Proposal of high efficiency solar cells with closely stacked InAs/In_(0.48)Ga_(0.52)P quantum dot superlattices: Analysis of polarized absorption characteristics via intermediate-band

摘要

We present a theoretical study of the electronic structures and polarized absorption properties of quantum dot superlattices (QDSLs) using wide-gap matrix material, InAs/In_(0.48)Ga_(0.52)P QDSLs, for realizing intermediate-band solar cells (IBSCs) with two-step photon-absorption. The plane-wave expanded Burt-Foreman operator ordered 8-band k · p theory is used for this calculation, where strain effect and piezoelectric effect are taken into account. We find that the absorption spectra of the second transitions of two-step photon-absorption can be shifted to higher energy region by using In_(0.48)Ga_(0.52)P, which is lattice-matched material to GaAs substrate, as a matrix material instead of GaAs. We also find that the transverse magnetic polarized absorption spectra in InAs/In_(0.48)Ga_(0.52)P QDSL with a separate IB from the rest of the conduction minibands can be shifted to higher energy region by decreasing the QD height. As a result, the second transitions of two-step photon-absorption by the sunlight occur efficiently. These results indicate that InAs/In_(0.48)Ga_(0.52)P QDSLs are suitable material combination of IBSCs toward the realization of ultrahigh efficiency solar cells.