(Invited) Potential and Activities of III-V/Si Tandem Solar Cells

Abstract

The paper presents efficiency potential of III-V/Si tandem solar cells with efficiencies of more than 35% under 1-sun AM1.5G and effects of dislocation upon solar cell properties of III-V-on-Si single-junction solar cells and III-V/Si tandem solar cells. Because III-V/Si system has large lattice mismatching and difference in thermal expansion coefficient, generation of misfit and thermal stress induced dislocations affect on solar cell properties. Effects of dislocations upon minority-carrier lifetime are derived from considering one dimensional transport of minority carriers to dislocations. In order to realize high efficiency solar cells with similar efficiency by homo-epitaxially grown solar cells, low density dislocation of less than 3x105 cm-2 is necessary. This paper also reviews approaches on reduction in dislocation density in III-V compound films on Si and improvements in efficiencies of III-V compound single-junction solar cells on Si substrates and III-V/Si tandem solar cells.

Current and efficiency improvement for a GaAsP/SiGe on Si tandem solar cell device achieved by light trapping techniques

“…However, the challenge is the lattice mismatch between epitaxially grown III–V materials and Si. Many researchers have developed a variety of techniques to lower the threading dislocation density (TDD) . Compared to other techniques, Si x Ge 1– x buffer layers have led to the lowest TDD in the III–V layers and subsequently maintained the high open‐circuit voltage ( V oc ) for the III–V stacks.…”