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1.
    
Fire‐through Ag thick‐film metallization of crystalline Si (c‐Si) solar cells often yields macroscopically non‐uniform contact quality over the cell area, degrading the cell performance and causing cell‐to‐cell variations of the conversion efficiency in a cell production line. This study analyzes the root cause of the “gray finger” phenomenon, in which part of the fire‐through Ag contact gridlines of a c‐Si solar cell appears in gray or dark contrast in the electroluminescence images owing to high contact resistance. Few Ag crystallites were formed on the corrugated emitter surface at the contact interfaces underneath the gray fingers. The present results revealed that the gray finger phenomenon was caused by a short‐circuit spot that formed between the Ag gridlines and underlying Si emitter during contact firing. The electrochemical reactions involved in fire‐through Ag contact formation established a potential difference between the sintered Ag gridlines and Si emitter separated by molten glass. The molten glass acted as an electrolyte containing mobile Ag+ and O2− ions during contact firing. Therefore, the short‐circuiting between the sintered Ag gridlines and Si emitter produced a galvanic cell during contact firing, which inhibited Ag crystallite formation at the contact interface along the gridlines in a short circuit and produced the gray fingers. The firing reactions in Ag thick‐film contact formation could be interpreted in terms of the mixed potential theory of corrosion. The degradation of cell performance because of the gray finger phenomenon was also evaluated for 6‐in. screen‐printed c‐Si solar cells. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

2.
    
We present n‐type bifacial solar cells with a rear interfacial SiOx/n+:poly‐Si passivating contact (‘monoPoly’ cells) where the interfacial oxide and n+:poly‐Si layers are fabricated using an industrial inline plasma‐enhanced chemical vapor deposition (PECVD) tool. We demonstrate outstanding passivation quality with dark saturation current density (J0) values of approximately 3 fA/cm2 and implied open‐circuit voltage (iVoc) of 730 mV at 1‐sun conditions after firing in an industrial belt furnace. Using a simple solar cell process flow that can be easily adapted for mass production, a peak cell efficiency of 22.8% with a cell open circuit voltage (Voc) of 696 mV is achieved on large‐area, screen‐printed, Czochralski‐silicon (Cz‐Si) solar cells using commercial fire‐through metal pastes.  相似文献   

3.
    
High and stable lifetimes recently reported for n‐type silicon materials are an important and promising prerequisite for innovative solar cells. To exploit the advantages of the excellent electrical properties of n‐type Si wafers for manufacturing simple and industrially feasible high‐efficiency solar cells, we focus on back junction n+np+ solar cells featuring an easy‐to‐fabricate full‐area screen‐printed aluminium‐alloyed rear p+ emitter. Independently confirmed record‐high efficiencies have been achieved on n‐type phosphorus‐doped Czochralski‐grown silicon material: 18·9% for laboratory‐type n+np+ solar cells (4 cm2) with shadow‐mask evaporated front contact grid and 17·0% for front and rear screen‐printed industrial‐type cells (100 cm2). The electrical cell parameters were found to be perfectly stable under illumination. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   

4.
    
This paper analyzes the influence of the composition of screen printing metal pastes on contacting boron emitters for crystalline silicon solar cells, optimized on the basis of commercial Ag‐paste Ferro 3347 by adding silicon and aluminum. Aluminum provides a lower contact resistance, while silicon prevents the spiking and alloying of aluminum with the silicon of the substrate. The best pastes have turned out to be high Si‐concentrated, which have provided a final specific contact resistance of 3–4 mΩ cm2 on screen printed boron emitters diffused at 1000°C for 8 min, with shunt conductance lower than 0.6 mS/cm2. The final fill factors have been better than 77.5% and open circuit voltages have exceeded 605 mV on Czochralski (Cz) n type 0.7 Ω cm solar cells. These results have proven the feasibility of our screen printing process for p+nn+ structures. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

5.
    
