• Energy Research

One of the major limitations of the nickel (Ni) - yttria-stabilized zirconia (YSZ) anode support for solid oxide fuel cells (SOFC) is its low capability to withstand transients between reducing and oxidizing atmospheres ("RedOx" cycle), owing to the Ni-to-NiO volume expansion. This work presents results on different anode supports fabricated by tape casting. Three compositions are prepared, as the outcome of a preceding design of experiment approach. The NiO proportion is 40, 50 and 60 wt% of the anode composite.

Replacing silver metallization with earth-abundant materials in Si solar cells is a critical step towards the sustainable growth of photovoltaics. In this work, we investigate fire-through processes using Al for the metallization of solar cells with p-type passivating contacts, with the goal to achieve a thin depth of contact, oppositely to what is used for standard back-surface field Al contacts. The interactions taking place during firing between the different elements in our contact stack (Al, SiNx:H, SiCx(p) and tunnel SiOx) are studied. We discuss how Al and SiNx react during firing by performing contact formation through different nitride layers, and show that increasing the N content of the silicon nitride can reduce Al penetration depth. Finally, we also investigate the mechanisms behind metal-induced passivation degradation and identify possible ways of mitigating them by employing an adapted SiOx/SiCx stack to allow for Ag-free metallization of tunnel oxide passivating contacts.

Molybdenum oxide is an efficient hole collector for silicon solar cells. However, its optoelectronic properties deteriorate during cell manufacturing. To assess this issue, the optoelectronic properties and microstructure of molybdenum oxide-based hole contacts are evaluated at different steps of the manufacturing process. Molybdenum oxide becomes more absorbing as it reduces when placed in contact with hydrogenated amorphous silicon, triggering the formation of a 2-nm thick SiO x layer, and when annealed after exposure to the plasma used to sputter the transparent conductive oxide. These changes in the contact properties result in a barrier that impedes hole transport when measuring I–V characteristics at room temperature. Nonetheless, cells still reach an efficiency of up to 20.7% when using a front metal electrode screen-printed at 210 °C (21.7% for reference cells). Above 60 °C, both molybdenum oxide-based and reference cells exhibit the same efficiency as this barrier to hole transport vanishes.

Low‐resistance contact to lightly doped n‐type crystalline silicon (c‐Si) has long been recognized as technologically challenging due to the pervasive Fermi‐level pinning effect. This has hindered the development of certain devices such as n‐type c‐Si solar cells made with partial rear contacts (PRC) directly to the lowly doped c‐Si wafer. Here, a simple and robust process is demonstrated for achieving mΩ cm2 scale contact resistivities on lightly doped n‐type c‐Si via a lithium fluoride/aluminum contact. The realization of this low‐resistance contact enables the fabrication of a first‐of‐its‐kind high‐efficiency n‐type PRC solar cell. The electron contact of this cell is made to less than 1% of the rear surface area, reducing the impact of contact recombination and optical losses, permitting a power conversion efficiency of greater than 20% in the initial proof‐of‐concept stage. The implementation of the LiFx/Al contact mitigates the need for the costly high‐temperature phosphorus diffusion, typically implemented in such a cell design to nullify the issue of Fermi level pinning at the electron contact. The timing of this demonstration is significant, given the ongoing transition from p‐type to n‐type c‐Si solar cell architectures, together with the increased adoption of advanced PRC device structures within the c‐Si photovoltaic industry.

In this paper, we report the preparation of the precursor solutions for the deposition of Cu-Co-Mn-Si oxides by a sot-gel method in order to produce black selective coatings for CSP receiver tubes. Their optical properties were investigated by means of spectroscopic ellipsometry. High Resolution Transmission Electron Microscopy (HRTEM) was used to visualize the microstructure. Time-of-Flight-Secondary-Ion-Mass-Spectroscopy (ToF-SIMS) and X-ray Photoelectron Spectroscopy (XPS) were employed to determine the profile of atomic distribution and their chemical environment in a triple layered coating on a stainless steel (SS) substrate. The studied material shows high potential for the use in multi-layered graded index coatings for solar energy conversion. (C) 2015 Elsevier B.V. All rights reserved.

Light-trapping textures were produced in hyperbranched polymer (HBP) silica nanocomposites using a UV-nanoimprint lithography (UVNIL) replication method, either in batch or roll-to-roll processes. The hardness of the HBP was found to increase by a factor of 2.5 with the addition of 50 vol% of nanoparticles. A nickel master with random sub-micron pyramidal structures was used to imprint nanocomposites containing up to 20 vol% of silica on a polyethylene naphthalate (PEN) substrate. The influence of nanoparticle fraction and pressure on the texture morphology and light scattering properties of the replicas was studied using scanning electron microscopy and optical analysis. The roughness and coherence length of the textures were similar to those of the master for all investigated compositions and process pressures. Likewise, the light scattering performance of aluminum-coated texturized nanocomposites was identical to that of the metal template, with a haze of 90% over the 400-800 nm spectral range. Thin film amorphous silicon solar cells were deposited on the texturized substrates using a large-area roll-to-roll process. The photocurrent of these devices was found to be 23% higher than the reference value of a flat cell.

The detection and quantification of small quantities of Cr in (La,Sr)MnO3/Y–ZrO2 solid oxide fuel cell (SOFC) cathodes by energy-dispersive X-ray spectroscopy (EDXS) is not straightforward as Cr X-ray emission lines overlap with La/Mn and O lines. This work proposes an empirical law correlating the La peak height ratio Lb2.15/La1 to Cr concentrations determined on Cr-doped LSM–YSZ samples characterized by EDXS. Calibration for the law was obtained by chemical analysis of dissolved cathodes. Quantification was confirmed by wavelength-dispersive X-ray spectroscopy.