Bandgap engineering of lead halide perovskite materials is critical to achieve highly efficient and stable perovskite solar cells and color tunable stable perovskite light-emitting diodes.

Intelligently screening the passivation materials is critical to improving power conversion efficiency (PCE) of the perovskite solar cell (PSC), while it is still lacking. Herein, machine learning is employed to...

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Carbon dots (CDs) are synthesized by the solvothermal method with four kinds of solvents including water, dimethylformamide (DMF), ethanol, and acetic acid (AA). The aqueous solutions of the above CDs emit multiple colors of blue (470 nm), green (500 nm), yellow (539 nm), and orange (595 nm). The structures, sizes, and chemical composition of the CDs are characterized by transmission electron microscopy (TEM), dynamic light scattering (DLS), X-ray diffraction (XRD), Fourier transform infrared (FTIR), and X-ray photoelectron spectroscopy (XPS). The optical properties of multicolored CDs are analyzed by UV−vis absorption and photoluminescence (PL) spectra. It has been revealed that DMF is the key solvent to synthesized CDs for the red shift of fluorescence emission, which could be enhanced by adding an AA solvent. The structures of functional groups such as the contents of graphitic N in carbon cores and oxygencontaining functional groups on the surface of CDs are affected by these four solvents. According to the oxidation and selective reduction of NaBH 4 , the implication for multicolor imaging has been discussed based on the COOH, C−O−C, and CO functional groups.

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A stress‐induced failure study on a high‐temperature air‐stable ceramic composite solar selective absorber (SSA) based on a W–SiO2 system is reported. The as‐prepared SSA exhibits excellent spectral and structural stability after annealing in air at 500 °C for 36 h, proving its thermal stability against air corrosion. However, once the temperature is elevated to 600 °C, optical performance degradation and coating cracking happens. The X‐ray diffraction (XRD) patterns reveal that an O‐induced phase transition process from α‐W to β‐W occurs at the interface between the W IR reflector and W–SiO2 layer during deposition. The phase transition induces immense internal stress, which becomes the incentive of crack generation. Further increasing the annealing temperature, drastic structural changes of oxidized W become the driving force for crack propagation and hole expansion, leading to a failure analogous to a volcanic eruption. To improve the temperature limit of coating, a Ni–SiO2 stress buffer layer is introduced and successfully reduces the internal stress through Ni atom substitution for W atoms. Therefore, the optimized SSA keeps stable at 600 °C and the cracking temperature increases to 650 °C. These results suggest that the W–SiO2‐based SSA is a good candidate for air‐stable high‐temperature solar thermal conversion.