Lead-free halide perovskites have attracted interest in the photovoltaic industry out of concern for the toxic nature of the lead. Antimony-based perovskite, cesium antimony iodide (Cs3Sb2I9), is one such material proposed to substitute the lead-based perovskites, as it has a high absorption coefficient, nearly direct bandgap, and low effective mass. A clear understanding of the stability of this material will bring out its efficient use in photovoltaics. Here we have studied the degradation of both the polymorphs of Cs3Sb2I9 (dimer and layer forms) in water, light, and elevated temperaturethe well-known factors causing degradation in perovskites using X-ray diffraction and thermogravimetric analysis. The layered polymorph is found to be more stable compared to the dimer polymorph. The dimer form completely degrades in ∼49 days and the layer form in ∼88 days, although both polymorphs of Cs3Sb2I9 are relatively more stable than the established organic–inorganic halide perovskites. We found that the diffusion of iodine from the system is the prime reason for the degradation in Cs3Sb2I9. Also, the reactivity of antimony iodide (SbI3) in oxygen adds up to accelerate the degradation process. Light, water, and heat equally cause the degradation of Cs3Sb2I9, and hence, use of this material for application in the ambient atmosphere would need proper encapsulation or necessary measures.

We show that the colloidal growth of SnS nanosheets (NS), a group IV metal chalcogenide (MC), on MoSe2 NS, a transition metal dichalcogenide (TMDC), results in the formation of type-II nanoheterostructures (NHS). The MoSe2/SnS NHS synthesis is accompanied by in situ generation of MoO3–x at the MoSe2 and SnS interface activating the otherwise electrochemically inert basal planes of MoSe2 NS. The MoSe2/SnS NHS exhibit more active sites, and the built-in electric field at the interface enhances the rate of charge transfer. The largely enhanced electrocatalytic activities are attributed to the electronic property manipulation due to the synergistic interactions between MoSe2 NS and SnS NS. This work provides insights into the design of multicomponent low-dimensional 2D/2D (D = dimension) NHS based on TMDC/MC combination with enhanced electrochemical properties, in particular for applications of water splitting.

Anion exchange of CsPbX3 nanocrystals (NCs) is an easy pathway to tune the bandgap over the entire visible region. Even, mixing of pre-synthesized CsPbBr3 and CsPbI3 NCs at room temperature...

Nanoheterostructures (NHSs) based on lead halide perovskites (LHPs) and chalcogenide quantum dots have proved to be promising candidates for photovoltaic device applications. However, understanding the defect chemistry at the interfaces of LHPs and chalcogenides is essential to stabilize them and further tune their optoelectronic properties. Here, we demonstrate a route for designing CsPbBr 3 −PbSe NHSs and other derivatives of LHP-based NHSs using defect-rich MoSe 2 nanosheets (NSs) and study the effect of the size of PbSe NPs on their optical properties. In this synthesis route, PbSe nanoparticles (NPs) are formed at an early stage of the reaction through a unique cation displacement reaction, over which CsPbBr 3 nanocrystals (NCs) are epitaxially grown. Using this methodology, a nearly 3-fold enhancement in photoluminescence (PL) is achieved, whereas other selenium precursors, which form larger PbSe NPs, result in negligible PL enhancement with respect to the pure CsPbBr 3 NCs. Detailed density functional theory (DFT) calculations suggest that the PbSe NPs are responsible for passivating the surface defects that consequently enhance the PL intensity. However, in the case of larger PbSe NPs, the associated valence and conduction bands lie within the band-gap region of CsPbBr 3 , creating a type-I heterostructure between the two materials, thereby affecting the luminescence properties. Strong passivation of surface defects in CsPbBr 3 −PbSe NHSs is also evidenced from low-temperature PL studies. Furthermore, the resulting CsPbBr 3 −PbSe NHSs demonstrate enhanced stability in the presence of water and do not degrade under ambient conditions for several months.