Achieving Large‐Area, Crack‐Free Epitaxial Lift‐Off of Inverted Metamorphic Multijunction Solar Cells by Ag Electrode Extension and the Counterintuitive Use of Temporary Rigid Carrier

Abstract

The material choices for highly efficient multijunction solar cells (MJSCs) can be expanded by stacking lattice‐mismatched III–V materials grown by the inverted metamorphic approach. However, III–V materials are expensive, necessitating low‐cost strategies such as substrate reuse by epitaxial lift‐off (ELO) to improve their technology readiness. Inverted metamorphic MJSCs (IMM‐MJSCs) are inherently fragile due to the interfacial stresses introduced by graded buffer layers between mismatched materials. While numerous studies have reported successful fabrication of crack‐free IMM‐MJSCs, comprehensive procedural details and critical considerations are often left undisclosed. Herein, a systematic method is presented for achieving large‐area, crack‐free thin‐film IMM‐MJSCs. Specifically, the efficacy of the ELO bath method combined with Ag back electrode extension and the innovative application of rigid, acid‐ and polar solvent‐resistant plastics as temporary carriers during the process is demonstrated. By addressing the challenges of mechanical fragility and developing robust ELO techniques, this work aims to enable the practical implementation of high‐efficiency IMM‐MJSCs for space and terrestrial applications.