Photoluminescence Up-Conversion in CsPbBr₃ Nanocrystals

Abstract

We report the first observation of phonon-assisted photoluminescence up-conversion from CsPbBr3 nanocrystals (NCs) at both the ensemble and single-NC levels. Ensemble up-conversion efficiencies are estimated to be on the order of 75% for a ΔE = 23 meV excitation detuning into the nanocrystal gap.

Rb2CuX3 (X = Cl, Br): 1D All‐Inorganic Copper Halides with Ultrabright Blue Emission and Up‐Conversion Photoluminescence

“…Considering the fact that single crystals of Rb 2 CuCl 3 shows a 100% PLQY, and the maximum ASPL occurs at 395 nm (3.14 eV) under 520 nm (2.385 eV), using the above equation, an optical cooling efficiency of ≈32% is estimated. This value is similar to the highest values recently reported for hybrid perovskite10a,29 and all inorganic metal halides . Further detailed spectroscopic investigations including Raman spectroscopy is in progress to better understand the physical origin of the observed ASPL of Rb 2 CuCl 3 .…”

“…Moreover, for Rb 2 CuCl 3 , our preliminary results indicate a net phonon‐assisted anti‐Stokes photoluminescence (ASPL), and an optical cooling efficiency of ≈32% at room temperature. Note that optical cooling by ASPL (also known as upconversion PL) was previously reported in several rare earth‐based materials, semiconductors such as CdS and more recently in a few hybrid organic–inorganic and all‐inorganic perovskites type materials . This process takes place as a result of a light excitation energy below the bandgap of the material producing a nonequilibrium electron distribution.…”

“…According to the previous studies based on Sheik‐Bahae theory,8,10a,11,28 the optical cooling efficiency can be estimated from the following equation where η C and η PL are the cooling and PL efficiency, respectively, and E em and E ex present the emission and excitation energies. Considering the fact that single crystals of Rb 2 CuCl 3 shows a 100% PLQY, and the maximum ASPL occurs at 395 nm (3.14 eV) under 520 nm (2.385 eV), using the above equation, an optical cooling efficiency of ≈32% is estimated.…”

Progress in laser cooling semiconductor nanocrystals and nanostructures

“…26, we find that CsPbBr 3 and CdSe/CdS NCs possess sizable η ASPL values. Specifically, for CsPbBr 3 NCs, η ASPL = 0.75 (η ASPL = 0.32) for ΔE = 23 (ΔE = 102) meV 103 . For CdSe/CdS core/shell NCs, η ASPL = 0.55 (η ASPL = 0.03) for ΔE = 56.6 (ΔE = 107).…”

“…, CdS 56 , CdSe [58][59][60][61][62]104 , CdTe 59,[63][64][65]105 , PbS 67 , CsPbBr 3 73,103 , and CsPbBrI 2 69,106 . Other nanostructures exhibiting linear I ASPL versus I exc behavior include CdS NBs 47,57,107 , ZnTe nanoribbons 108 , bulk MAPbI 3…”