By using UV photoelectron spectroscopy and optical absorption measurements, the researchers determined the energy of the lowest excited electronic states in the nanocrystals.

It's called this just because it's an electron that results when an electron absorbs a photon's worth of energy, so thus it's a photoelectron.

Based on the study of X-ray photoelectron spectroscopy of lead glass, it is found that the binding energy peaks of oxygen and silicon slightly shifted after implantation.