Performance assessment of a triple-junction solar cell with 1.0 eV GaAsBi absorber

Area of Science:

• Materials Science
• Semiconductor Physics
• Photovoltaics

Background:

• Group III-V multi-junction solar cells offer high efficiency and radiation hardness for space and concentrated solar power.
• Current technologies like GaInP/InGaAs/Ge are mature, but new architectures seek improved bandgap combinations.
• Replacing Germanium (Ge) with a 1.0 eV subcell is a key strategy for efficiency enhancement.

Purpose of the Study:

• To present a novel thin-film triple-junction solar cell incorporating a 1.0 eV dilute bismide (GaAsBi) subcell.
• To demonstrate the integration of high crystalline quality GaAsBi using a compositionally step-graded InGaAs buffer layer.
• To report the performance and identify improvement pathways for this new solar cell architecture.

Main Methods:

• Growth of AlGaAs/GaAs/GaAsBi solar cells via molecular-beam epitaxy.
• Integration of GaAsBi absorber using a step-graded InGaAs buffer layer.
• Characterization of solar cell performance under AM1.5G spectrum.

Main Results:

• Achieved 19.1% power conversion efficiency.
• Recorded an open-circuit voltage of 2.51 V.
• Measured a short-circuit current density of 9.86 mA/cm².
• Identified specific areas for improving the GaAsBi subcell and overall device performance.

Conclusions:

• This study is the first to report multi-junction solar cells incorporating GaAsBi.
• The developed AlGaAs/GaAs/GaAsBi cell demonstrates potential for advanced photovoltaic applications.
• Bismuth-containing III-V alloys show promise for future photonic and solar cell designs.