Hybrid perovskite solar cell integrated with an electrolyser. Perovskite is a material that has the same crystal structure as calcium titanium oxide. The solar cell converts the energy from light into electrical energy. The electric currents generated are used by the electrolyser. This allows for the electrolysis of water, splitting water into hydrogen and oxygen. The hydrogen (small bubbles) produced can be used as a fuel. Perovskite solar cells are more efficient than silicon solar cells. Photographed at the National Renewable Energy Laboratory, Golden, Colorado, USA.