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Papers by cosimo gerardi

Il costo per Watt delle celle solari si e ridotto cosi velocemente negli anni, che i costi di fab... more Il costo per Watt delle celle solari si e ridotto cosi velocemente negli anni, che i costi di fabbricazione dei moduli fotovoltaici incidono poco sui costi totali di un impianto fotovoltaico: sono i costi di installazione e gestione e quelli dei materiali di base che determinano principalmente il costo per la produzione di elettricita. L'aumento di efficienza e l'energia prodotta dall'impianto costituiscono oggi le leve piu importanti per la riduzione dei costi complessivi. La tecnologia dei moduli fotovoltaici si e evoluta nella direzione di massimizzare l'efficienza di conversione e l'energia prodotta in media da un impianto fotovoltaico cercando di ottimizzare la raccolta di luce e ridurre le perdite. In questo lavoro discuteremo dello stato dell'arte della tecnologia fotovoltaica per impiego terrestre che e in gran parte basata sul silicio, il secondo elemento piu abbondante sulla terra, e delle prospettive di sviluppo futuro che puntano a superare i limi...

IOP Conference Series: Materials Science and Engineering

Solar cells cost per Watt has decreased so quickly in the last years that photovoltaic (PV) modul... more Solar cells cost per Watt has decreased so quickly in the last years that photovoltaic (PV) module manufacturing costs cover only a small fraction of the total costs of a PV plant. Essentially, the installation and operation costs as well as the costs for the management of starting materials are the main factors today the most important levers for total costs decrease. PV technology has advanced towards both efficiency and average energy generation increasing by light capture optimization and losses minimization. This work analyses the state-of-the-art of PV technology for terrestrial application and discusses the perspectives for future development, which aims at overwhelming limitation posed by material properties. Higher focus is given to the most promising current technology such as silicon heterojunction solar cells and on future developments based on tandem cell approaches.

Energies, 2021

Bifacial photovoltaics (BPVs) are emerging with large momentum as promising solutions to improve ... more Bifacial photovoltaics (BPVs) are emerging with large momentum as promising solutions to improve energy yield and cost of PV systems. To reach its full potential, an accurate understanding of the physical characteristics of BPV technology is required. For this reason, we collected experimental data to refine a physical model of BPV. In particular, we simultaneously measured the module temperature, short circuit current (Isc), open-circuit voltage (Voc), power at the maximum power point (Pmpp), and the energy yield of a bifacial and a monofacial minimodule. Such minimodules, realised with the same geometry, cell technology, and module lamination, were tested under the same clear sky outdoor conditions, from morning to afternoon, for three days. The bifacial system experimentally shows higher module temperatures under operation, about 10 °C on a daily average of about 40 °C. Nevertheless, its energy yield is about 15% larger than the monofacial one. We propose a physical quantitative ...

2017 IEEE International Reliability Physics Symposium (IRPS), 2017

The Staebler and Wronski light soaking effect [1-3] in hydrogenated amorphous silicon (a-Si:H) re... more The Staebler and Wronski light soaking effect [1-3] in hydrogenated amorphous silicon (a-Si:H) results as a worsening of solar cell performances under light soaking which results in a substantial loss of cell power conversion efficiency compared to time zero performance. In this work, comparing the behavior of single a-Si:H p-i-n devices with that of tandem a-Si:H / microcrystalline Si solar cells, we report on the performance improvement of the solar cells under prolonged exposure to reverse bias DC electric fields and illumination. In the paper we discuss about the radical differences between the forward and reverse bias stress and on the spectroscopic signature of the defects responsible for the instability / improvement effect. In addition, we determine the range of wavelengths where the photons are effective to improve the lifetime and cell efficiency. Finally, examples of reverse bias practical use in solar cell application are shown.

The prediction of energy yield of photovoltaic modules is essential for avoiding energy losses an... more The prediction of energy yield of photovoltaic modules is essential for avoiding energy losses and for marketing purposes. Temperature is one of the most critical factors that influence the efficiency swing of the modules under real-life conditions. Experiments show that the temperature-dependent efficiency model based on conversion efficiency temperature coefficient is inadequate for single and multi-junction modules based on thinfilm silicon technology. Due to the Staebler-Wronski effect, the efficiency depends not only on the temperature at the instant of the measurement but also on the operating temperature history of the module. Here we indicate the module's stabilized efficiency (s) as a meaningful factor for correcting the temperature-dependent efficiency model.