We have investigated the influence of diffusion temperature during phosphorus emitter diffusion from a spray‐on source on the performance of screen‐printed multicrystalline silicon solar cells. Because of the dual diffusion mechanism present at high concentration in‐diffusion of phosphorus in silicon, applying lower diffusion temperatures for a longer duration results in significantly enhanced penetration of the low concentration tail relative to the high concentration region. Moreover, we show that the sheet resistance of in‐diffused emitters from a high concentration source depends primarily on the extension of the high concentration region, thus significantly different emitter profiles can be manufactured without altering the sheet resistance considerably. Because of the enhanced tail penetration, emitters of a specified sheet resistance diffused at reduced temperatures can result in higher fill factors of screen‐printed solar cells due to diminution of Schottky type shunts. Furthermore, emitters diffused at lower temperatures for longer durations can yield a higher gettering efficiency, resulting in increased bulk recombination lifetime, and thus a higher internal quantum efficiency at long wavelengths. The deeper tail extension of low temperature emitters, however, causes increased absorption within the highly recombinative emitter, resulting in current losses due to a lower internal quantum efficiency at short wavelengths. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   

6.
We present a practical implementation of a solar thermophotovoltaic (TPV) system. The system presented in this paper comprises a sunlight concentrator system, a cylindrical cup‐shaped absorber/emitter (made of tungsten coated with HfO2), and an hexagonal‐shaped water‐cooled TPV generator comprising 24 germanium TPV cells, which is surrounding the cylindrical absorber/emitter. This paper focuses on the development of shingled TPV cell arrays, the characterization of the sunlight concentrator system, the estimation of the temperature achieved by the cylindrical emitters operated under concentrated sunlight, and the evaluation of the full system performance under real outdoor irradiance conditions. From the system characterization, we have measured short‐circuit current densities up to 0.95 A/cm2, electric power densities of 67 mW/cm2, and a global conversion efficiency of about 0.8%. To our knowledge, this is the first overall solar‐to‐electricity efficiency reported for a complete solar thermophotovoltaic system. The very low efficiency is mainly due to the overheating of the cells (up to 120 °C) and to the high optical concentrator losses, which prevent the achievement of the optimum emitter temperature. The loss analysis shows that by improving both aspects, efficiencies above 5% could be achievable in the very short term and efficiencies above 10% could be achieved with further improvements. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

7.
    
Screen‐print diffusion pastes present an industrially applicable alternative to conventional techniques of dopant deposition. Several commercially available screen‐print dopant pastes are assessed for their suitability in forming heavy selective diffusions for use under metal contacts in silicon solar cells. Pastes are assessed in terms of their ease of application, their ability to form heavy diffusions with low sheet resistances, and their ability to maintain high post‐diffusion wafer lifetimes. Potential for the use of dopant pastes in high‐efficiency solar cell devices is investigated using photoconductance (PC) measurements and photoluminescence (PL) images. It is found that under certain conditions, screen‐print dopant pastes, particularly phosphorus paste, have potential to form effective selective diffusions without significantly compromising performance in high‐efficiency solar cells. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

8.
    
By two‐step sequential Pb2+ adsorption and reaction with methylammonium‐iodide (MAI) or ‐bromide (MABr) at a low concentration level of 0.06–0.10 m over mesoporous TiO2 or ZrO2 film, a well‐defined nanoscale CH3NH3PbI3 (MAPbI3) photosensitizer or CH3NH3PbBr3 (MAPbBr3) light emitter could be prepared in situ, respectively in a reproducible and atom‐economical way. The as‐prepared nanoscale perovskites are compared with their thin film counterparts in terms of light absorption/emission, crystallinity, surface morphology, and energy‐conversion efficiency. The nanoscale perovskite‐decorated films display more transparency than the bulky film due to the much lower amount deposited, while blueshifted and overwhelmingly brighter photoluminescence is observed in the “nano” relative to the “bulk” due to quantum size confinement. Transmission electron microscopy images also clearly show that a few nanometer‐sized perovskite dots are deposited homogeneously over the surface of TiO2‐ or ZrO2‐particulate film in the course of the current preparative route. When the nano‐MAPbI3 is tested as a photosensitizer in a solid‐state dye‐sensitized solar cell configuration with a very thin ( ≈ 650 nm) TiO2 mesoporous film, it has a promising initial power conversion efficiency of 6.23%, which outperformed the result of 2.28% from a typical organic molecular dye coded as MK‐2.  相似文献   

9.
    
