Type-II Ge/Si Quantum Dot superlattice for Intermediate-band Solar Cell Applications

Abstract

A Ge/Si type-II quantum dot (QD) has been developed for use in all-Si intermediate-band solar cell (IBSC) applications. A top-down process is used to fabricate the ultra-high-quality QD superlattice. A newly developed 3D finite element method was used to solve several key design problems in achieving a practical structure. Theoretical calculations revealed that a heavy hole state can act as an ideal intermediate band when the interdot space ranges from 0.5 to 4 nm. An IBSC based on this superlattice dramatically enhanced conversion efficiency for concentration applications. For one-sun applications, H-passivizing Si and/or regrowthing amorphous SiC have a great potential to improve the conversion efficiency.