E. Salza

Heterojunction solar cell with 2% efficiency based on a Cu2O substrate

We report on the fabrication of heterojunction solar cells made by deposition of transparent conducting oxide (TCO) films on Cu2O substrates. The TCO films have been grown by ion beam sputtering on good quality Cu2O sheets prepared by oxidizing copper at a high temperature. The best solar cell has reached an open-circuit voltage of 0.595V, a short-circuit current density of 6.78mA∕cm2, a fill factor of 50%, and a conversion efficiency of 2% under simulated AM1.5G illumination, which is the highest efficiency value reported for this kind of heterojunction devices. These devices represent a good starting point for the development of very low cost solar cells.

Back Enhanced Heterostructure with INterDigitated contact - BEHIND - solar cell

In this paper we investigate in detail how the heterostructure concept can be implemented in an interdigitated back contact solar cell, in which both the emitters are formed on the back side of the c-Si wafer by amorphous/crystalline silicon heterostructure, and at the same time the grid-less front surface is passivated by a double layer of amorphous silicon and silicon nitride, which also provides an anti-reflection coating. The entire process, held at temperature below 300degC, is photolithography-free, using a metallic self-aligned mask to create the interdigitated pattern. An open-circuit voltage of 695 mV has been measured on this device fabricated. The mask-assisted deposition process does not influence the uniformity of the deposited amorphous silicon layers. Several technological aspects that limit the fill factor are considered and discussed.

Innovative applications of laser technology in photovoltaics

Use of suitable laser systems for photovoltaic devices production has received great attention in recent years, and lasers todays applications range from panel patterning to advanced doping. Mainly when crystalline and polycrystalline silicon are concerned, it seems that lasers can be usefully used to get high efficiency devices in industrial production plants. In this paper, we describe our studies on advanced laser applications for silicon solar cells processing: grooving, texturing, and doping experiments are reported, both on simple structures and on devices, with efficiency values ranging from 15.0% to 16.5%, according to the particular design used. Future developments on schedule in our laboratory, devised to increase cells efficiency and to facilitate lasers use in industrial plants are briefly overviewed.

Silicon Based Photovoltaic Cells For Concentration–Research And Development Progress In Laser Grooved Buried Contact Cell Technology

The Laser grooved buried contact silicon solar cell (LGBC) process employed by Narec currently produces LGBC cells designed to operate at concentrations ranging from 1–100 suns and has demonstrated efficiencies at 50X of over 19% and at 100X of over 18.2% using 300 μm CZ silicon[1] wafers. As part of the LAB2LINE[1], APOLLON[2] and ASPIS[3] projects funded under the European Commission Framework Programs (FP6 and FP7) we have made improvements to the LGBC process to improve efficiency or make the cell technology more suitable for industrial CPV receiver manufacturing processes. We describe a process which hybridizes LGBC and more standard screen printing technologies which yields at least a 6% relative improvement at concentration when using more readily available 200 μm thick CZ wafers. We describe a pioneering front dicing technique (FDT). The FDT process is important in small cells where edge recombination effects are detrimental to the performance. We show that by using this new technique we can produ...

Combinatorial study of co-sputtered Cu 2 ZnSnS 4 thin-film stoichiometry for photovoltaic devices

In this work we investigate the role of stoichiometry variations in Cu2ZnSnS4 thin films obtained via sulfurization of precursor grown by co-sputtering of binary sulphides. Combinatorially graded thin-film Cu-Zn-Sn-S library samples spanning a large region of the ternary Cu2S-ZnS-SnS2 phase diagram were deposited at temperatures below 110°C and subsequently sulfurized at 550°C in a tube furnace using a stoichiometric excess of sulfur. We present some results on the influence of chemical composition, measured by EDX, on the morphological and mechanical properties of the films. The films were also processed to obtain a matrix of small area complete photovoltaic devices. In this way the correlation between the stoichiometry and the device performances can be clarified. Finally, several interesting devices were more completely characterized by measuring J-V characteristic curves, the External Quantum Efficiency (EQE) and by looking at their photoluminescence (PL) spectrum trying to confirm a recently suggested correlation between PL peak energies and photovoltaic performances.

Relevance Of TCO workfunction in n-silicon oxide emitter - c-Si (p) heterojunction solar cell

The amorphous /crystalline silicon heterojunction solar cells have largely demonstrated their usefulness to reach high efficiency. We have adopted a different and wider bandgap emitter based on silicon oxide, n-SiOx. A central role in this type of structure is played from the TCO workfunction whose value affects strongly the heterojunctions band structure at the emitter interface. RF magnetron sputtered TCO obtained with different deposition parameters, have been made in order to optimize their use in our heterojunction solar cell. Numerical simulation on the SiOx HJ, with TCO having proper workfunction value, show potential efficiency conversion well over the 23%. New Roman Bold font. An example is shown next.

Dielectric Bragg back reflecting mirror in a-Si:H / c-Si heterostructure solar cell

In this work we present the design and fabrication of a Bragg reflector, formed on the rear side of an amorphous/crystalline silicon (a-Si/c-Si) n-a-Si/i-a-Si/p-c-Si heterostructure solar cell, in order to obtain an enhancement of the optical confinement of the near-infrared wavelength. The mirror has been grown alternating several couples of amorphous silicon/silicon nitride films whose thicknesses have been optimized, to maximize the reflectance inward the c-Si wafer, using an optical simulator. The cell back contact has been ensured by an Al diffusion into the c-Si wafer promoted by Nd-YAG pulsed laser. The front cell contact has been enhanced by a chromium silicide CrSi formed on top of the n-a-Si layer. A Voc of 681 mV and 94% of internal quantum efficiency at 1000 nm have been achieved.