Expanding the Emission of CsPbBr₃ Nanocrystals in the Blue Region

Abstract

We report blue emission, along with the characteristic green emission, in CsPbBr 3 nanocrystals (NCs) due to the doping of Eu 2+ ions. The doping of Eu 2+ was confirmed using TEM-EDAX, FTIR, and XPS techniques. The undoped CsPbBr 3 NCs show sharp green emission peaking at 515 nm (fwhm ∼24 nm). Whereas Eu 2+ :CsPbBr 3 NCs show two emission peaks at 498 and 442 nm with fwhm ∼20 and ∼13 nm, respectively. A shift in the green emission of doped NCs is because of reduced average particle size from 19 to 7 nm. The additional emission peak at 442 nm is assigned due to the 4f 6 ( 7 F J )5d 1 → 4f 7 transition of Eu 2+ ions. The intensities of blue and green emissions are both significantly influenced by changing the excitation wavelengths. The decay dynamics study suggests an energy transfer from CsPbBr 3 to the Eu 2+ ions. It is also inferred that Eu 2+ doping improves the radiative channels. Further, the CIE coordinate analysis depicts virtuous luminous efficacy of the optical radiation and significant color purity (>85%) of the emission spectra under different excitations. These optical studies show that the Eu 2+ :CsPbBr 3 NCs can be a potential candidate for multicolor LEDs, displays, and anticounterfeiting applications.

Improving the Stability of Lead-Free CsSnBr3 Halide Perovskite by DDAB-Assisted Postpassivation Surface Engineering

“…In recent years, halide perovskites (HPs) have gained enormous research interest because of their appealing optical and electronic properties, such as high absorption coefficient, tunable optical band gap, high photoluminescence quantum yields (PLQY), long carrier lifetime, etc. − Lead-based systems are the most widely explored among the various HPs. − Its ABX 3 perovskite structure consists of monovalent cations, such as methylammonium (MA + ), formamidinium (FA + ), cesium (Cs + ) at the A-site, Pb 2+ at the B-site, and monovalent halides (i.e., Cl ¯ , Br ¯ , or I ¯ ) at the X-site. − Solar cells fabricated using lead-based HPs have achieved a remarkable feat with a reported power conversion efficiency (PCE) of over 25% . Along with that, CsPbBr 3 -based LEDs have been reported with an external quantum efficiency (EQE) of ∼20% and a luminance of 14000 cdm –2 .…”