Progress in Photovoltaics: Research and Applications, 2021

Crystalline silicon-based heterojunction (HJ) solar cells are becoming the best choice for manufa... more Crystalline silicon-based heterojunction (HJ) solar cells are becoming the best choice for manufacturing companies, because of the low temperature processes useful for very thin silicon wafers and the possibility to easily achieve cells efficiencies higher than 22% on n-type silicon wafers. However, the maximum cell efficiency is still limited by the typical Fill Factor (FF) value of 82%. This issue is due to several factors, some of which are sometimes underestimated, like the base contact. Indeed, a potential mismatch between the work functions of the transparent conductive oxide and the base doped layer can give rise to a small barrier against electrons collection, which is not easy to recognize when the cell FF overcomes 80%. Also a low doping efficiency of the p-type amorphous layer at the emitter side can negatively affect the FF. In this case, even if high efficiency cells are produced, their full potential is still unexploited. Thus, both selective contacts of the cell, even if apparently optimized to achieve very good results, can hide problems that limit the final cell FF and efficiency. In a previous work, an experimental method and a model to individuate hidden barriers at the base contact on n-type crystalline silicon-based HJs have been provided. In this paper, that model is applied to experimental data obtained from the characterization of both commercial and laboratory level HJ solar cells. Moreover, an easy method to recognize the presence of a barrier to the charge transport at the emitter side of the cell is illustrated.

ROMOPTO '94: Fourth Conference in Optics, 1995

ABSTRACT

IEEE InternationalElectron Devices Meeting, 2005. IEDM Technical Digest., 2005

Here we present an experimental and theoretical analysis of dual-bit DT-NVMs. In particular data ... more Here we present an experimental and theoretical analysis of dual-bit DT-NVMs. In particular data retention experiments on bulk and SOI silicon nanocrystal memory devices (Fig. 1) and their interpretation through a surface potential based model are shown (4). Our model is then exploited to investigate the main issues posed by dual-bit reading, when the dimensions of bulk and SOI devices are scaled down. We present two different reading schemes for a scaled device and we show that dual-bit performance of DT-NVMs, charged on both sides, is preserved even when the two pockets of charge coalesce. Finally, we conclude that both bulk and SOI dualbit architectures are promising for memory cells with gate lengths down to 30-50 nm.

Solar Energy, 2013

In this paper we compare the performance of the textured SnO 2 :F and Mo contacts with the p-type... more In this paper we compare the performance of the textured SnO 2 :F and Mo contacts with the p-type layer in p-in hydrogenate amorphous silicon (a-Si:H) solar cells. We use standard current-voltage (I-V) electrical characterization methods coupled with forward bias small signal impedance analysis. We show the efficacy of this technique to determine the effective carrier lifetime in photovoltaic cells. We show that such effective lifetimes are indeed directly connected to the respective dark diode saturation currents. We also find that the effective lifetime is constant with the temperature in the 0-70°C range and it is significantly better for the solar cell with Mo diode contact. This also explains well the higher open circuit voltage V oc found under illumination in the Mo/p-in cell compared to the SnO 2 :F/pi-n one.

Microelectronic Engineering, 2004

In this paper, we present an overview of memory structures fabricated by our group by using silic... more In this paper, we present an overview of memory structures fabricated by our group by using silicon nanocrystals as storage nodes. These devices show promising characteristics as candidates for future deep-submicron non-volatile memories.

Biomaterials, 2001

The uptake by glass ionomer cement of ions (particularly #uoride) from solutions in which the cem... more The uptake by glass ionomer cement of ions (particularly #uoride) from solutions in which the cements have been immersed has been extensively reported. The concentrations within the cement often greatly exceed those in the immersing solution. The distribution of these ions has not been determined. The aim of this study is to use SIMS to investigate the levels of ions within the cement at di!erent depths below the immersed surface of the cement. K> and F\ were the ions studied and uptake was into a cement containing neither K nor F (LG30) and one containing F (AH2).The surface was analysed using a Cameca ims4f instrument employing a 14.5 keV Cs> primary ion beam. This was calibrated on cements made from a series of glasses in which #uorine content was systematically substituted for oxygen (without other elemental changes). XPS, which is very much a surface technique, was used in con"rmatory role with respect to the SIMS analysis. Cement discs were made from LG30-and AH2-based cements. After maturation for 72 h these were immersed in 0.275% KF solution for 24 h. SIMS analysis indicated appreciable surface F concentration on LG30 and on AH2 an enhanced F concentration. In contrast, K was not detected on the LG30 surface and only at a low level on AH2. These results were con"rmed by XPS. Using the ion beam of the SIMS to sputter away cement enabled the F depth pro"le on LG30 to be measured to 10 m. Over this distance the F content drops from 6.2 mmol/g at 0.2 m from the surface to 0.2 mmol/g at 10 m. No K was detected down to 13 m from the surface. From the results of this study, it can be concluded that SIMS is an appropriate tool for further investigation of the distribution of ions uptaken by glass ionomer cements.

Applied Physics Letters, 2005

In this work, we present an experimental study on the single-electron effects observed at room te... more In this work, we present an experimental study on the single-electron effects observed at room temperature in silicon nanocrystal memories. The electrical characterization has been performed by means of a purposely designed low noise high bandwidth measurement system. Relevant statistical properties of the threshold voltage shifts induced by single-electron trapping and detrapping in the silicon dots are reported. The kinetics of electron capture and emission is also discussed.

