The layered hybrid double perovskites emerged as excellent semiconductor materials owing to their environment compatibility and stability. However, these materials are weakly luminescent, and their photoluminescence (PL) properties can be modulated via doping. While Mn2+ doping in perovskites is well known, but to the best of our knowledge the doping of Mn2+ in layered double perovskites (LDPs) is yet to be explored. Herein, for the first time, we demonstrate the doping of Mn2+ in hybrid inorganic-organic two-dimensional (2D) LDPs, (BA)4AgBiBr8 (BA = n-butyl amine) via a simple solid-state mechanochemical route. The powder x-ray diffraction pattern, and electron paramagnetic resonance analysis confirm the successful incorporation of Mn2+ ions inside (BA)4AgBiBr8 lattice. The Mn2+ doped 2D LDP shows energy transfer from host excitons to d-electrons of Mn2+ ions, which results in red-shifted broad Mn2+ emission band centered at 625 nm, attributed to the spin-forbidden
4T1 to 6A1 internal transition. This work opens up new possibilities to dope metal ions in 2D LDPs to tune the optical as well as magnetic properties.
The layered hybrid double perovskites (LDPs) possess excellent stability and environmental friendliness, which makes them remarkable semiconducting materials. Contrary to significant advancements, the nonfluorescent nature at ambient temperature and pressure is still a major hurdle in this intriguing family. Here, we demonstrate doping of the transition metal cation Mn 2+ in two-dimensional (2D) (PEA) 4 NaInCl 8 (PEA = phenylethylamine) LDP, by a solution-processed crystallization method. This results in broadband emission at ambient conditions and initial contraction followed by expansion of host lattice on increasing dopant concentration. A higher dopant feed ratio in this wide band gap material leads to the absorption at 2.95 eV due to the 6 A 1 ( 6 S) → 4 A 1 ( 4 G) transitions on Mn 2+ centers. First-principles calculations based on density functional theory (DFT) confirm that Mn 2+ in substitutional sites results in lattice contraction while interstitial site Mn 2+ doping leads to lattice expansion. The potential of Mn 2+ to improve optical and magnetic properties of host lattice and a deeper understanding of distribution of Mn 2+ dopant make these LDPs a promising material for emitters for solid-state lighting and magneto-optical applications.
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.
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