Japanese scientists say they have developed a platinum-based application capable of converting solar energy into an electrical charge that can be stored.

Tsutomu Miyasaka and Takurou Murakami at Toin University in Yokohama say that the ability to store the charge could prove useful for powering mobile phones and other hand-held devices.

The device is, essentially, two electrodes separated by a resin film. One electrode is a light-absorbing titanium photoelectrode, with the other made of platinum coated glass.

Each electrode has a porous layer of activated carbon, which is filled with an ionic solution.

The result is a capacitor with a 0.64 square centimetres light-sensitive area, with photoreceptor dye molecules on the surface of the titanium dioxide layer collecting photons.

These dye molecules then react to light, with electrons transferred to the conducting band in the titanium dioxide layer, thus producing a current.

Miyasaka told PhysicsWeb that the photocapacitor is "twice as efficient as traditional silicon-based solar cells in utilising weak light".

"This means that it can utilise indirect sunlight, for example on cloudy or rainy days, and even indoor light. Moreover, it can release electrical energy anytime, even in the dark."

Now the team are seeking to increase the charging voltage and the charge-discharge capacity to an industrial level.