Windows with a transparent solar coating over them could soon revolutionize energy efficiency and power generation in cities across the world. According to the World Economic Forum, the coating is made by California-based Ubiquitous Energy and can be added to standard windows while they’re being made, effectively turning them into solar panels. The coating contains special organic salts, which absorb a non-visible portion of the solar spectrum while letting visible light pass through to illuminate the room.
Ubiquitous Energy has stated that if deployed on a large scale, ‘solar windows’ could transform solar capacity worldwide turning every building in the world into a solar generator, and skyscrapers into solar powerhouses. Michigan State University has installed solar windows in its Biomedical Sciences Building. They will provide enough energy to power the building’s atrium.
The same coating could also be applied to the screens of smartphones, e-readers and laptops to power the devices. To reach the world’s climate goals, solar and wind power should contribute 70% of global energy by 2050
Researchers at the École Polytechnique Fédérale de Lausanne (EPFL) have discovered a way to create transparent photosensitizers, molecules that can be activated by light and adsorb light across the entire visible light spectrum, as reported by Euronews. Previous versions of mesoscopic dye-sensitized solar cells (DSCs) relied heavily on direct sunlight.
Our findings offer promising prospects for power supply and battery replacement applications for low-power electronic devices.
Scientists at the EPFL
The transparent solar cells can be made translucent, bendable and multi-colored for a reasonable price. Skylights, greenhouses and glazed facades already use these transparent solar panels. The SwissTech Convention Center was the first public facility to use DSC’s technology in 2012.
According to researchers in Grätzel’s and Anders Hagfeldt’s groups at EPFL, the packaging of two newly created photosensitizer dye molecules can now be improved to enhance the photovoltaic performance of the DSC.
The new photo-sensitizers can quantitatively collect light across the entire visible spectrum when used together. The novel method involves pre-adsorbing a monolayer of a hydroxamic acid derivative onto the mesoporous nanocrystalline surface of titanium dioxide. This slows the adsorption of the two sensitizers, allowing a layer of sensitizer to grow on the titanium dioxide surface that is well ordered and densely packed.
The method produces DSC with two or more distinct dyes that exhibit complementary optical absorption. It is a chemical manufacturing process. Co-sensitization can be used to combine dyes capable of absorbing light from the entire light spectrum, so it has boosted the power conversion efficiencies of DSCs to unprecedented levels. Co-sensitization has, however, sometimes proven inefficient due to the laborious molecular design, synthesis and screening required to identify the ideal dye.
“Our findings pave the way for easy access to high-performance DSCs and offer promising prospects for power supply and battery replacement applications for low-power electronic devices that use ambient light as a source of energy,” the EPFL scientists explain in the press release.
Using this method, the team succeeded in creating DSCs with an energy conversion efficiency of 15.2% for the first time under typical simulated sunlight worldwide, after testing their long-term operational stability for 500 hours. The energy conversion efficiency ranged from 28.4 to 30.2% over a wide range of ambient light intensities, with exceptional stability when expanding the active surface area to 2.8 cm2.
Meanwhile, a team based at Monash University and Australia’s national science agency CSIRO working with solar cells made from perovskite materials, found that a combination of caesium and formamidinium in the initial perovskite composition delivered the best performance over different band gaps (a band gap is the minimum energy that is harnessed for delivering power from the sun). Perovskite materials can be readily created in a laboratory and tuned to suit different purposes, including the type of energy they conduct and how much light they absorb, reflect and transmit.
The cells demonstrated excellent long-term stability when tested for continuous illumination and heating, which mimics the conditions the devices would encounter in real-world use, retaining 85% of their initial power conversion efficiency after 1,000 hours of continuous light.
Researchers have now demonstrated power conversion efficiencies of 15.5% and 4.1% for different types of prototype semi-transparent solar cells, with visible transmittance of 20.7% and 52.4% respectively. While the power-conversion efficiencies are lower than their previous results, the amount of visible light these new materials allow to pass through is significantly greater, increasing their potential to be used in a wide range of real-world applications.
