Solar windows that generate electricity with artificial light: the advance that could transform buildings

An international research team, led by University College London (UCL), has created semitransparent solar windows capable of harvesting energy from both sunlight and artificial indoor lighting. This breakthrough, detailed in the journal Advanced Energy Materials, offers the potential to turn buildings into clean energy producers around the clock.

The developed windows allow approximately 30% of sunlight to pass through, compared to the 80-90% of common glass, while efficiently converting a record amount of indoor light into electricity. The design also mimics tinted glass by reducing heat entering buildings, which could lower the need for air conditioning.

Dr. Mojtaba Abdi-Jalebi, senior author from UCL's Institute for Materials Discovery, highlighted the untapped potential of building facades: "Roofs are often equipped with solar panels, but the vast glazed surfaces of many modern buildings remain largely unutilized as an energy resource."

The key innovation lies in the use of perovskite, a material increasingly found in conventional solar panels. Unlike traditional silicon, perovskite's composition can be tailored to absorb specific wavelengths of artificial light, making it suitable for indoor energy generation. The researchers optimized the perovskite layer to be extremely thin, just 185 nanometers, to maintain transparency without sacrificing efficiency.

To address material defects that hinder electron energy release, a specific molecule was incorporated, which also stabilized the perovskite's crystal structure and slowed degradation. A significant technical challenge was overcome by designing a transparent electrode using a thin gold layer sandwiched between molybdenum oxide layers, allowing light to pass through while conducting electricity. Laboratory tests on a 30x30 cm panel showed the cells converted 22% of intense artificial light and 14% of sunlight into electricity, retaining 80% of their efficiency after accelerated durability tests.

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Roofs are often equipped with solar panels, but the vast glazed surfaces of many modern buildings remain largely unutilized as an energy resource.