We present industrialized bifacial solar cells on large area (149 cm2) 2 cm CZ monocrystalline silicon wafers processed with industrially relevant techniques such as liquid source BBr3 and POCl3 open‐tube furnace diffusions, plasma enhanced chemical vapor deposition (PECVD) SiNx deposition, and screen printed contacts. The fundamental analysis of the paste using at boron‐diffused surface and the bifacial solar cell firing cycle has been investigated. The resulting solar cells have front and rear efficiencies of 16.6 and 12.8%, respectively. The ratio of the rear JSC to front JSC is 76.8%. It increases the bifacial power by 15.4% over a conventional solar cell at 20% of 1‐sun rear illumination, which equals to the power of a conventional solar cell with 19.2% efficiency. We also present a bifacial glass–glass photovoltaic (PV) module with 30 bifacial cells with the electrical characteristics. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

10.
    
A fabrication process for Emitter‐Wrap‐Through solar cells on monocrystalline material with high quality gap passivation by wet thermal silicon dioxide is investigated. Masking and structuring steps are performed by screen‐printing technology. Via‐holes are created by an industrially applicable high‐speed laser drilling process. The cell structure features a selective emitter structure fabricated in a single high temperature step: a highly doped emitter at the via‐holes and the rear side, allowing for a low via‐hole resistivity as well as a low resistivity contact to screen‐printed pastes, and a moderately doped front side emitter exhibiting high quantum efficiency in the low wavelength range. Therefore a novel approach is applied depositing either doped or undoped PECVD silicon dioxide layers on the front side. It is shown that doping profiles advantageous for the EWT‐cell structure can be achieved. The screen‐printed aluminum paste is found to penetrate the underlying thermal dioxide layer at appropriate contact firing conditions leading to a zone of high recombination in the overlap region of aluminum and silicon dioxide. It is shown that conventional PECVD‐anti‐reflection silicon nitride acts as effective protection layer reducing the recombination in this region. Designated area conversion efficiencies up to 18.8% on FZ material are obtained applying the single step side selective emitter fabrication technique. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

11.
    
In this paper, we report on commercially viable screen printing (SP) technology to form boron emitters. A screen‐printed boron emitter and ion‐implanted phosphorus back surface field were formed simultaneously by a co‐annealing process. Front and back surfaces were passivated by chemically grown oxide capped with plasma‐enhanced chemical vapor deposition silicon nitride stack. Front and back contacts were formed by traditional SP and firing processes with silver/aluminum grid on front and local silver back contacts on the rear. This resulted in 19.6% efficient large area (239 cm2) n‐type solar cells with an open‐circuit voltage Voc of 645 mV, short‐circuit current density Jsc of 38.6 mA/cm2, and fill factor of 78.6%. This demonstrates the potential of this novel technology for production of low‐cost high‐efficiency n‐type silicon solar cells. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

12.
    
A novel biosensor based on magnetic nanoparticles (MNPs) functionalized with tyrosinase in an operational synergy with a multiwalled carbon nanotube (MWCNT) network is developed. An on–off external magnetic field is applied to a screen‐printed electrode (SPE), which is used as a transducing platform. This enables an interesting on‐demand biosensing performance. The effect of each component on the response of the developed device is carefully evaluated; particularly interesting results are presented for the contributions of MNPs and carbon nanotubes. A tyrosinase‐based model biosensing approach is used, while a potential of ?0.15 V versus Ag/AgCl for the electrochemical reduction of the enzyme products (quinone forms) onto the magnetoswitchable SPE/MNP/Tyr/MWCNT system is applied. The response of the biosensor to catechol is also evaluated; a limit of detection (signal to noise ratio (S/N) = 3) for catechol is found to be around 7.61 μM (S/N = 3) with a relative standard deviation (RSD) of 4.91% (n = 3). The developed device could open the door to a wide range of novel electrocatalytic and bioelectrocatalytic applications of magnetocontrolled redox enzymes. Furthermore, it could be used in miniaturized and portable biosensing systems, such as lab‐on‐a‐chip devices, in medical and environmental applications that have a restricted quantity of sample. Further applications could be envisaged for many other fields, such as external control of catalytic transformations in bioreactors, tailoring of reversible amperometric immunosensors, regeneration of enzyme‐biosensor electrodes, and external triggering of biofuel cells.  相似文献   

13.
    
