Affordable TAndem Cell Architecture by Multi-thin-epitaxy Approach

Climate change is one of the greatest challenges of our time. It is essential to drastically reduce greenhouse gas emissions. We need more and better photovoltacis (PV) to drastically reduce the CO2 emissions.

PV will need to be widely distributed to be able to replace the enormous (and growing) amounts of conventional electrical energy.

Availability of surface areas allocated to PV, preferably close to the end use of the electricity, will become an issue. Reliability and a high energy yield per area will become important for the success of PV products. Europe presents higher complexity than other regions, because of its limited space and high-density population.

Current Silicon technology is basically limited by its single junction (one semiconductor bandgap) to efficiencies below 30%.

Multi-junctions/Tandems using more than one semiconductor diode (aiming at different energies in the spectrum) are the demonstrated path to overpass this limit and achieve efficiencies close to 40%, as done for three junctions (3J) on III-V and with 35% achievable by using a Si bottom junction (3J GaInP/GaAs/Si).

Two tandems technologies have emerged as promising to upgrade the current Si technology: perovskites/Si and III-V/Si. III-V/Si presents the highest efficiency and stability (20-30years) but two orders of magnitude higher cost.

The ATACAMA project will develop the top junction for a III-V/Si tandem (AlGaAs/Si), with a drastic reduction in cost for the III-Vs by (1) ultra-thin absorbers using low-cost nanostructuring and (2) substrate multi-thin-epitaxial enable by a novel epitaxial lift-off process. Furthermore, the III-V/Si tandem has to attain a high efficiency (>30%)(3), that will ensure a cost-effective solution.

Nevertheless, the tandem must ensure circularity (recyclable path) to split the Si from the III-V, by gluing with transparent polymers, with a melting point of 200°C, ensuring the possibility of easily recycling in the future the AlGaAs cell from the Si cell.