The spin-orbit resonances of the Solar system: A mathematical treatment matching physical data

In the mathematical framework of a restricted, slightly dissipative spin-orbit model, we prove the existence of periodic orbits for astronomical parameter values corresponding to all satellites of the Solar system observed in exact spin-orbit resonance

Illumination-Dependent Requirements for Heterojunctions and Carrier-Selective Contacts on Silicon

High efficiency silicon solar cells generally feature heterojunction or carrier-selective contact architectures, for which there is current interest in developing structures using a wide range of materials. The electrical and optical requirements that these layers must fulfill have been investigated previously for standard test conditions. Here, we investigate how the required work functions and layer thickness differ under other illumination conditions. The differences will be important for the optimization of tandem device subcells, and for devices which are intended for use in low-light conditions or under low-level concentration. Heterojunction cells are fabricated and the effect of reduced contact thickness and doping at different illumination levels is experimentally demonstrated. Simulations of a-Si/c-Si heterojunctions and ideal metal-semiconductor junctions reveal a logarithmic variation with illumination level of 0.1-10 suns in the electrode work function, and the heterojunction contact layer work function and thickness required to minimize efficiency losses

Performance Limitations and Analysis of Silicon Heterojunction Solar Cells Using Ultra-Thin MoOx Hole-Selective Contacts

We recently showed that silicon heterojunction solar cell with MoOx-based hole-selective contact could reach 23.5% in efficiency with MoOx layers of 4 nm. Such thin MoOx layer enables a considerable current-density gain of over 1 mA/cm(2) compared to the use of p-type amorphous silicon, and outperforms thicker MoOx layers. In this article, we investigated the impact of the MoOx hole-selective layer for thickness between 0 and 4 nm. Based on optoelectrical characterization of the device at various processing stage, we discuss the optical and electrical effects of such variation on the solar-cell performances. We notably identify a loss of passivation and selectivity for MoOx films thinner than 4 nm, that we link to a reduced work-function for such thin MoOx films. We confirm experimentally that the optimal MoOx thickness is around 4 nm, yet evidence that close to 0.5 mA/cm(2) is still parasitically absorbed in such a thin layer

Hole-Selective Front Contact Stack Enabling 24.1%-Efficient Silicon Heterojunction Solar Cells

The window-layer stack limits the efficiency of both-side-contacted silicon heterojunction solar cells. We discuss here the combination of several modifications to this stack to improve its optoelectronic performance. These include the introduction of a nanocrystalline silicon-oxide p-type layer in lieu of the amorphous silicon p-type layer, replacing indium tin oxide with a zirconium-doped indium oxide for the front transparent electrode, capping this layer with a silicon-oxide film and applying a postfabrication electrical biasing treatment. The influence of each of these alterations is discussed as well as their interactions. Combining all of them finally enables the fabrication of a highly transparent and electrically well-performing window-layer stack, leading to a screen-printed silicon heterojunction solar cell with 24.1% efficiency. Paths toward industrialization and further improvements are finally discussed

Paths for maximal light incoupling and excellent electrical performances in silicon heterojunction solar cells

We discuss here optical losses in silicon heterojunction solar cells and strategies to minimize them. Optical losses originate from most non-crystalline-silicon layers involved in the solar cell. A breakdown for typical values is shown evidencing that suppressing absorption from the front amorphous silicon layers gives the largest gain. Other losses are interdependent, and reducing absorption from one layer in the infrared part of the spectrum boosts absorption from the other layer. The use of nanocrystalline silicon layers in lieu of amorphous silicon enables a reduction of the absorption at a given thickness but thicker layers are seen to be necessary, reducing the eventual optical gain in optimized devices. For the front transparent conductive oxide (TCO), infrared light saved from absorption in the front TCO will be shared between absorption in the c-Si wafer and in the rear electrode, and a share will also be outcoupled from the device through reflection (and transmission in the case of bifacial devices). The cell architecture will therefore dictate how much of the current saved from parasitic absorption in the front TCO will eventually benefit to the device. Using a thin ITO combined with silicon oxide is a route to provide similar electrical performances with reduced indium use and a slight cell-efficiency boost. Switching to a high-mobility Zr-doped indium oxide layer enables to use as thin as 35-nm-thick layers with still low series resistance, which outperforms optically in a cell configuration but yields similar results in a module configuration

A hydrogenated amorphous silicon detector for Space Weather applications

The characteristics of a hydrogenated amorphous silicon (a-Si:H) detector are presented here for monitoring in space solar flares and the evolution of strong to extreme energetic proton events. The importance and the feasibility to extend the proton measurements up to hundreds of MeV is evaluated. The a-Si:H presents an excellent radiation hardness and finds application in harsh radiation environments for medical purposes, for particle beam characterization and, as we propose here, for space weather science applications. The critical flux detection limits for X rays, electrons and protons are discussed