High-Efficiency, Radiation-Hard, Lightweight IMM Solar Cells

Future NASA exploration missions require high specific power (>500 W/kg) solar arrays. To increase cell efficiency while reducing weight and maintaining structural integrity, we propose an approach to cell design that involves the use of quantum dots and epitaxial lift-off. In the near term, this approach will allow us to improve on what are currently the best space solar cells available in terms of efficiency and material properties for space utilization. In the proposed Phase I project, MicroLink and its collaborator, Rochester Institute of Technology, will incorporate InAs quantum dots (QDs) in the InGaAs subcell of an InGaP/GaAs/InGaAs triple-junction solar cell to increase radiation tolerance and efficiency, thereby improving end-of-life performance of the solar cell by >5%. By incorporating quantum dots into the InGaAs third cell, we will also extend the wavelength absorption range of InGaAs cell to beyond 1,250 nm, thereby increasing the current produced in the bottom subcell. The quantum dot-enhanced subcell will be the last grown solar cell in an inverted metamorphic (IMM) format on GaAs and will be compatible with MicroLink's epitaxial lift-off (ELO) process. Innovative light management techniques such as reflective metal back contact will be employed to increase absorption in the solar cell by promoting photon recycling.