Influence of defects on silicon heterojunction solar cell efficiency: Physical model and comparison with data

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

Highly efficient 2D materials engineered perovskite/Si tandem bifacial cells beyond 29%

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

Elusive physical electron propagator in QED-like effective theories

We study the previously conjectured form of the physical electron propagator and its allegedly Luttinger type of behavior in the theory of the pseudogap phase of high-temperature copper-oxide superconductors and other effective QED-like models. We demonstrate that, among a whole family of seemingly gauge-invariant functions, the conjectured "stringy ansatz" for the electron propagator is the only one that is truly invariant. However, contrary to the results of the earlier works, it appears to have a negative anomalous dimension, which makes it a rather poor candidate to the role of the physical electron propagator. Instead, we argue that the latter may, in fact, feature a "super-Luttinger" behavior characterized by a faster than any power-law decay: G(x) ~ exp(-const ln^2|x|).Comment: Latex, 10 pages, no figure

Highly Efficient 2D Materials Engineered Perovskite/Si Tandem Bifacial Cells Beyond 29%

International audiencePerovskite/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

The Effects of Module Temperature on the Energy Yield of Bifacial Photovoltaics: Data and Model

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 model that fits the experimental data of module temperature, Isc, Voc, Pmpp, and energy yield. The model was then applied to predict the annual energy yield of PV module strings. The effect of different PV module temperature coefficients on the energy yield is also discussed

Development of Various Photovoltaic‐Driven Water Electrolysis Technologies for Green Solar Hydrogen Generation

Direct solar hydrogen generation via a combination of photovoltaics (PV) and water electrolysis can potentially ensure a sustainable energy supply while minimizing greenhouse emissions. The PECSYS project aims at demonstrating a solar-driven electrochemical hydrogen generation system with an area >10 m2 with high efficiency and at reasonable cost. Thermally integrated PV electrolyzers (ECs) using thin-film silicon, undoped, and silver-doped Cu(In,Ga)Se2 and silicon heterojunction PV combined with alkaline electrolysis to form one unit are developed on a prototype level with solar collection areas in the range from 64 to 2600 cm2 with the solar-to-hydrogen (StH) efficiency ranging from ≈4 to 13%. Electrical direct coupling of PV modules to a proton exchange membrane EC to test the effects of bifaciality (730 cm2 solar collection area) and to study the long-term operation under outdoor conditions (10 m2 collection area) is also investigated. In both cases, StH efficiencies exceeding 10% can be maintained over the test periods used. All the StH efficiencies reported are based on measured gas outflow using mass flow meters

Development of Various Photovoltaic Driven Water Electrolysis Technologies for Green Solar Hydrogen Generation

Direct solar hydrogen generation via a combination of photovoltaics PV and water electrolysis can potentially ensure a sustainable energy supply while minimizing greenhouse emissions. The PECSYS project aims at demonstrating a solar driven electrochemical hydrogen generation system with an area gt;10 amp; 8201;m2 with high efficiency and at reasonable cost. Thermally integrated PV electrolyzers ECs using thin film silicon, undoped, and silver doped Cu In,Ga Se2 and silicon heterojunction PV combined with alkaline electrolysis to form one unit are developed on a prototype level with solar collection areas in the range from 64 to 2600 amp; 8201;cm2 with the solar to hydrogen StH efficiency ranging from amp; 8776;4 to 13 . Electrical direct coupling of PV modules to a proton exchange membrane EC to test the effects of bifaciality 730 amp; 8201;cm2 solar collection area and to study the long term operation under outdoor conditions 10 amp; 8201;m2 collection area is also investigated. In both cases, StH efficiencies exceeding 10 can be maintained over the test periods used. All the StH efficiencies reported are based on measured gas outflow using mass flow meter