• Energy Research

This study focuses on the mapping of oxygen-related defects in industrial monocrystalline silicon wafers. All mappings were obtained solely from resistivity measurements and specific furnace anneals. An emphasis is given on the boron-oxygen complex responsible for the light-induced degradation (LID) of the carrier lifetime in boron-doped wafers. It is shown that the predicted values for the lifetime limited by the boron-oxygen complexes after complete degradation are in very good agreement with the experimental observations. It is also shown that the present technique is a valuable tool to predict the cell LID from measurements on as-received wafers, which is of paramount interest for wafer/cell manufacturers. 28th European Photovoltaic Solar Energy Conference and Exhibition; 902-906

This work aims at the full recovery of efficiency losses induced by shingling double-side poly-Si/SiOxpassivated contacts crystalline silicon solar cells. It focuses on thermally-activated Aluminium Oxide (AlOx) layers elaborated by thermal Atomic Layer Deposition (ALD) to passivate the edges of shingled cells cut by using the innovative “45° tilt squaring approach”. The whole procedure featuring high-temperature AlOxannealing led to very low cut-related performance losses. Indeed, the efficiency and FF of the passivated shingled cells surpassed the values obtained for the as-cut shingles by 0.5%absand 2.6%abs, respectively. Approaches for further improvements are also discussed, particularly to overcome the short-circuit current density decrease observed for passivated shingles.

This study focuses on the optimization of the passivation properties of AlOx layers deposited either by ALD. Different thicknesses of AlOx layers have been deposited by ALD on p-type Cz silicon wafers and annealed at different temperatures. In the absence of “SiNx capping”, the increase of the forming gas annealing temperature improves the passivation regardless to the ALD deposited AlOx layer thickness. Very high passivation performances were obtained before SiNx capping (i-Voc around 720 mV) with AlOx ALD deposited layers annealed at 550°C. The deposition of a silicon nitride capping layer remarkably improves the surface passivation (i-Voc gain of 30 to 40 mV) on low temperature annealed AlOx layers but has no influence on the passivation quality of high T annealed AlOx layers. After SiNx capping, i-Voc around 720 mV are obtained regardless to the ALD deposited AlOx thickness and annealing temperature. The same passivation quality is obtained when an AlOx layer is directly covered with a SiNx layer (the AlOx was not annealed before). 33rd European Photovoltaic Solar Energy Conference and Exhibition; 690-693

This work presents the development and the application of innovative and sustainable transparent conductive oxide (TCO) materials for contacting polysilicon (poly-Si) on oxide (SiOx) stacks used as passivating contacts in solar cell devices. Adding hydrogen into ZnO:Al (AZO) layers deposited by magnetron sputtering potentially leads to a twofold positive effect. First, it brings hydrogen atoms into the layers, which can enhance both electrical and optical material properties of the TCO. Second, hydrogen can significantly improve cell performances, by fixing dangling bonds at the SiOx/substrate interface and by passivating bulk defects. In situ and ex situ hydrogenation processes have been compared on those multiple aspects with investigation about anneals at 350 °C. AZO layers have been successfully integrated on the front side of complete solar cells featuring poly-Si/SiOx-based passivating contacts, leading to a record conversion efficiency of 22.4% for a cell with AZO. The results show that using AZO instead of an indium based TCO is suitable for passivated contacts solar cell with high temperature route. Thus, it increases the credibility towards large-scale deployments of TCO-based high efficiency silicon solar cells in terms of cost and resources.

International audience

The SiliconPV 2024 conference brought together nearly 300 scientists and engineers from 27 countries, with 142 abstracts approved by reviewers and presented through 61 oral talks and 71 posters, both onsite and online. 10 submissions were retracted. The conference served as a vibrant platform for exchanging knowledge, sharing ideas, and fostering collaboration among PV experts worldwide. The silicon solar community is witnessing a remarkable period of progress and innovation. Single-junction silicon cells and modules continue to achieve significant advancements, even as they approach the theoretical efficiency limit. In recent months, new benchmarks have been reached for heterojunction and TOPCon devices, with cutting-edge strategies driving further progress. This momentum is even more evident in perovskite-on-silicon tandems, which have now achieved efficiency levels exceeding 34%. Simultaneously, the growth in module production capacities remains robust, positioning the solar manufacturing sector to scale up to the terawatt level – a critical step toward addressing global warming. Bold plans for new gigafactories are taking shape worldwide, highlighting an era of expansion. However, reaching terawatt-scale solar deployment brings its own set of challenges. Beyond manufacturing improvements, the key hurdles lie in ensuring solar technology matures into a fully sustainable industrial sector. These themes – from pioneering concepts in single-junction and tandem cells to sustainable industrial solutions, from advanced silicon materials to high-quality, dependable modules, and from innovative manufacturing techniques to optimizing energy output and costs – were central to the discussions at the SiliconPV 2024 conference held in April, 2024, in Chambéry. We are deeply grateful to the many experts who contributed to reviewing abstracts and full manuscripts, culminating in these valuable proceedings. These proceedings are not just a record of the event; they are a critical resource for the community. By exploring the insights and advancements documented here, we hope you will find inspiration to develop novel technologies that accelerate the energy transition. Together, we can shape a brighter future by ensuring clean and affordable energy is accessible to everyone.

In this study we investigate the coupled impacts of poly-Si thickness, dopant activation annealing temperature and hydrogenation on n-TOPCon and p-TOPCon passivated contacts. Their performance is first assessed by Photoconductance Decay (PCD) measurements on symmetrical and asymmetrical cell precursors before being evaluated on cells by I-V characterizations. We show that high-temperature annealing of poly-Si layers is responsible for excessive dopants penetration in the substrate, which can then be limited by the presence of a thicker poly-Si layer. Moreover, these thicker poly-Si layers benefit more from hydrogenation steps, enabling i-Voc of around 720 mV and carrier lifetimes of up to 5 ms on cell precursors. Finally, while increasing the thickness leads to current limitation under AM1.5G (1 Sun) illumination, this limitation is less pronounced under IR illumination. We therefore demonstrate that for tandem applications, the bottom-cell can benefit from a gain in Voc and FF without suffering from a major optical limitation.