A photovoltaic device that converts sunlight into heat to generate power has achieved greater efficiency than previous such devices, thanks to the design of nanomaterials in the light-absorbing layer.

Thermophotovoltaics contain a layer that absorbs a wider spectrum of wavelengths than conventional solar cells. This layer radiates heat that is used to generate electricity. Evelyn Wang and her team at the Massachusetts Institute of Technology in Cambridge designed their absorber–emitter material by growing an array of carbon nanotubes, which turn light into heat, onto a layer of photonic crystals, which they engineered to emit energy of the optimum levels for power generation.

The researchers' device reached an energy conversion efficiency of 3.2%, three times greater than in previous experiments. The authors say that with further improvements, efficiency could exceed 20%.

Nature Nanotech. http://doi.org/q6j (2014)