Photoinduced degradation of thermally stable Cs2AgBiBr6 double perovskites by micro-Raman studies

Abstract

The thermal stability of lead-free double perovskite Cs₂AgBiBr₆ for stable optoelectronic and photovoltaic devices is essential. There are contradicting reports, with some claiming stability from 300 to 400 °C based on X-ray diffraction and thermogravimetry studies and others up to 250 °C from Raman studies for Cs₂AgBiBr₆. We perform thermogravimetry analysis and temperature-dependent Raman studies with different laser intensities and show that Cs₂AgBiBr₆ is thermally stable up to ∼410 °C. A low power (3.68 mW) laser excitation source does not induce any structural changes at all temperatures. On the contrary, higher power laser light (7.15 mW) decomposes Cs₂AgBiBr₆ to Cs₃Bi₂Br₉ at temperatures beyond 180 °C. Meticulous thermogravimetry, Raman, and X-ray diffraction studies confirm that Cs₂AgBiBr₆ is structurally stable up to 410 °C, whereas its stability decreases under light exposure beyond a certain critical intensity. This study brings out the importance of light and thermal stability of Cs₂AgBiBr₆, which is crucial for designing various optoelectronic devices.