• Energy Research

Abstract In this paper, a new approach to study the impact of the climate on the optimal sizing of a stand-alone PV/hydrogen/battery-based hybrid building is presented. A general method is described to evaluate the thermal need of the building, as well as the local photovoltaic resource, rather than using specific data available for large purpose applications. The proposed approach enables comparison studies between different places and climatic conditions. Considering a specific autonomous building, a comparative study is provided for different areas worldwide: Moscow, Cairo, Paris, Hanoi and Montreal. A Genetic Algorithm is used to provide an optimal size and energy capacity estimation for each location. The objective is to minimize the total cost while constraining the Loss of Power Supply Probability (LPSP) and the State of Charge (SoC) of the long-term storage element over one year. The sizing results between the different places demonstrate that the local climate has a huge impact on the final price, by highly modifying the PV resource and the thermal need of the building. The results demonstrate an 80% increase variation of the total installation cost between the area of Montreal and the one of Cairo.

The impact of via etching on triple junction solar cell performance has been investigated for through cell via contact architectures. Triple junction solar cells with standard top and back contacts have been fabricated and vias have been etched through the subcells to investigate the new geometry proposed. The external quantum efficiency, the open-circuit voltage ( V oc), the fill factor (FF), and the ideality factor have been measured and compared to those of standard triple junction solar cells without vias. In this way, we evaluate the losses attributable to via etching. Small performance losses from via integration are observed, but performance can be partially restored with an ammonium sulfide passivation treatment. Furthermore, the results show that the V oc losses are almost absent at the high sun concentration that the new architecture is designed for. The source of the performance degradation is correlated with a larger total surface recombination at the edges of the device. The passivation treatment allows an effective surface passivation of the via holes.

International audience; Concentrator photovoltaic (CPV) systems that use silicone-on-glass Fresnel lenses as their primary optical element have reduced power output at high and low lens temperatures. We show that incorporating a nanostructured surface on the solar cell stabilizes best module performance over an extended operating temperature range. We model the optical properties of a self-organized monolayer of glass beads deposited on a polydimethylsiloxane (PDMS) encapsulated solar cell in a CPV sub-module. Our model combines transfer matrix method (TMM), rigorous coupled wave analysis (RCWA), and ray tracing to quickly and accurately simulate the system. We find the short-circuit current gain increases as the lens deviates from its designed working temperature for all bead sizes, and that 400 nm diameter beads submerged halfway into PMDS have the highest gain (up to 2.6%).

International audience

Abstract In this paper, the impact of the plasma process for III-V/Ge heterostructure etching on both the morphology and the photovoltaic performance is investigated for the fabrication of multijunction solar cells with a through cell via contact architecture. Three different plasma chemistries (BCl3/Cl2, SiCl4/Cl2, and SiCl4/H2/Cl2) have been studied in order to obtain anisotropic etching through the multijunction heterostructure without inducing photovoltaic performance loss. SiCl4-based plasma chemistries have been found more suitable to achieve deep via hole etching ( ∼ 30 µm) without lateral etching. The study suggests that SiClx passivation is more efficient to protect the sidewalls compared to BClx. The addition of H2 in SiCl4/Cl2 mixture appears to reinforce the sidewall passivation and thus to limit the lateral etching. III-V/Ge triple junction solar cells with standard grid line and busbar front and back contact have been fabricated on which shallow via-holes have been etched in order to assess the associated photovoltaic performance loss to each plasma etching process. Despite the fact that similar hole sidewall profiles are obtained, the electrical performances are plasma chemistry dependant. This study demonstrates that the SiCl4/H2/Cl2 process presents the lowest losses with almost no induced open-circuit voltage degradation, which makes it promising for the through cell via contact architecture recently proposed for concentrated photovoltaics (CPV) solar cells.

Improving the performances and reducing costs of III-V multijunction solar cells are crucial in aerospatial energy systems and in terrestrial concentrator modules. We attempted to achieve both objectives by implementing non-ohmic metal/semiconductor interface contacts on the front surface of III-V/Ge triple-junction solar cells. We demonstrate the feasibility of this concept for this type of solar cell by a simple evaporation of Al only either on the GaAs contact layer or the AlInP window. The best results were obtained when sulfur passivation by (NH4)2Sx was conducted on the GaAs contact layer. This allowed for a reduction in reverse saturation dark current density by one order of magnitude and a slight increase in Voc of almost 20 mV under 1 sun illumination relative to a reference device with Pd/Ge/Ti/Pd ohmic contacts. However, poor performances were observed at first under concentrated sunlight. Further annealing the solar cells with Al front metallization resulted in the reduction of Voc to the same level as the reference solar cell but allowed for good performances under high illumination. Indeed, an efficiency over 34% was observed at 500 suns light intensity both for Al and Pd/Ge/Ti/Pd contacted solar cells.

International audience ; Micro-Concentrator photovoltaics modules promise to overcome the limitations of CPV such as thermal losses or resistive losses. Miniaturization involves new challenges in the field of cells fabrication, particularly the management of perimeter recombinations. In this paper, sub-millimetric InGaP/InGaAs/Ge solar cells with high performances are fabricated. We report record open circuit voltage of 2.39 V and 2.28 V for cells with mesa area of 0.25 mm 2 and 0.04 mm 2 respectively, indicating excellent sidewall passivation. Individual assessment of sub-cells non-radiative losses indicates that the top cell is the most impacted by perimeter recombinations.