Energy conversion devices – Foton Institut

Contacts: Olivier Durand (Photovoltaics), Charles Cornet (Solar Hydrogen)

The overall objective of the Photovoltaics research theme is to develop photovoltaic cells based on innovative device concepts, novel materials, and advanced heterostructures. As part of the ecological transition, the FOTON Institute contributes to scientific research aimed at designing and manufacturing solar cells that are either more efficient or more sustainable. As described throughout this section, the OHM Department is actively involved in the development of silicon-based tandem solar cells, as well as other advanced photovoltaic concepts such as hot-carrier solar cells and cells based on metal oxide heterojunctions on Si. Research on solar cells based on halide perovskites is presented separately in the research theme “Perovskite Materials and Device Physics.”

Beyond its activities in photovoltaics, the OHM Department has initiated research on the study and development of novel materials for solar hydrogen production, in collaboration with the ISCR. The direct conversion of light energy into hydrogen, through water electrolysis, would enable the renewable production of a fuel that can be reused on demand to meet our energy needs. The approaches under investigation are based on the use of perovskite materials, as well as III-V semiconductor thin films deposited on silicon substrates, combined with catalysts and corrosion-protection layers. The department is focusing on the development of these materials, their physical properties, their structural and electro-optical characterization, and the photoelectrochemical properties of the developed electrodes.

Results and Highlights

Funded projects

Description of scientific activities

Silicon Tandem Solar Cells: The objective of this research is to develop tandem solar cells combining a monocrystalline silicon bottom cell with a bandgap of 1.1 eV and a top cell with a bandgap of approximately 1.7 eV, enabling efficiencies beyond the theoretical limits of single-junction silicon solar cells. The monolithic integration of CIGS-based heterostructures on silicon offers the possibility of combining high conversion efficiencies with low manufacturing costs, while leveraging established industrial production technologies. The original approach developed within this project consists of introducing an ultra-thin III-V intermediate layer between the silicon cell and the CIGS cell. This layer acts as a selective contact for the CIGS cell, which is grown epitaxially directly on the III-V material. Initial results have demonstrated the epitaxial growth of CIGS on a GaP/Si(001) pseudo-substrate. In addition, the III-V material serves as a chemical barrier between silicon and CIGS, preventing delamination between the two sub-cells. CIGS layers are developed at IMN and IPVF, GaP/Si pseudo-substrates are produced at the FOTON Institute, and silicon solar cells are fabricated at INL.

For further information, please refer to the ANR EPCIS project and the MINOTAURE and IOTA projects of the PEPR TASE program.

Hot-Carrier Solar Cells: Hot-carrier solar cells have the theoretical potential to achieve conversion efficiencies beyond the Shockley–Queisser limit using a single junction. In this type of cell, the goal is to have energy carriers with higher energy than the band gap contribute to the photocurrent before thermalization. This research led to a publication in Nature Energy in 2018. Project partners include IPVF SAS (Palaiseau), UMR IPVF (Palaiseau), C2N (Université Paris-Saclay), IM2NP (Marseille), and LPCNO (Toulouse). Ongoing project: ANR ICEMAN (ANR-19-CE05-0019).

For further information, please refer to the ANR ICEMAN project.

Photovoltaic cells based on metal oxide heterojunctions on Si: High-performance silicon heterojunction solar cells exhibit low surface recombination velocities thanks to a wide-bandgap emitter layer that allows majority carriers to flow toward the electrical contact while reflecting minority carriers. This layer is typically made of an amorphous a-Si:H layer (1.7 eV quasi-bandgap), which has high optical losses, limiting light conversion to short wavelengths. Molybdenum oxide (MoO₃) is a promising alternative to a-Si:H because of its wider bandgap (2.9 eV) and high work function, which enable favorable electronic band alignment between the emitter layer and the silicon absorber. This research is conducted within the framework of the European NANO-EH project, which focuses on the development of autonomous systems for the Internet of Things (IoT). The project aims to optimize novel low-cost and non-toxic nanomaterials for integration into miniaturized energy harvesting and storage devices, including rectennas, pyroelectric devices, supercapacitors, and photovoltaic systems. The broader context of the NANO-EH project lies in the advancement of communication technologies and IoT applications in areas such as personalized medicine, smart agriculture, and environmental monitoring.

For further information, please refer to the H2020 FET Proactive Nano-EH project.