(211h) Thermal Reliability and Degradation of CsPbBr3 Nanocrystals and Their Impact on Optical Properties and Structural Integrity in Optoelectronic Applications

The rapid advancement in nanotechnology has brought cesium lead bromide (CsPbBr3) nanocrystals (CPB NCs) to the forefront of materials for optoelectronic applications. As a part of the all-inorganic perovskite family, CPB NCs have attracted significant attention due to their remarkable optical properties, such as a direct bandgap and high photoluminescence quantum yield, making them highly desirable for use in light-emitting diodes (LEDs), solar cells, and photodetectors. The thermal reliability of CsPbBr3-based devices is a crucial factor for their performance and stability, as it affects their ability to withstand thermal stress during operation or fabrication, impacting both their optical properties and structural integrity. However, like other perovskite materials, CPB NCs are susceptible to thermal degradation, which can manifest as phase transitions, changes in crystal structure, and alterations in optical properties. In this paper, we discuss the thermal reliability of CPB NCs regarding their changes in optical properties and thermal degradation regarding at various temperatures. CPB NCs synthesized by hot injection method dispersed in n-heptane as colloidal were stored at -20°C, 25°C and 70°C while TEM images, Photoluminescence (PL) intensity, UV-vis absorbance and X-ray diffraction were conducted to observe thermal stability of CPB NCs. The particle size of CPB NCs stored at 70°C increased by 46.8 % over 30 days, but the size of CPB NCs stored at -20°C and 25°C increased by only 7.83 % and 13.4 % respectively. PL intensity peak for CPB NCs stored at 70 °C showed red-shift of 5nm over 30 days, while CPB NCs stored at - 20°C and 25°C showed no shift. XRD patterns showed peaks corresponding to the (100), (110), and (200) planes of CPB NCs. At -20°C and 25°C, the intensity ratio of the (100) to (110) peaks remained relatively unchanged over 30 days, while the intensity of the (110) peak increased relative to the (100) at 70 °C after 10 days. Additionally, storage at 70°C led to shifts in the (200) XRD peak, indicating crystal structure distortion by analyzing FFT of TEM images. The structures of CPB NCs stored at 25 °C remained unaffected under TEM beam exposure, while CPB NCs stored at 70 °C led to crystal degradation under TEM beam with a dose rate of 5780 e/Ųs for 300 seconds.