Mn 2+ ions, occupying the substitution position, are preferably incorporated during perovskite nanocrystal formation.

Doping in perovskite nanocrystals adopts different mechanistic approach in comparison to widely established doping in chalcogenide quantum dots. The fast formation of perovskites makes the dopant insertions more competitive and challenging. Introducing alkylamine hydrochloride (RNH Cl) as a promoting reagent, precise controlled doping of Mn in CsPbCl perovskite nanocrystals is reported. Simply, by changing the amount of RNH Cl, the Mn incorporation and subsequent tuning in the excitonic as well as Mn d-d emission intensities are tailored. Investigations suggested that RNH Cl acted as the chlorinating source, controlled the size, and also helps in increasing the number of particles. This provided more opportunity for Mn ions to take part in reaction and occupied the appropriate lattice positions. Carrying out several reactions with varying reaction parameters, the doping conditions are optimized and the role of the promoting reagent for both doped and undoped systems are compared.

Doping Mn2+ in semiconductor nanocrystals is widely known for its long-lifetime Mn d–d orange emission. While this had been extensively studied for chalcogenide nanostructures, recently this was also extended to perovskite nanocrystals. Being that CsPbCl3 has a wide bandgap, the exciton energy transfer was found to be more efficient, but the dopant-induced photoluminescence was also obtained for layered perovskites and quantum-confined CsPbBr3 nanocrystals. In recent years significant advances have been achieved in understanding the physical insights of doping following various approaches and optimizing the conditions for obtaining intense dopant emission. In addition, several new properties associated with these doped nanocrystals were also reported, and by modulating the compositions, the host bandgap and the dopant emission positions were also tuned. Keeping all of these developments in mind, this Perspective focuses on the insights of doping and the photoluminescence properties of Mn2+-doped perovskite nanocrystals. In addition, it also proposes possible future prospects of both synthesis and optical properties of these nanomaterials.

Considering the chemistry of the formation and physics at interfaces, we report on the heterostructure of a promising new energy material, Au–Cu2ZnSnS4 (Au-CZTS), and investigate the impact of coupling on Au on improving both the photostability and the photoresponse behavior. We focus primarily on the fundamental issues involved in bringing together two dissimilar materials having different chemical and physical properties in a single building block where one is a multinary semiconductor nanomaterial and the other is a plasmonic noble metal. The formation of heteroepitaxy at the junction of Au and CZTS was investigated for two different phases of CZTS. Considering epitaxy formation along the {111} planes of Au, it was observed that the wurtzite and tetragonal phases of CZTS exhibit coincident site epitaxy with different periodic intervals. A detailed study of this epitaxy formation with Au in both phases of CZTS has been carried out and reported. Because Au-CZTS is a promising new material, we have further investigated its photocurrent and photoresponse behavior and compared them with the properties and behavior of pure CZTS. We believe that these findings will help the energy-materials community, providing guidelines for investigating new functional materials and their applications.

In nanoscale, with size variation, Au shows different optical behaviors. For the small size clusters (sub-5 nm), it behaves more like semiconductors having sp and d band electronic energy levels splitting and also do not show the characteristic plasmon. However, for larger size particles (>5 nm), it shows the plasmonic absorption. Considering these two structures of Au 0 , we report here their coupling with a low bandgap semiconductor SnS and study the difference in their formation chemistry and materials' properties. Following a common synthetic approach in which a smaller size SnS cube and tetrahedron shapes result in Au cluster decorated Au-SnS heterostructures, larger size SnS cubes form coupled Au-SnS nanostructures. Contrastingly, the nonplasmonic Au 0 cluster-SnS hinders the photocatalytic activity, whereas the plasmonic coupled Au-SnS enhances the catalytic activity toward reduction of organic dye methylene blue. However, both types of heterostructures show enhanced photocurrent as well as photoresponse activities. Details of the chemistry of formation, epitaxy at the junction, and change in the materials' properties are studied and reported here in this article.