Solution‐processed organic photovoltaics (OPVs) have continued to show their potential as a low‐cost power generation technology; however, there has been a significant gap between device efficiencies fabricated with lab‐scale techniques—i.e., spin coating—and scalable deposition methods. Herein, temperature‐controlled slot die deposition is developed for the photoactive layer of OPVs. The influence of solution and substrate temperatures on photoactive films and their effects on power conversion efficiency (PCE) in slot die coated OPVs using a 3D printer‐based slot die coater are studied on the basis of device performance, molecular structure, film morphology, and carrier transport behavior. These studies clearly demonstrate that both substrate and solution temperatures during slot die coating can influence device performance, and the combination of hot substrate (120 °C) and hot solution (90 °C) conditions result in mechanically robust films with PCE values up to 10.0% using this scalable deposition method in air. The efficiency is close to that of state‐of‐the‐art devices fabricated by spin coating. The deposition condition is translated to roll‐to‐roll processing without further modification and results in flexible OPVs with PCE values above 7%. The results underscore the promising potential of temperature‐controlled slot die coating for roll‐to‐roll manufacturing of high performance OPVs.  相似文献   

14.
    
Thin‐film epitaxial silicon solar cells are an attractive future alternative for bulk silicon solar cells incorporating many of the process advantages of the latter, but on a potentially cheap substrate. Several challenges have to be tackled before this potential can be successfully exploited on a large scale. This paper describes the points of interest and how IMEC aims to solve them. It presents a new step forward towards our final objective: the development of an industrial cell process based on screen‐printing for > 15% efficient epitaxial silicon solar cells on a low‐cost substrate. Included in the discussion are the substrates onto which the epitaxial deposition is done and how work is progressing in several research institutes and universities on the topic of a high‐throughput epitaxial reactor. The industrial screen‐printing process sequence developed at IMEC for these epitaxial silicon solar cells is presented, with emphasis on plasma texturing and improvement of the quality of the epitaxial layer. Efficiencies between 12 and 13% are presented for large‐area (98 cm2) epitaxial layers on highly doped UMG‐Si, off‐spec and reclaim material. Finally, the need for an internal reflection scheme is explained. A realistically achievable internal reflection at the epi/substrate interface of 70% will result in a calculated increase of 3 mA/cm2 in short‐circuit current. An interfacial stack of porous silicon layers (Bragg reflectors) is chosen as a promising candidate and the challenges facing its incorporation between the epitaxial layer and the substrate are presented. Experimental work on this topic is reported and concentrates on the extraction of the internal reflection at the epi/substrate interface from reflectance measurements. Initial results show an internal reflectance between 30 and 60% with a four‐layer porous silicon stack. Resistance measurements for majority carrier flow through these porous silicon stacks are also included and show that no resistance increase is measurable for stacks up to four layers. Copyright © 2005 John Wiley & Sons, Ltd.  相似文献   

15.
    
