The building sector accounts for about 40% of total energy consumption in developed countries, and about half of the energy is used for heating, ventilation and air-conditioning systems. Windows represent a major source of heat gain or loss, as well as visual and thermal discomfort, but they are regarded as the least energy-efficient sector of buildings. Smart windows can selectively regulate excess solar radiation to reduce heating and cooling energy consumption in the built environment, but the inevitable dissipation of ultraviolet and near-infrared rays into waste heat results in inefficient solar utilization.

Therefore, in this project, we developed a dual-band selective solar harvesting (SSH) window for full-spectrum utilization. A transparent photovoltaic device that converts ultraviolet rays into electricity, and a transparent solar absorber that converts near-infrared into thermal energy are integrated and coupled with a ventilation system to extract heat for indoor use. Compared to common transparent photovoltaics, the SSH window increases solar harvesting efficiency up to threefold while maintaining a considerable visible transmittance. Simulations suggest that in addition to generating electricity, the SSH windows deliver more than 30% more energy savings than common smart windows.

This is the first integration of transparent photovoltaic and transparent solar absorbers into a window, which may open up a new avenue for the development of energy-efficient buildings.