Permanent bonding process for III-V/Ge multijunction solar cell integration

In this paper, we propose a process to permanently bond multi-junction solar cells (MJSCs) front side to a transparent superstrate using polydimethylsiloxane (PDMS). This process could allow for substrate handling during several fabrication schemes such as thin MJSCs, substrate lift-off /recycling or through cell via contacts (TCVC) solar cells. The developed process is compatible with standard microfabrication processes such as photolithography, etching or metallization. Permanent bonding of III-V/Ge triple junction solar cell on quartz superstrate has been used to handle the solar cell and to demonstrate a 20 µm thick TCVC device. No significant performance loss was observed on I-V characteristics for a bonded triple junction solar cell.