The new device will be cheaper to make because it uses less expensive semiconductor materials than conventional solar cells. German physicists Rolf Könenkamp, Katja Ernst, and Abdelhak Belaidi have used a layer of titanium dioxide full of tiny pores to make a more efficient device. They then formed an extremely thin layer of the light-sensitive cadmium telluride (CdTe), which forms the material for the solar cell, on top of the porous titanium dioxide, which was itself supported on a sheet of glass. A dense array of electrical contacts was attached to the back of this sandwich. When sunlight hits the cadmium telluride layer, the electrical current created is tapped off via the electrical contacts. Any stray light bounces around inside the tiny pores in the titanium dioxide layer and is scattered back into the cadmium telluride layer, boosting efficiency by a factor of fifty compared to a similar cell based on a non-porous support material.
The prototype solar cell produces a voltage of 0.67V and a current of 8.9mA/cm2. The researchers also found that if they alloyed the CdTe with mercury, they could boost the current up to 15mA/cm2.
