A dye that creates iris-like crystals makes it easier to convert skyscrapers and greenhouses into power plants.

The sense of sight has inspired numerous technological advances, from sensor design to the development of cameras capable of discerning relevant information for decision-making with reduced information and energy consumption. Now, the iris' ability to adapt to different lighting conditions has inspired an international group of 24 researchers from six institutions to develop a photochromic tint capable of regulating, without external devices, the light required by, for example, a photovoltaic panel. This breakthrough, published in Nature and honored with an international award from the Royal Society of Chemistry , would make it possible to convert a glass-enclosed skyscraper or a greenhouse into monumental energy generators without altering the living conditions and functioning of the interior.

The breakthrough arises, as the researchers explain in Nature , from a limitation that affects the use of solar energy: the manufacture of solar cells with a fixed optical transmission. This means that either the light conditions are not fully utilized throughout the day or external orientation devices must be used to find the best orientation for each hour, something difficult to implement in fixed structures, such as buildings.

The Nanomaterials and Energy Conversion Devices group at Pablo de Olavide University (Seville), led by Professor Juan Antonio Anta, joined the international PISCO team to bridge this gap. The goal is to develop photochromic dyes that, when applied to semitransparent solar cells, are capable of adapting to lighting conditions, maintaining maximum transparency in low light conditions and darkening when exposed to full radiation.

"This work demonstrates the feasibility of combining two often difficult-to-reconcile functions—photochromism and photovoltaics—within a single device and using a single molecule. It represents an important step toward dynamic, energy-generating windows for the next generation of buildings and infrastructure," the Royal Society of Chemistry emphasizes.

According to Anta, the photochromic dye "is a molecule capable of changing color depending on the light, so that it can be incorporated into semi-transparent solar cells that can be used in smart windows."

“The idea,” he adds, “is to incorporate photovoltaic panels into buildings. To incorporate a solar cell into a window, you need it to be semi-transparent and also have to be smart, meaning it darkens during the day while producing electricity. Another application we're also currently exploring is in greenhouses, where they would have a dual purpose: generating energy and protecting the plants.”

One of the limitations of current systems is the instability of the materials. Photovoltaic generation, although it may seem paradoxical, is lower during the summer due to the heat. This reduces the effectiveness of silicon, the most common element in current panels. This loss is partly offset by the greater number of daylight hours, but photovoltaic energy is important for moderate radiation.

Temperature, not just radiation, is important, so the technique developed by the PISCO group, based on organic dyes, also seeks a formula that makes it more stable and robust, as well as more responsive to changes in lighting conditions.

The main objective is to ensure thermal stability inside buildings without compromising energy generation capacity. The molecules researched for the innovative dye are inspired by the eye, as they are the ones that best respond to light.

The UPO team, in addition to Juan Antonio Anta , includes Professor Gerko Oskam, postdoctoral fellows Renán Escalante and Valid Mwalukuku, and predoctoral student Patricia Sánchez Fernández. Anta's team focuses on the study of energy photoconversion processes, optoelectronics, and simulation in solar cells, but also applies research to novel materials for solar hydrogen generation.

“This technology has the potential to make a significant contribution to transforming passive windows into active solar cells. For window applications, both transparency and the ability to provide shade when needed are key features, and this approach can achieve both while generating energy,” explains Johan Liotier, a chemist at the University of Freiburg and a member of the team.

In the field of solar energy, researcher Eduardo Fernández Camacho, professor in the Department of Systems Engineering and Automation at the University of Seville, has also been awarded a grant from the European Research Council (ERC) for the Cooperative Optimal Control of Solar Plants project. The main objective of this research is to demonstrate that Multi-Scenario Cooperative Model Predictive Control (MSC-MPC) algorithms can be effectively applied to optimize the production of commercial solar plants. The main idea is the coordination of the different subsystems of a plant to optimize production over a multi-day horizon, taking into account uncertainties in environmental and market conditions.