Flatbed screen printing proves to be the dominant metallization approach for mass production of silicon (Si)‐solar cells because of its robust and cost‐effective production capability. However, the ongoing demand of the PV industry to further decrease the width of printed Ag‐electrodes (contact fingers) requires new optimizations. This study presents the latest results on Si‐solar cell metallization using fine‐line screens down to screen opening widths of wn = 15 μm. The best experimental group achieved a record finger geometry with a mean finger width of wf = 19 μm and a mean finger height of hf = 18 μm. Furthermore, solar cell performance using a front‐side grid with a screen opening width of wn = 24 μm is investigated, reporting cell efficiencies up to 22.1% for Passivated Emitter and Rear Contact (PERC) solar cells. Finally, a novel screen pattern simulation is presented, revealing a correlation between the measured lateral finger resistance and the novel dimensionless parameter screen utility index (SUI). It describes the ratio between the average size of individual openings defined by the screen mesh angle and the chosen underlying mesh type. For SUI < 1, the printing result will strongly depend on the screen configuration, whereas for values of SUI > 1, the impact of the screen on the overall printability diminishes.  相似文献   

16.
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17.
    
The in situ formation of an emitter in monocrystalline silicon thin‐film solar cells by solid‐state diffusion of dopants from the growth substrate during epitaxy is demonstrated. This approach, that we denote autodiffusion, combines the epitaxy and the diffusion into one single process. Layer‐transfer with porous silicon (PSI process) is used to fabricate n‐type silicon thin‐film solar cells. The cells feature a boron emitter on the cell rear side that is formed by autodiffusion. The sheet resistance of this autodiffused emitter is 330 Ω/□. An independently confirmed conversion efficiency of (14·5 ± 0·4)% with a high short circuit current density of (33·3 ± 0·8) mA/cm2 is achieved for a 2 × 2 cm2 large cell with a thickness of (24 ± 1) µm. Transferred n‐type silicon thin films made from the same run as the cells show effective carrier lifetimes exceeding 13 µs. From these samples a bulk diffusion length L > 111 µm is deduced. Amorphous silicon is used to passivate the rear surface of these samples after the layer‐transfer resulting in a surface recombination velocity lower than 38 cm/s. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   

18.
    
In this study, the optimum material parameters capable of providing high efficiencies close to the detailed balance limit are determined for intermediate band solar cells. A diffusion model, including the overlap effect between absorption coefficients, is used during the calculations for the first time. It is obtained that to achieve high efficiencies close to the detailed balance limit; the effective density of state value, NCV, should be higher than 1017 cm−3 and the carrier mobility should be larger than 200 cm2/Vs, where the light concentration should not be higher than nearly 1000 sun. Besides, it is found out that the optimum intermediate band level and the base width depend on the mobility and effective density of state values. So they need to be optimized according to the material parameters. The effect of overlap between absorption coefficients on the performance of intermediate band solar cells is also investigated. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

19.
陈东生  李凤  马忠权 《光电子技术》2015,35(2):78-80,100
传统制备P型硅基太阳能电池的方法被应用到N型硅片上,成功制备出n+np+结构的N型硅基太阳能电池。在制备过程中利用补偿法形成np+背结,无需保护背面。最高效率为13.1%(Voc=0.58V,Jsc=31.2mA/cm2,FF=72.4%)。  相似文献   

20.
    
In this work, the back surface field (BSF) formation of locally alloyed Al‐paste contacts employed in recent industrial passivated emitter and rear cell solar cell designs is discussed. A predictive model for resulting local BSF thickness and doping profile is proposed that is based on the time‐dependent Si distribution in the molten Al paste during the firing step. Diffusion of Si in liquid Al away from the contact points is identified as the main differentiator to a full‐area Al‐BSF; therefore, a diffusion‐based solution to the involved differential equation is pursued. Data on the Si distribution in the Al and the resulting BSF structures are experimentally obtained by firing samples with different metal contact geometries, peak temperature times and pastes as well as by investigating them by means of scanning electron microscopy and energy dispersive X‐ray spectroscopy. The Si diffusivity in the Al paste is then calculated from these results. It is found that the diffusivity is strongly dependent on the paste composition. Furthermore, the local BSF doping profiles and thicknesses resulting from different contact geometries and paste parameters are calculated from the Si concentration at the contact sites, the diffusivity and solubility data. These profiles are then used in a finite element device simulator to evaluate their performance on solar cell level. With this approach, a beneficial paste composition for any given rear contact geometry can be determined. Two line widths are investigated, and the effects of the different paste properties are discussed in the light of the solar cell results obtained by simulation. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

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