PEDOT) on Pt microelectrodes. The electrochemical deposition of PEDOT, a conductive polymer, reduced the impedance of the Pt microelectrodes. The neural probe with PEDOT was used for in vivo electrophysiological acute recordings in an adult rat. The extracellular recordings were filtered to obtain the spike and local field potential (LFP) data, using Butterworth bandpass filters of 400–6000 Hz and 0.1–300 Hz, respectively. The results obtained with the fabricated neural probe validated its functionality, comparing with the signals acquired with a commercial neural probe, and the viability of the fabrication process, which avoids high–cost and complex etching processes.

Methodology for design decision support of cost-optimal zero-energy lightweight construction

The interest to find cost-optimal zero-energy solutions for building, using multi-objective optimization, has risen dramatically over the last decade. Accordingly, several studies have been carried out, proposing new methods and tools. None, however, has introduced a simplified approach that is viable by a broader range of users. This study addresses this lack, offering a methodology that supports the decision making process on cost-optimal zero energy building, using a novel approach, namely Multi-Objective Parametric Analysis (MOPA), rather than optimization algorithms. This study adds to the domain of roof stacking construction by setting the weight of construction as a third objective. The current methodology is applied to a newly developed theoretical Reference Building (RB) for a Belgian passive roof stacking house. Different options of the building’s superstructure components (walls, roof, and windows) have been examined. MOPA follows three consecutive steps: modeling setup, parametric simulation, and ends up with evaluation and selection. The results show cost-optimal zero-energy and lightweight packages of design variables for the building envelope.

Effect of Laser Ablation on Rear Passivation Stack for N-type Bifacial Solar Cell Application

In this paper, we investigated the effect of the passivation stack with Al2O3, hydrogenated silicon nitride (SiNx:H) stack and Al2O3, silicon oxynitride (SiONx) stack in the n type bifacial solar cell on monocrystalline silicon. SiNx:H and SiONx films were deposited by plasma enhanced chemical vapor deposition on the Al2O3 thin film deposited by thermal atomic layer deposition. We focus on passivation properties of the two stack structure after laser ablation process in order to improve bifaciality of the cell. Our results showed SiNx:H with Al2O3 stack is 10 mV higher in implied open circuit voltage and 60 μs higher in minority carrier lifetime than SiONx with Al2O3 stack at Ni silicide formation temperature for 1.8% open area ratio. This can be explained by hydrogen passivation at the Al2O3/Si interface and Al2O3 layer of laser damaged area during annealing.

Characterization of Electrode with Various of Pt-Ru/C Catalyst Loading and the Performance Test of Membrane Electrode Assembly (MEA) in Passive Direct Methanol Fuel Cell (DMFC)

Membrane Electrode Assembly (MEA) is the most important component in fuel cell devices. Electrodes composing MEA greatly determine the performance and durability of its application in passive Direct Methanol Fuel Cell (DMFC). Fabrication and characterization of electrodes with various loading Pt-Ru/C catalysts and their application to DMFC have been carried out. The XRD characterization results indicate the presence of C atoms which are indicated by the appearance of peaks at angles 2θ = 25°-30°. In areas, 44.4° and 45.1° indicate the presence of Ru even with low intensity and platinum in the area of 54.67°, 39.86°, 54.736°, 39.88°, and 68.3°. The highest ECSA value and electrical conductivity and low resistance showed the best catalytic activity possessed by electrodes with the loading of Pt-Ru/C catalyst 10 mg/cm2. MEA with a catalyst loading of 8 mg/cm2 is known to have a fairly large initial voltage before the load is given based on the results of Open Circuit Voltage (OCV) measurements. The MEA performance was observed based on I-V and I-P performance tests using the SMART2 WonAtech Fuel Cell Test Station on passive DMFC stacks with 3 M methanol as fuel. The best MEA shown in MEA with catalyst loading is 10 mg/cm2 because it can maintain and achieve a voltage and power density that is quite higher than other MEAs in each load increase in the form of current density.

Mechanism of Metallization-Induced Losses in the Rear-Side of Fully Screen-Printed p-type PERC Solar Cells

This article investigates metallization-induced recombination losses associated with the presence of silicon (Si) in the 1) rear passivation layers and 2) aluminum (Al) paste in fully screen-printed p -type passivated emitter and rear cell (PERC) solar cells. For 1), the rear sides of PERCs passivated with aluminum oxide films stacked with silicon nitride (SiN y ) films with various refractive indexes (n), as defined by the composition of the SiN y films, were fabricated. Si-rich SiN y films strongly degraded the implied open-circuit voltages of symmetrically passivated samples, that include cells. Elemental mapping analysis confirmed further metallization-induced losses at the cell level because of the formation of an Al-Si alloy within the passivation stacks, with the density of the alloy dependent on the refractive index. For 2), the rear sides of PERCs were metallized with Si-free Al paste or Al pastes that contain Si. High-Si paste had both good and bad effects: it produced thicker aluminum back surface fields but left partially-formed Al-Si alloy within the passivation films.

Surface passivation in n-type silicon and its application in silicon drift detector**Project supported by the National Natural Science Foundation of China (Grant Nos. 51602340, 51702355, and 61674167), the Natural Science Foundation of Beijing Municipality of China (Grant No. 4192064), the National Key Research Program of China (Grant Nos. 2018YFB1500500 and 2018YFB1500200), and the JKW Project of China (Grant No. 31512060106).

Based on the surface passivation of n-type silicon in a silicon drift detector (SDD), we propose a new passivation structure of SiO2/Al2O3/SiO2 passivation stacks. Since the SiO2 formed by the nitric-acid-oxidation-of-silicon (NAOS) method has good compactness and simple process, the first layer film is formed by the NAOS method. The Al2O3 film is also introduced into the passivation stacks owing to exceptional advantages such as good interface characteristic and simple process. In addition, for requirements of thickness and deposition temperature, the third layer of the SiO2 film is deposited by plasma enhanced chemical vapor deposition (PECVD). The deposition of the SiO2 film by PECVD is a low-temperature process and has a high deposition rate, which causes little damage to the device and makes the SiO2 film very suitable for serving as the third passivation layer. The passivation approach of stacks can saturate dangling bonds at the interface between stacks and the silicon substrate, and provide positive charge to optimize the field passivation of the n-type substrate. The passivation method ultimately achieves a good combination of chemical and field passivations. Experimental results show that with the passivation structure of SiO2/Al2O3/SiO2, the final minority carrier lifetime reaches 5223 μs at injection of 5×1015 cm−3. When it is applied to the passivation of SDD, the leakage current is reduced to the order of nA.

Performance and Ethanol Crossover of Passive Direct Ethanol Fuel Cell Stack

A dual-cell passive direct ethanol fuel cell (DEFC) stack with single ethanol tank was designed and tested to obtain the voltage requirement of electronics and to reduce weight and volume for practical applications. Ethanol crossover and cell performance were determined at different ethanol feed concentrations. Characterization techniques were used, including a cell polarization tests, a long-term steady voltage discharging measurement, and an electrochemical impedance spectroscopy (EIS). It was found that, before long-term steady voltage test, the optimum ethanol feed concentration was 2 M. The ethanol crossover increases with ethanol concentration increment over 2 M and the ethanol crossover exhibited a negative effect on the open circuit voltage (OCV) and the cell performance. However, after a long-term steady voltage test, the best ethanol feed concentration was changed to 3 M. It was due to the difference of current density discharged during long-term operation. It can also be found that, after long-term steady voltage test, the cell resistance was apparently reduced. It may be explained that the mass transport of both liquid fuel and air as a reactant in the cell structure reached equilibrium during long-term operation.