In solar cells, solar radiation boosts electrons to higher energy states, thereby releasing them from their atomic bonds as electricity begins to flow. Scientists led by Professor Alexander Holleitner, physicist at the Technische Universität Muenchen (TUM), have developed a novel method to analyze the way photogenerated electrons move in the smallest photodetectors. They present the fruits of their research in the current issue of Nano Letters.

At the heart of the method is a so-called quantum point contact (QPC). This is a narrow conductive channel in a semiconductor circuit. The scientists created a 70-nanometer narrow channel, about as wide as the wavelength of electrons in the semiconductor. The key is that only one electron at a time will fit through the channel, making possible extremely high-precision measurements of the electric current. As described in the current publication, this method was applied to photogenerated electrons for the first time ever.

 Read the complete press release (TUM)