Growth, Fabrication and Characterization of Quantum Dot Intermediate Band Solar Cell

Abstract

Stacked layers of self-assembled InAs quantum dots were synthesized within the base region close to the back surface field of GaAs single junction n- on p-solar cell. The solar cell structure was grown epitaxially on p-type GaAs substrate by using molecular beam epitaxy technique. Quantum dot layers with 15 periods were grown by growing 2.7 monolayers (ML) of InAs and each layer were capped with 25 nm GaAs. Except InAs/GaAs intermediate band layers which were grown at a substrate temperature of 490 degrees C, solar cell structure was grown at 580 degrees C. For comparison, a reference structure was also grown without InAs quantum dots. Solar cell devices were fabricated and measured under AM 1.5G solar spectrum to evaluate and compare opto-electronic performances of each structure. Corroborative photo luminescence measurements were also performed to draw out the effects of InAs quantum dots in the optical performance of cells. Extracted parameters of solar cells from the current-voltage measurements revealed that, the quantum dot intermediate band solar cell exhibits better performance compare to the reference one. For both cell structures shunt resistances are same, which indicates that the difference in efficiency is due to the intrinsic property of devices other than fabrication processes.