Temperature dependent photoluminescence spectroscopy of InAs/GaAs solar cells

The InAs/GaAs quantum dot system has been shown to improve device performance when included in single junction GaAs solar cells. The management of electrons and holes in the barrier material, well material and between the two is important for the successful function of such nanostructured devices. Since carriers produced in these confined materials can only be collected if they are extracted to the conduction band, it is of interest to investigate the energy needed, or the activation energy of the wells. Extraction is strongly aided by phonon interaction and is therefore a temperature dependent process. Here, temperature dependent spectroscopy experiments are performed on both test structures and solar cells and are used in the study of thermal influence on device performance as well as carrier dynamics. Relatively temperature insensitive sub bandgap conversion is shown and activation energies ranging from 38meV to 400meV are determined and their meaning analyzed. Improvements to InAs/GaAs solar cells are suggested from the information.