The integration of solar energy into urban architecture is entering a new phase thanks to the development of advanced photovoltaic coatings and spray-on solutions. So-called “solar paint” is a prime example of the emerging technologies driving new energy solutions.
Through nanotechnology and the chemical synthesis of crystalline compounds, energy-sector research is making progress toward turning everyday surfaces, from façades and walls to roofs and vehicles, into renewable energy harvesters without altering their design.
Although it is still an emerging technology with no commercial product yet on the market, laboratory progress with ultra-thin layers and solution-processable solar cells is opening a promising path toward transforming the distributed generation model without taking up additional land or relying on large, rigid infrastructure.
The key to this leap forward lies in compounds with a perovskite structure. Although the original mineral was identified in the 19th century, its artificial synthesis for use in solar cells is a 21st-century development that began in 2009 with initial efficiencies of just 3%. Thanks to their remarkable optoelectronic properties (for example, outstanding light absorption at minimal thicknesses and a high capacity to convert light into mobile electrical charges), laboratory developments have far exceeded 20% conversion efficiency and make it possible to formulate liquid solutions or inks that can be deposited as thin films on almost any substrate.
This versatility stands in contrast to traditional crystalline silicon solar panels, opening the door for building elements and envelope surfaces to generate electricity in an integrated way.
Ultra-thin coatings and spray-on solar cells
Along these lines, researchers at the Department of Physics at the University of Oxford have achieved an efficiency of over 27% in perovskite-based devices processed as coatings. This performance surpasses the typical 22% average of commercial silicon panels. The breakthrough is based on a multilayer structure (multijunction) just over one micron thick, nearly 150 times thinner than a conventional silicon wafer, capable of absorbing different portions of the solar spectrum. As Dr. Junke Wang, a researcher at Oxford, explained, these materials match and outperform silicon while offering flexibility, paving the way for direct applications on car roofs, building façades, and electronic devices.
Scientists at the Faculty of Mathematical and Physical Sciences of the University of Sheffield in the UK are working on the Enduring Flight program, which aims to spray perovskite solar cells directly onto carbon fiber surfaces to create a “solar skin”. These sprayed cells, made from earth-abundant materials and processed at substantially lower temperatures than silicon, offer a power-to-weight ratio up to 30 times higher than that of traditional photovoltaic panels.
Despite these encouraging figures, experts point out that there is still no commercial “solar paint” for residential use. Generating energy requires a circuit to collect and extract the generated current (power take-off), so simply applying a coat of paint to an ordinary wall is not enough to produce usable electricity. In addition, durability is the main technical challenge: because they are lab-synthesized crystals, perovskites require specific treatments to withstand exposure to air, moisture, and other environmental factors without degrading.
For this reason, the most advanced lines of research focus on developing protected ultra-thin coatings, sprayable solar cells (spray-on), and weather- and corrosion-resistant formulations using advanced encapsulation.
The road to durability and efficiency
The University of Sheffield team is working with Loughborough University and the Advanced Manufacturing Research Centre (AMRC) to design multilayer protective films based on polymers and ultra-thin glass that act as a watertight barrier against the elements without adding weight.
As a preliminary step toward mass commercialization, tandem technology, which combines the stability of silicon with thin perovskite layers, is already reaching pre-commercial manufacturing stages. A British company spun out of the University of Oxford has certified efficiencies of 26.9% in tandem modules designed for residential rooftops and produced at its plant in Brandenburg, Germany, demonstrating the industrial viability of these materials ahead of their eventual consolidation as direct-application inks or coatings.
The convergence of nanomaterials and energy-efficient construction points to a future in which cities manage energy more efficiently, even actively capturing it through their own surfaces. If research into durability and continuous application methods pays off, photovoltaic coatings will make it possible to multiply installed renewable capacity and advance toward an energy transition in which every façade contributes to the balance of the system.
These advances contribute to the relentless race for efficiency: in just ten years, between 2010 and 2019, the cost of generating electricity from solar photovoltaics fell by more than 80%. And while there is still a way to go, a commitment to innovation is making it possible to increase the supply of renewable energy and continue driving the energy transition.
