Raman and XPS studies of CIGS/Mo interfaces under various annealing temperatures

• MoSex formation at CIGS/Mo interface at high annealing temperature.
• CIGS/Mo interface, poor in Cu, but rich in Ga and Na.
• CIGS compound splits into binary phases at high temperature.
• Na diffuses deeply into CIGS bulk from interface at high temperature.

In this work, copper indium gallium selenide (CIGS) thin films were prepared by sputtering CIGS quaternary target and subsequent annealing in the 450–550 °C range. For analyses purpose, the films were peeled off from Mo-coated glass and both parts were named as ‘CIGS side’ and ‘Mo side’ respectively. Raman spectroscopy and X-Ray Photoelectron Spectroscopy (XPS) were performed to identify crystalline phases and chemical compositions. On the ‘Mo side’, a MoSex layer was evidenced with increased thickness for higher annealing temperature. On the ‘CIGS side’, XPS highlighted a continuous Ga enrichment and a Cu content decrease with increasing temperature. Na was detected on both Mo and CIGS sides. Its concentration and distribution relied on the temperature. Finally, relationships between interface modifications and annealing temperature were discussed.

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