Hot Carrier Photovoltaic Devices

The concept of a hot carrier solar cell was proposed 40 years ago, promising remarkably high photovoltaic solar power conversion efficiency if the photogenerated carrier population can be decoupled from the phonon population in the absorber material. Some experimental demonstrations of hot-electron photovoltaic devices have been made using molecular, semiconductor and metallic absorbers. In the case of a thin-metallic absorber, almost complete extinction of sunlight can be achieved from a 10nm thick metallic layer. The resulting photocurrent was confirmed to arise from a thermal, hot electron population as opposed to ballistic transport of photogenerated carriers. This distinction is important since a ballistic PV device holds no efficiency benefit over a Shockley Queisser solar cell while a thermal hot-electron population can, in principle, achieve high efficiency.