esearchers in China have created a transparent, colorless, and unidirectional solar concentrator that can be directly coated onto standard window glass and used to harvest sunlight without changing the window’s appearance.
The innovation, which was designed by a research team at Nanjing University in the Chinese province of Jiangsu, uses cholesteric liquid crystal (CLC) multilayers with submicron lateral periodicities.
According to the scientists, this unique diffractive-type solar concentrator (CUSC) selectively guides sunlight toward the edge of the window where photovoltaic (PV) cells are installed.
“By engineering the structure of cholesteric liquid crystal films, we create a system that selectively diffracts circularly polarized light, guiding it into the glass waveguide at steep angles,” Dewei Zhang, PhD, a researcher at Nanjing University and first author of the study, disclosed.
Efficient energy harvesting
Unlike conventional luminescent or scattering-based concentrators, which often suffer from visual distortion, low efficiency, and poor scalability, the new CUSC delivers broadband, polarization-selective diffraction and efficient waveguiding while preserving complete visual clarity.
Zhang revealed that the device achieves a high average visible transmittance of around 64.2 percent and a color rendering index of 91.3 percent. “This allows up to 38.1 percent of incident green light energy to be collected at the edge,” the scientist explained.
These optical qualities mean the coating can generate clean energy while keeping the glass clear and natural-looking, and ensure that windows remain visually indistinguishable from ordinary glass.
The team also highlighted the system’s impressive scalability. Simulations showed that a standard 6.5-foot-wide (two-meter-wide) CUSC window could concentrate sunlight up to 50 times its normal intensity and thus significantly enhance its energy-gathering potential.
This level of performance would allow for a reduction of up to 75 percent in the photovoltaic cell area required, slash material costs, and open the door to new design possibilities for energy-efficient buildings.
Future development goals
Experiments conducted by the team showed that a one-inch-diameter prototype could directly power a 10-milliwatt (mW) fan outdoors under sunlight. The system is also compatible with high-performance photovoltaic cells, like gallium arsenide (GaAs), a compound semiconductor that boosts overall power conversion.
“The CUSC design is a step forward in integrating solar technology into the built environment without sacrificing aesthetics,” Wei Hu, PhD, a computer science and technology professor at Nanjing University and corresponding author, said.
Hu said that the multilayered CLC films are fabricated using photoalignment and polymerization techniques and can be scaled through roll-to-roll manufacturing. “It represents a practical and scalable strategy for carbon reduction and energy self-sufficiency,” he concluded in a press release.
In addition, the design shows long-term stability under prolonged environmental exposure and can be seamlessly retrofitted onto existing window structures. This makes it a practical solution for large-scale, sustainable urban upgrades.
The team plans to improve the technology’s broadband efficiency and polarization control. They are also exploringapplications beyond buildings, including agricultural greenhouses and transparent solar displays.
