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Francesco Zimbardi

Bio: Francesco Zimbardi is an academic researcher from Georgia Institute of Technology. The author has contributed to research in topics: Passivation & Wafer. The author has an hindex of 10, co-authored 18 publications receiving 365 citations.

Papers
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Journal ArticleDOI
TL;DR: In this paper, the use of ion-implantation for high-volume manufacturing of silicon solar cells is presented, which provides a unique opportunity to obtain grid-parity because it simplifies the fabrication of advanced cell structures.

108 citations

Journal ArticleDOI
TL;DR: In this paper, anon-implanted, screen-printed, high-efficiency, stable, n-base silicon solar cells fabricated from readily available 156mm pseudosquare Czochralski wafers are described, along with prototype modules assembled from such cells.
Abstract: Ion-implanted, screen-printed, high-efficiency, stable, n-base silicon solar cells fabricated from readily available 156-mm pseudosquare Czochralski wafers are described, along with prototype modules assembled from such cells. Two approaches are presented. The first approach, which involves a single phosphorus implant, has been used to produce cells (239 cm2) having a tight distribution of Jsc, Voc, and fill factor over a wide range of wafer resistivity (factor of 10), with Fraunhofer-certified efficiencies up to 18.5%. In spite of the full screen-printed and alloyed Al back, a method has been developed to solder such cells in a module. The second approach, which involves implanting both phosphorus for back-surface field (BSF) and boron for front emitter, has been used to produce n-base cells having local back contacts and dielectric (SiNx/SiO2) surface passivation. Efficiencies up to 19.1%, certified by Fraunhofer, have been realized on 239-cm2 cells. A method is also presented to express recombination activity in the cell base as a component of total reverse saturation current density. This allows recombination activity in all three regions of the cell (n+ region and its surface, n-base, and p+ region and its surface) to be compared as components of the total cell J0 to aid in maximizing Voc.

45 citations

Journal ArticleDOI
TL;DR: In this article, the fabrication of front junction n-type Si solar cells on 239 cm 2 Cz using ion implanted boron emitter and phosphorus back surface field (BSF) in combination with screen printed metallization was reported.

43 citations

Journal ArticleDOI
TL;DR: In this article, the authors reported on in-depth understanding, modeling, and fabrication of 23.8% efficient 4 cm2 n-type float zone (FZ) silicon cells with a selective boron emitter and photolithography contact on front and tunnel oxide passivating contact on the back.
Abstract: This paper reports on in-depth understanding, modeling, and fabrication of 23.8% efficient 4 cm2 n-type Float Zone (FZ) silicon cells with a selective boron emitter and photolithography contact on front and tunnel oxide passivating contact on the back. Tunnel oxide passivating contact composed of a very thin chemically grown silicon oxide (∼15 A) capped with plasma-enhanced chemical vapor deposition (PECVD) grown 20 nm n+ poly Si gave excellent surface passivation and carrier selectivity with very low saturation current density (∼5 fA/cm2). A high-quality boron selective emitter was formed using ion implantation and solid source diffusion to minimize metal recombination and emitter saturation current density. Process optimization resulted in a cell $V_{{\rm{oc}}}$ of 712 mV, $J_{{\rm{sc}}}$ of 41.2 mA/cm2, and FF of 0.811. A simple methodology is used to model these cells which replaces tunnel oxide passivating contact region by electron and hole recombination velocities extracted from measured saturation current density of tunnel oxide passivating contact region and analysis. Using this approach and two-dimensional device modeling gave an excellent match between the measured and simulated cell parameters and efficiency, supporting excellent passivation and carrier selectivity of these contacts. Extended simulations showed that 26% cell efficiency can be achieved with this cell structure by further optimization of wafer quality, emitter profile, and contact design.

37 citations

Journal ArticleDOI
TL;DR: In this article, a fully ion-implanted screen-printed high-efficiency 239 cm2 n-type silicon solar cells that are fabricated on pseudosquare Czochralski wafers were presented.
Abstract: In this study, we present fully ion-implanted screen-printed high-efficiency 239 cm2 n-type silicon solar cells that are fabricated on pseudosquare Czochralski wafers. Implanted boron emitter and phosphorous back-surface field (BSF) were optimized to produce n-type front junction cells with front and back SiO2 /SiNx surface passivation and rear point contacts. Average efficiency of 19.8%, with the best efficiency of 20.2%, certified by Fraunhofer ISE, Freiburg, Germany, was achieved. In addition, the planarized rear side gave better surface passivation, in combination with optimized BSF profile, raised the average efficiency to ~20% for the fully implanted and screen-printed n-type passivated emitter, rear totally diffused cells.

