Researchers at the Institute of Solar Energy of the Polytechnic University of Madrid manufacture micro-prototypes of ultra-thin solar cells with various materials that promote the absorption of solar energy on any surface.

Every hour, the Earth receives an amount of energy from the Sun comparable to the world's annual energy consumption. The development of two-dimensional materials will make it possible to use any surface to absorb this energy. For some years now, much thinner and lighter materials capable of absorbing solar energy have been studied [1]. These are two-dimensional photovoltaic materials, so thin that they are not considered to have a third dimension, yet they can absorb a surprising amount of light.

The Silicon and New Concepts for Solar Cells research group (Sync) of the Solar Energy Institute (IES) of the Polytechnic University of Madrid (UPM[Name of researcher] has carried out work to join two-dimensional materials and obtain highly efficient solar cells. This was achieved using a technique called hot-pick-up, In this process, fragments of materials are selected, collected, and deposited within a transparent bubble, forming stacks tailored to the research needs. The versatility of the process has allowed for experimentation with different materials, which, by combining their unique properties, enable optimal absorption of solar energy. Through this manufacturing technique, the SYNC group has achieved efficiencies that place UPM among the leading universities in this technology.

We live in a society that consumes ever more energy and lives in larger, denser cities. Within the renewable energy sector, current photovoltaic technology faces challenges from this urban growth due to factors such as its weight, size, and rigidity, which hinder its integration into cities. In this context, researchers at IES-UPM are working with new techniques to scale up the solar cell manufacturing process by depositing two-dimensional materials from solution over large areas. "Using spraying and deposition techniques for these solutions, manufacturing processes could be scaled up, reducing costs and enabling the industrialization of this disruptive photovoltaic technology," the researchers explain.

In parallel, the real impact of integrating this technology into cities has been studied. Simulating the effects of cladding a Madrid skyscraper with these semi-transparent materials, it has been estimated that up to 301,000 tons of the building's energy consumption could be generated while maintaining pleasant lighting in the offices inside [2]. The lightness, flexibility, and low manufacturing cost of these solar cells make them one of the most promising options for achieving green cities based on clean energy, where any surface can be a source of energy.

The authors gratefully acknowledge the financial support of the MAD2DCM-UPM project, funded by the Community of Madrid and the European Union; the support granted by 4EVERPV-CM from the Community of Madrid; the support of the COMIC and PVBooster grants from the Ministry of Science and Innovation; and the APE2SOL award from the Naturgy Foundation.