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[IEEE 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - Chicago, IL, USA (2019.6.16-2019.6.21)] 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - Performance characterization for bifacial photovoltaic modules
摘要： The performance of bifacial photovoltaic modules were characterized. The optical transmittance was measured for front and back side illumination. The temperature coefficients were obtained in order to predict the real power that can be produced in an installation under operating conditions. The internal quantum efficiency distribution was measured to distinguish recombination activity which occurred at the silicon via two-dimensional LBIC method.
关键词： optical transmittance spectra,temperature coefficient,bifacial perc solar cells,quantum efficiency
更新于2025-09-23 15:21:01
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Omni-direction PERC solar cells harnessing periodic locally focused light incident through patterned PDMS encapsulation
摘要： Photovoltaic panels based on crystalline Si solar cells are the most widely utilized renewable source of electricity, and there has been a significant effort to produce panels with a higher energy conversion efficiency. Typically, these developments have focused on cell-level device modifications to restrict the recombination of photo-generated charge carriers, and concepts such as back surface field, passivated emitter and rear contact (PERC), interdigitated back contact, and heterojunction with intrinsic thin layer solar cells have been established. Here, we propose quasi-Fermi level control using periodic local focusing of incident light by encapsulation with polydimethylsiloxane to improve the performance of solar cells at the module-level; such improvements can complement cell-level enhancements. Locally focused incident light is used to modify the internal quasi-Fermi level of PERC solar cells owing to the localized photon distribution within the cell. Control of the local focusing conditions induces different quasi-Fermi levels, and therefore results in different efficiency changes. For example, central focusing between fingers enhances the current density with a reduced fill factor, whereas multiple local focusing enhances the fill factor rather than the current density. Here, these effects were explored for various angles of incidence, and the total electrical energy production was increased by 3.6% in comparison to a bare cell. This increase is significant as conventional ethylene vinyl acetate-based encapsulation reduces the efficiency as short-wavelength light is attenuated. However, this implies that additional module-scale studies are required to optimize local focusing methods and their synergy with device-level modifications to produce advanced photovoltaics.
关键词： quasi-Fermi level control,module-level enhancements,energy conversion efficiency,Photovoltaic panels,crystalline Si solar cells,local focusing,polydimethylsiloxane,PERC solar cells
更新于2025-09-23 15:19:57
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Bifacial p-Type PERC Solar Cell with Efficiency over 22% Using Laser Doped Selective Emitter
摘要： In this paper, we report one bifacial p-type PERC solar cell with e?ciency over 22% using laser doped selective emitter produced in larger-scale commercial line on 6-inch mono-crystalline wafer. On front side of the solar cell, square resistance of p-n junction was found to be closely related with laser power at certain laser scan speed and frequency. On the other side, the rear ?ngers with di?erent ratios of height and width and rear silicon nitride (SiNx) layer with di?erent thickness were optimized, and a highest rear e?ciency of the bifacial solar cell was obtained. Finally, bifacial silicon solar cells with the front and rear e?ciencies exceeding 22% and 15% (AM1.5, 1000 W/m2, 25 C) were successfully achieved, respectively.
关键词： p-type,bifacial,passivated emitter and rear (PERC) solar cells,laser doped selective emitter
更新于2025-09-23 15:19:57
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Random nanohole arrays and its application to crystalline Si thin foils produced by proton induced exfoliation for solar cells
摘要： We report high efficiency cell processing technologies for the ultra-thin Si solar cells based on crystalline Si thin foils (below a 50 μm thickness) produced by the proton implant exfoliation (PIE) technique. Shallow textures of submicrometer scale is essential for effective light trapping in crystalline Si thin foil based solar cells. In this study, we report the fabrication process of random Si nanohole arrays of ellipsoids by a facile way using low melting point metal nanoparticles of indium which were vacuum-deposited and dewetted spontaneously at room temperature. Combination of dry and wet etch processes with indium nanoparticles as etch masks enables the fabrication of random Si nanohole arrays of an ellipsoidal shape. The optimized etching processes led to effective light trapping nanostructures comparable to conventional micro-pyramids. We also developed the laser fired contact (LFC) process especially suitable for crystalline Si thin foil based PERC solar cells. The laser processing parameters were optimized to obtain a shallow LFC contact in conjunction with a low contact resistance. Lastly, we applied the random Si nanohole arrays and the LFC process to the crystalline Si thin foils (a 48 μm thickness) produced by the PIE technique and achieved the best efficiency of 17.1% while the planar PERC solar cell without the Si nanohole arrays exhibit 15.6%. Also, we demonstrate the ultra-thin wafer is bendable to have a 16 mm critical bending radius.
