Researchers at Northwestern University have now found a way to tweak an important electrical feature of transition metal oxides, compounds commonly used as semiconductors, to build the optimal light-absorbing material for solar cells, lasers and photoelectrochemical cells.

In electronics, the band gap is a crucial feature of a semiconductor, measuring the amount of energy that an electron needs to be fed before it can start conducting electricity. Its size is measured in electronvolts (eV) and dictates whether a material will behave as a conductor (~0 eV), a semiconductor (~1–9 eV) or an insulator (~9 or more eV).

Being able to tweak the band gap at will would be incredibly useful. Solar cells, for instance, produce electricity whenever a photon travels to a silicon atom and "hits" it, giving one of silicon's electrons enough energy to jump the band gap and become conductive. Tuning the band gap would mean being able to design the ideal semiconductor that can maximize the amount of energy harvested throughout the visible spectrum.