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Researchers at the Los Alamos National Laboratory in the US have developed the first ultrafast photodetector made from quantum dots that is capable of directly observing the extra electrons in a process called "carrier multiplication". This process has the potential to boost the efficiency of solar cells and understanding how it occurs could lead to the development of new types of light and radiation detectors.

 

Dume quantum

 

When a conventional solar cell or photodetector absorbs a photon, a single electron–hole pair called an exciton is created within the device's active semiconductor layer. In nanometre-sized pieces of semiconductor called quantum dots, electrons can interact more strongly with each other after they have absorbed light, and this results in multiple electrons being unleashed by a single photon. This effect is known as carrier multiplication, and it could help to make cheaper and more efficient solar cells as well as new types of detectors.