AlGaInAs Quantum Dots for Intermediate Band Formation in Solar Cell Devices

Abstract

In this chapter, we focus on the integration of composition tailored AlGaInAs quantum dots (QDs) into AlGaAs p–i–n diode structures for solar cell (SC) applications. This type of QDs can absorb a wide range of the solar spectrum from the red visible to the near infrared spectral range. Moreover, the size, density, and eigenenergies of these quaternary QDs can be easily adjusted via varying their material composition, e.g. the aluminum content. We anticipate that the suitable choice of material composition, dot shape, and inter-dot barrier thickness can compensate the built-in potential of the p-i-n junction and electronic coupling between QD layers will be established to generate an electronically isolated intermediate band (IB). In order to probe the operation principle of an IBSC utilizing AlGaInAs QDs, two photon absorption measurements were performed. We show that two sub-bandgap photons produce photocurrent while the first photon pumps electrons from the valence band (VB) to the IB and a second photon lifts the electrons from the IB to the conduction band (CB). Based on our result we propose a route towards intermediate band solar cells (IBSCs) with these quaternary QDs.