Organic/inorganic hybrid perovskite materials, such as CH₃NH₃PbX₃ (X = I, Br), have attracted the attention of the scientific community due to their excellent properties such as a widely tunable bandgap, high optical absorption coefficient, excellent power conversion efficiency, etc. The exposure of perovskite solar cells and photovoltaic devices to heat can significantly degrade their performance. Therefore, elucidating their temperature-dependent optical properties is essential for performance optimization of perovskite solar cells. We synthesized CH₃NH₃PbBr₃ (MAPbBr₃) single crystals through the polymer-controlled nucleation route and investigated the optical properties and molecular structure evolution of them with temperature. Through temperature evolution photoluminescence (PL) spectroscopy, we found that the fluorescence intensity was greatly affected by increasing the temperature, with an asymmetric PL profile suggesting that more captured excitons undergo radiative complexation. The optical photographs showed that the color of MAPbBr₃ single crystals faded. Raman spectroscopy revealed that during the heating process, the structure of MAPbBr₃ was still preserved at 90 °C since all of the Raman bands were very clear. When the temperature increased to 120 °C, the Raman bands of the internal modes became very weak. On further heating, the inorganic framework on sample’s surface started to disintegrate above 210 °C. During the heating process, the PL spectra exhibited significant changes in spectral intensity, peak position and Full Width Half Maximum (FWHM). The PL spectral intensity decreased abruptly with increasing temperature. The peak position was blue shifted with increasing temperature, and the peak shape showed an obvious asymmetry. The FMWH of the PL spectra was gradually broadened with the increase in the temperature, and there was a sharp increase from 270 °C to 300 °C. These variations in the PL spectra with temperature indicate that the optical properties of MAPbBr₃ are greatly affected by temperature, which in turn affects the application of MAPbBr₃ in fields such as optical devices. These results may be instructive for the application of MAPbBr₃.

Calibration is one of the most important factors affecting the measurement accuracy of X-ray energy/wavelength-dispersive spectrometers (EDS/WDSs). In this work, three Cu content reference materials used in AlCu films for X-ray EDS/WDS calibration are prepared using magnetron sputtering deposition. The Cu content standard values of the three reference materials are determined using an inductively coupled plasma optical emission spectrometer (ICP-OES) and the uncertainties of the reference materials are evaluated. The results show that the homogeneity and stability of the three Cu content reference materials used in AlCu films meet the requirements. The Cu content standard values of the three reference materials are 2.56%, 14.64%, and 49.46% (mass fraction), respectively. Their extended uncertainties are 0.14%, 0.42%, and 0.98% (k = 2), respectively. Using quantitative analysis, it was determined that the three developed reference materials meet the calibration requirements of X-ray EDS/WDS, thus guaranteeing the accuracy and consistency of the measurement results.