Researchers at Hong Kong Polytechnic University have achieved a record light utilisation efficiency (LUE) of 6.05% with semi-transparent organic photovoltaics (ST-OPVs). This milestone brings energy-generating windows a step closer to widespread use in architecture and product design.

A breakthrough for solar glazing

The study, published in Nature Communications, introduces a new assessment method called FoMLUE – short for Figure of Merit for Light Utilisation Efficiency. This parameter evaluates how well photovoltaic materials balance transparency, bandgap, and current density. It allows researchers to quickly identify material combinations that optimise both clarity and power generation, a crucial balance for solar glass applications.

Using this approach, the team developed a new organic photovoltaic blend that, combined with an ultrathin silver electrode and an aperiodic band-pass filter (ABPF), reached the record efficiency while maintaining around 50% visible transparency. The glazing offers excellent colour rendering and a neutral appearance, important for architectural and interior applications where natural daylight quality matters.

Energy savings and thermal comfort

In addition to its efficiency, the new glazing improves thermal control. The ABPF layer reflects infrared radiation while letting visible light through, reducing unwanted heat gain without darkening the glass. Tests showed that the cells remained stable during prolonged operation, with a lifetime exceeding 800 hours under continuous illumination.

Computer simulations across 371 Chinese cities revealed that buildings using these solar windows could achieve annual energy savings of up to 1.43 GJ per square metre. The best results occurred in hot-summer, mild-winter climates, where the material’s ability to block heat provides the greatest benefits.

Applications in design and architecture

For architects and interior designers, this technology opens the door to façades, skylights, and partitions that generate electricity without compromising daylight quality. The thin-film structure can be integrated into double-glazed units, making it suitable for both new buildings and retrofits.

Product designers could apply the same concept in transparent panels or smart devices that harvest energy from ambient light. Landscape architects might also use ST-OPVs in greenhouses, where controlling heat and light levels is crucial for plant growth.

Towards sustainable building envelopes

Because these organic solar cells can be manufactured using low-temperature, solution-based processes, they offer a more energy-efficient alternative to conventional silicon PV. The combination of renewable energy generation, daylighting, and thermal comfort supports a move towards carbon-neutral building envelopes and a more circular construction sector.

Source: TW.nl
Photo: Kindel Media