Applied Physics Letters, 2008

... Holes, on the contrary, did not feel the field and temperature effects in the ranges relevant... more ... Holes, on the contrary, did not feel the field and temperature effects in the ranges relevant forFlash device applications. ... Dig. - Int. Electron Devices Meet. 2007, 921. Electronic mail: domenico.corso@imm.cnr.it. Present address: Numonyx, Zona Industriale, 95121 Catania, Italy. ...

IEEE Journal of Photovoltaics

Perovskite/Silicon tandem technology represents a promising route to achieve 30% power conversion... more Perovskite/Silicon tandem technology represents a promising route to achieve 30% power conversion efficiency (PCE), by ensuring low levelized costs energy. In this article, we develop a mechanically stacked 2T perovskite/silicon tandem solar cell, with subcells independently fabricated, optimized, and subsequently coupled by contacting the back electrode of the mesoscopic perovskite top cell with the texturized and metalized front contact of the silicon bottom cell. The possibility to separately optimize the two sub-cells allows to carefully choose the most promising device structure for both top and bottom cells. Indeed, semitransparent perovskite top cell performance is boosted through the use of selected two-dimensional materials to tune the device interfaces. In addition, a protective buffer layer is used to prevent damages induced by the transparent electrode sputtering deposition over the hole transporting layer. A textured amorphous/crystalline silicon heterojunction cell fabricated with a fully industrial in-line production process is here used as state of art bottom cell. The perovskite/c-Si tandem device demonstrates remarkable PCE of 28.7%. Moreover, we demonstrate the use of a bifacial silicon bottom cell, as a viable way for overcoming the current matching constrain imposed by the 2T configuration. Here, the current generation difference between perovskite and c-Si cells is compensated by exploiting the albedo radiation thanks to the bifaciality of the commercial c-Si cell used in this article. Considering standard rear irradiation, final power generation density above 32 mW/cm 2 can be achieved, paving the way for a tandem technology customable according to the final installation site.

,(a) C. Gerardi,(b) L. Breuil,(c) C. Jahan,(d) L. Perniola,(d) G. Cina,(b) D. Corso,(a) E. Tripic... more ,(a) C. Gerardi,(b) L. Breuil,(c) C. Jahan,(d) L. Perniola,(d) G. Cina,(b) D. Corso,(a) E. Tripiciano,(b) V. Ancarani ,(b) G. lannaccone,(e) G. Iacono,(b) C. Bongiorno,(a) J. Razafindramora,(d) C. Garozzo,(a) P. Barbera,(a) E. Nowak,(d) R. Puglisi,(a) G. A. Costa,(b) C. Coccorese, (b) M. Vecchio,(b) E. Rimini,(a) J. Van Houdt,(c) B. De Salvo,(d) and M. Melanotte (b) (a) CNR-IMM,

2018 IEEE 7th World Conference on Photovoltaic Energy Conversion (WCPEC) (A Joint Conference of 45th IEEE PVSC, 28th PVSEC & 34th EU PVSEC), 2018

We have realized tandem amorphous Si / microcrystalline Si PV cells and modules with an n+ SiOx e... more We have realized tandem amorphous Si / microcrystalline Si PV cells and modules with an n+ SiOx emitter heterojunction with microcrystalline Si. The SiOx films show filamentary nanostructures and high electrical conductivity. Excellent photovoltaic characteristics are demonstrated.

AIP Advances, 2021

We have studied the influence of defects on silicon heterojunction solar cell efficiency by a met... more We have studied the influence of defects on silicon heterojunction solar cell efficiency by a method based on the comparison of electroluminescence (EL) image data with a finite element circuit model of solar cell efficiency. For this purpose, a general curve that relates the solar cell efficiency to a parameter representative of the defect strength, i.e., the loss of VOC, ∆VOC, from EL maps is obtained, and it is shown that the efficiency can be predicted with a good degree of confidence.

Journal of Applied Physics, 2001

Metal–oxide–semiconductor capacitors in which the gate oxide has been replaced with a silicon ric... more Metal–oxide–semiconductor capacitors in which the gate oxide has been replaced with a silicon rich oxide (SRO) film sandwiched between two thin SiO2 layers are presented and investigated by transmission electron microscopy and electrical measurements. The grain size distribution and the amount of crystallized silicon remaining in SRO after annealing have been studied by transmission electron microscopy, whereas the charge trapping and the charge transport through the dots in the SRO layer have been extensively investigated by electrical measurements. Furthermore, a model, which explains the electrical behavior of such SRO capacitors, is presented and discussed.

We have studied the conversion of thin film photovoltaic factory to Silicon Heterojunction (SHJ) ... more We have studied the conversion of thin film photovoltaic factory to Silicon Heterojunction (SHJ) technology adapting thin film PECVD reactors for deposition of passivation layers. In the transition from thin film to SHJ cells, it is crucial to study the impact of defectiveness on cell efficiency due to several factors such as transportation and handling of wafers. By performing photoluminescence maps and particle contamination analysis on the surface of wafers and cells different defectiveness sources have been studied. Once the sources of defects have been identified, we elaborated solutions to mitigate effects and we were able to increase the efficiency of SHJ solar cells by an absolute gain of 4.3%.