关键词： proton implant exfoliation,random Si nanohole arrays,PERC solar cells,ultra-thin Si solar cells,light trapping,laser fired contact
更新于2025-09-16 10:30:52
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AIP Conference Proceedings [AIP Publishing INTERNATIONAL SYMPOSIUM ON GREEN AND SUSTAINABLE TECHNOLOGY (ISGST2019) - Perak, Malaysia (23–26 April 2019)] INTERNATIONAL SYMPOSIUM ON GREEN AND SUSTAINABLE TECHNOLOGY (ISGST2019) - Lead-free solders for ribbon interconnection of crystalline silicon PERC solar cells with infrared soldering
摘要： We report about the analysis of Pb-free, low-temperature solders for the ribbon-interconnection of PERC solar cells with an industrial infrared stringer. Five solders (SnPb, SnBi-A, SnBi-B, SnBiAg and a proprietary lead-free, low-temperature (PLFLT) alloy) are characterized with di?erential scanning calorimetry to determine the melting and solidi?cation temperature. It is found that SnBi-B, SnBiAg, and the PLFLT composition melt in a temperature range between 137 ?C to 171 ?C instead of a single temperature. Solidi?cation occurs at a 3 K to 11 K lower temperature (undercooling). Mono-crystalline silicon PERC cells are contacted using an industrial stringer. The microstructure of the solder bonds is investigated with scanning electron microscopy. For the SnBi-A-solder, large and brittle Bi-phases are identi?ed. The SnBi-B, SnBiAg and PLFLT solder show a ?ner grain structure. The added Ag in SnBiAg forms an intermetallic compound of Ag3Sn close to the Cu-core of the ribbon. The peel strength of the connected solar cells with the Pb-free solders is on average 1 N mm?1 or slightly higher. Some bonds show low adhesion. The observed fracture mode is mainly failure at the busbar metallization to solar cell irrespective of the solder type. However, the occasionally observed solder residues on the metallization clearly reveal brittle fracture for the Pb-free solders, which is not observed for SnPb. First reliability tests show similar degradation of 1 % to 2 % for all solders.
关键词： ribbon interconnection,infrared soldering,lead-free solders,crystalline silicon PERC solar cells
更新于2025-09-16 10:30:52
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AIP Conference Proceedings [AIP Publishing 15th International Conference on Concentrator Photovoltaic Systems (CPV-15) - Fes, Morocco (25–27 March 2019)] 15th International Conference on Concentrator Photovoltaic Systems (CPV-15) - Adaptation of the industrial PERC solar cell process chain to plated Ni/Cu/Ag front contact metallization
摘要： Three approaches to close the efficiency gap between screen-printed Ag-paste and Ni/Cu/Ag-plated front contact metallization on industrial passivated emitter and rear cells (PERC) solar cells are presented in this paper. In the first approach, the POCl3 diffusion is adjusted to an emitter profile (reduced peak doping) for plated contacts. The second approach is to adapt the laser over doping (LOD) process of the phosphor silicate glass (PSG) to create the selective emitter to the properties of laser patterning and plating. In the third approach, we vary the process step order of front laser patterning and back side aluminum firing. The three approaches show very promising results. Efficiencies higher than 22% and open-circuit voltage VOC values of close to 680 mV are reached on a cell area of 251,99cm2. Overall the values excel the reference values obtained with screen printing and firing of Ag-paste. For future developments, VOC values between 685 mV and 690 mV and efficiencies around 22.5% seem very likely.