32 citations


Cited by
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Journal ArticleDOI
TL;DR: In this article, the authors review the dynamic field of crystalline silicon photovoltaics from a device-engineering perspective and give an up-to-date summary of promising recent pathways for further efficiency improvements and cost reduction employing novel carrierselective passivating contact schemes, as well as tandem multi-junction architectures, in particular those that combine silicon absorbers with organic-inorganic perovskite materials.
Abstract: With a global market share of about 90%, crystalline silicon is by far the most important photovoltaic technology today. This article reviews the dynamic field of crystalline silicon photovoltaics from a device-engineering perspective. First, it discusses key factors responsible for the success of the classic dopant-diffused silicon homojunction solar cell. Next it analyzes two archetypal high-efficiency device architectures – the interdigitated back-contact silicon cell and the silicon heterojunction cell – both of which have demonstrated power conversion efficiencies greater than 25%. Last, it gives an up-to-date summary of promising recent pathways for further efficiency improvements and cost reduction employing novel carrier-selective passivating contact schemes, as well as tandem multi-junction architectures, in particular those that combine silicon absorbers with organic–inorganic perovskite materials.

751 citations

Journal ArticleDOI
TL;DR: In this article, the efficiency of n-type silicon solar cells with a front side boron-doped emitter and a full-area tunnel oxide passivating electron contact was studied experimentally as a function of wafer thickness W and resistivity ρ b.

470 citations

Journal ArticleDOI
TL;DR: In this paper, the state-of-the-art bifacial solar PV technology is described based on a comprehensive examination of nearly 400 papers published since 1979 (approximately 40% are referenced in this work) focused on illuminating additional research and development opportunities to enhance and assess performance and expand Bifacial technology's overall contribution within a rapidly expanding global solar market.
Abstract: Bifacial solar photovoltaics (PV) is a promising mature technology that increases the production of electricity per square meter of PV module through the use of light absorption from the albedo. This review describes current state-of-the-art bifacial solar PV technology based on a comprehensive examination of nearly 400 papers published since 1979 (approximately 40% are referenced in this work) focused on illuminating additional research and development opportunities to enhance and assess performance and expand bifacial technology׳s overall contribution within a rapidly expanding global solar market. Research and development efforts on bifacial PV should continue to emphasize improved efficiency in cells, module reliability and deployment configuration of bifacial arrays in a PV plant to co-optimize front-backside energy production during the entire day for fixed and tracking systems. Research on improved conversion efficiencies associated with monofacial PV cells will also continue to benefit bifacial PV performance. Standardization of certification procedures for bifacial PV technology performance efficiency and expansion of niche applications is required to promote wider deployment worldwide.

253 citations

Journal ArticleDOI
TL;DR: This work highlights a general approach to improve the performance and stability of Si photoelectrodes by engineering the catalyst/semiconductor interface by incorporatingasma-enhanced atomic layer deposition of cobalt oxide onto nanotextured p(+)n-Si devices.
Abstract: Plasma-enhanced atomic layer deposition of cobalt oxide onto nanotextured p+n-Si devices enables efficient photoelectrochemical water oxidation and effective protection of Si from corrosion at high pH (pH 13.6). A photocurrent density of 17 mA/cm2 at 1.23 V vs RHE, saturation current density of 30 mA/cm2, and photovoltage greater than 600 mV were achieved under simulated solar illumination. Sustained photoelectrochemical water oxidation was observed with no detectable degradation after 24 h. Enhanced performance of the nanotextured structure, compared to planar Si, is attributed to a reduced silicon oxide thickness that provides more intimate interfacial contact between the light absorber and catalyst. This work highlights a general approach to improve the performance and stability of Si photoelectrodes by engineering the catalyst/semiconductor interface.

192 citations

Journal ArticleDOI
TL;DR: In this paper, the use of ion-implantation for high-volume manufacturing of silicon solar cells is presented, which provides a unique opportunity to obtain grid-parity because it simplifies the fabrication of advanced cell structures.

108 citations