In the quest for energy independence, researchers have studied solar thermoelectric generators (STEGs) as a promising source of solar electricity generation. Unlike the photovoltaics currently used in most solar panels, STEGs can harness all kinds of thermal energy in addition to sunlight. The simple devices have hot and cold sides with semiconductor materials in between, and the difference in temperature between the sides generates electricity through a physical phenomenon known as the Seebeck effect.

But current STEGs have major efficiency limitations preventing them from being more widely adopted as a practical form of energy production. Right now, most solar thermoelectric generators convert less than 1% of sunlight into electricity, compared to roughly 20% for residential solar panel systems.

That gap in efficiency has been dramatically reduced through new techniques developed by researchers at the University of Rochester’s Institute of Optics.

An international team led by UCL researchers has developed durable new solar cells capable of efficiently harvesting energy from indoor light, meaning that devices such as keyboards, remote controls, alarms and sensors could soon be battery-free.

The team used a material called perovskite, which is increasingly used in outdoor solar panels, and unlike traditional silicon-based solar panels, has the potential to be used indoors as well as its composition can be adjusted to better absorb the specific wavelengths of indoor light.

A major drawback of perovskite, however, is that it contains tiny defects in its crystal structure —known as traps—that can cause electrons to get stuck before their energy can be harnessed. These defects not only interrupt the flow of electricity but also contribute to the material’s degradation over time.