关键词： laser over doping,Ni/Cu/Ag-plated front contact,PERC solar cells,selective emitter,POCl3 diffusion
更新于2025-09-12 10:27:22
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AIP Conference Proceedings [AIP Publishing 15th International Conference on Concentrator Photovoltaic Systems (CPV-15) - Fes, Morocco (25–27 March 2019)] 15th International Conference on Concentrator Photovoltaic Systems (CPV-15) - Impact of the thermal budget of the emitter formation on the pFF of PERC+ solar cells
摘要： We develop processes for advanced phosphorus doping profiles in order to reduce the emitter saturation current density Jo,e of industrial bifacial PERC+ solar cells. With an in-situ oxidation, which takes place in the POCl3 furnace in between the deposition and the drive-in step, the surface concentration was lowered from 3 × 1020 cm-3 to 1.7 × 1020 cm-3. With an additional ex-situ oxidation, which takes place after the phosphorus silicate glass is removed, the phosphorus surface concentration was further reduced to 3 × 1019 cm- 3. The decreased phosphorus surface concentration drastically reduces Jo,e from 106 fA/cm2 down to 22 fA/cm2. The reduced Jo,e increases the implied open circuit voltage up to 712 mV of unmetallized PERC+ test structures and the Voc of PERC+ solar cells up to 678 mV and efficiencies up to 21.8%. However, our solar cell analysis reveals for the first time, that with increasing thermal budget of the applied POCl3 and oxidation recipes the pseudo fill factor (pFF) decreases by up to 1.5%. This corresponds to an efficiency loss of approximately 0.5%abs. We analyse the pFF loss based on different lifetime test structures representing the emitter or the bulk of the PERC+ solar cell. From the lifetime measurements we calculate I-V curves representing the implied fill factor (iFF) of the different parts of the PERC+ solar cell as well as a combined one for the whole cell, which compares well to the measured pFF. The iFF values clearly show that the pFF is mainly limited by wafer bulk material. However, also the iFF values of the emitter slightly decrease with increasing thermal budget.
关键词： in-situ oxidation,phosphorus doping profiles,pseudo fill factor,ex-situ oxidation,emitter saturation current density,PERC+ solar cells,thermal budget
更新于2025-09-12 10:27:22
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AIP Conference Proceedings [AIP Publishing 15th International Conference on Concentrator Photovoltaic Systems (CPV-15) - Fes, Morocco (25–27 March 2019)] 15th International Conference on Concentrator Photovoltaic Systems (CPV-15) - Excess charge carrier injection densities in PERC solar cells at open-circuit voltage and maximum power point
摘要： Nowadays passivated emitter and rear contact (PERC) solar cells are mainstream cell technology. An accurate knowledge of the excess charge carrier injection density during illumination will help to understand the kinetic behavior of charge carrier sensitive defects such as boron-oxygen related defect, LeTID defect or FeB pair dissociation and thus supports reliability improvements of PERC cells. However, the excess charge carrier injection density is not easily accessible in experiments. The aim of our research is to investigate the distribution of the injection density in PERC cells in the range of 22% to 24% efficiency. Thus, we perform a numerically simulated Design of Experiment varying the base resistivity and the location of recombination to derive the excess charge carrier injection density. However, no relevant combined influences of the location of recombination on the injection density are found. The base averaged excess charge carrier injection density increases with higher PERC efficiencies as well as with higher specific resistivity of the base. For a sufficient description of the injection density at open-circuit condition, the law of mass action under applied voltage considering high-level injection can be used to calculate the injection density. At maximum power point voltage, an effective voltage at the pn-junction is derived considering the voltage drop due to the lumped series resistance. This effective voltage is used to calculate an injection density with the law of mass action considering high level injection.
关键词： base resistivity,recombination,PERC solar cells,maximum power point,open-circuit voltage,excess charge carrier injection density
更新于2025-09-11 14:15:04