Mechanical reliability of flexible encapsulation of III-V compound thin film solar cells

C Yang and JR Qu and ZY Wu, SOLAR ENERGY, 214, 542-550 (2021).

DOI: 10.1016/j.solener.2020.12.014

Flexible III-V compound thin film solar cells are promising candidates in the applications of Internet of Thing, electronics, civil, automotive and aerospace. In this study, theoretical, numerical and experimental methods are employed to investigate the mechanical reliability of the GaAs thin film solar cells with polymer film encapsulation. Experimental investigation by uniaxial tensile testing has revealed the stress failure of cell can be divided into the two different stages. For lower applied strain (<2.0%), the stress concentration caused the local plasticity of encapsulation material along the polymer-semiconductor interface (e.g. EVA-GaAs). For larger applied strain (>2.0%), semiconductor materials (e.g. junction and window) have shown brittle cracking failures. The observed brittle and ductile failures of the sublayer can be well-explained by analytical model based on theory of solid and fracture mechanics. It is also found that the interface stiffness mismatch plays an important role of encapsulation failure at lower strain level. The degree of the stiffness mismatch can be characterised by the proposed strain intensity factor. To overcome the mechanical failure, new encapsulation material such as ultra-thin glass can be promising in the future application.

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