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The present study reports the preparation and characterization of an orange nanopigment with high solar radiation reflective properties. Complex Cr2O3–3TiO2 nanoparticles were prepared by the pyrolysis of Cr–Ti precursors at high temperature, and the effects of the calcination temperature on the structure of Cr2O3–3TiO2 nanopigment were investigated by thermal analysis, X-ray diffraction, and transmission electron microscopy. The results reveal that the Cr2O–-3TiO2 pigments having rutile structure can be prepared by the calcination of the precursor at above 600 °C. All Cr2O3–3TiO2 pigments are granular in nature and present a homogeneous particle size of around 20 nm. The ultraviolet–visible near infrared (UV–vis-NIR) reflection spectra show that the Cr2O3–3TiO2 nanopigments have a reflection peak at around 600 nm, which reflects the orange color of these pigments. The average reflectance of Cr2O3–3TiO2 in the NIR range is around 53%, respectively, which is much higher than that of the visible light range. The prepared orange Cr2O3–3TiO2 nanopigments have a great potential in applications such as cool materials used for buildings with energy saving performance.

Methylammonium lead triiodide (MAPbI 3 ) perovskite has attracted broad interest for solar cells, light-emitting diodes, and so forth. Experiments have captured that the alternative coexistence of polar and nonpolar domains in MAPbI 3 can be switched by photons and phonons. Therefore, it is urgent to clarify the interplay among the crystal space group, polarity, ferroic properties, and switching mechanisms for MAPbI 3 . Herein, we perform a statistical synthesis on ferroelectric and anti-ferroelectric features for tetragonal MAPbI 3 perovskite. The polar and nonpolar domains are ferroelectric with the I4cm space group and anti-ferroelectric with the I4/mcm space group, respectively.The domain wall (DW) separating nonpolar and polar regions is charged. Combining the effects of the electric properties of ferroic domains and the charged DWs, novel switching mechanisms are proposed in which photons and phonons drive alternations between ferroelectric and anti-ferroelectric domains, which provide a reasonable approach to clarify the ambiguous understanding of ferroic behavior for MAPbI 3 perovskite.

The structural and electronic properties of layered C 3 N compound have been studied using ab initio pseudopotential density-functional method within the local-density approximation. Total energy, lattice constant, band structure, and electron density of state are calculated. Among three possible C 3 N monolayer configurations, the monolayer-I structure with the highest symmetry is the most stable and predicted to be a narrowgap semiconductor with an indirect gap about 0.283 eV.Among four possible C 3 N stacking configurations constructed from hexagonal BN and graphite structures, C 3 N-IV constructed from hexagonal BN is expected to be the most stable structure and has metallic conducting behavior. The structural stability of layered C 3 N has also been checked by the calculations of the formation energies, elastic constants, and phonon frequencies.

Low-leaded perovskite solar cells are operated using inorganic active metal substitution of lesser active organometal halide perovskite.