Cu⁺ → Mn²⁺ Energy Transfer in Cu, Mn Coalloyed Cs₃ZnCl₅ Colloidal Nanocrystals

Abstract

In this work, we report the hot-injection synthesis of Cs3ZnCl5 colloidal nanocrystals (NCs) with tunable amounts of Cu+ and Mn2+ substituent cations. All the samples had a rodlike morphology, with a diameter of ∼14 nm and a length of ∼30–100 nm. Alloying did not alter the crystal structure of the host Cs3ZnCl5 NCs, and Cu ions were mainly introduced in the oxidation state +1 according to X-ray photoelectron and electron paramagnetic resonance spectroscopies. The spectroscopic analysis of unalloyed, Cu-alloyed, Mn-alloyed, and Cu, Mn coalloyed NCs indicated that (i) the Cs3ZnCl5 NCs have a large band gap of ∼5.35 eV; (ii) Cu­(I) aliovalent alloying leads to an absorption shoulder/peak at ∼4.8 eV and cyan photoluminescence (PL) peaked at 2.50 eV; (iii) Mn­(II) isovalent alloying leads to weak Mn PL, which intensifies remarkably in the coalloyed samples, prompted by an energy transfer (ET) process between the Cu and Mn centers, favored by the overlap between the lowest (6A1 → 4T1) transition for tetrahedrally coordinated Mn2+ and the PL profile from Cu­(I) species in the Cs3ZnCl5 NCs. The efficiency of this ET process reaches a value of 61% for the sample with the highest extent of Mn alloying. The PL quantum yield (QY) values in these Cu, Mn coalloyed NCs are lower at higher Mn contents. The analysis of the Mn PL dynamics in these samples indicates that this PL drop stems from inter-Mn exciton migration, which increases the likelihood of trapping in defect sites, in agreement with previous studies.

Light Emission from Low‐Dimensional Pb‐Free Perovskite‐Related Metal Halide Nanocrystals

“…[ 65 ] Liu et al. [ 66 ] reported Cu, Mn coalloyed 0D Cs 3 ZnCl 5 NCs, in which the Mn 2+ emission at 2.37 eV was activated upon the excitation of the Cu + states, indicating an effective energy transfer between the Cu and Mn centers. Nevertheless, the PLQY of this coalloyed system was only around 3%.…”

“…Indeed Sb-doped Cs 2 Zn(Cl/Br) 4 bulk single crystals have been reported to feature a STE emission at 745-823 nm with a PLQY of almost 70%, making them potential light sources for night vision. [65] Liu et al [66] reported Cu, Mn coalloyed 0D Cs 3 ZnCl 5 NCs, in which the Mn 2+ emission at 2.37 eV was activated upon the excitation of the Cu + states, indicating an effective energy transfer between the Cu and Mn centers. Nevertheless, the PLQY of this coalloyed system was only around 3%.…”

Bandgap narrowing and piezochromism of doped two-dimensional hybrid perovskite nanocrystals under pressure

“…Through energy transfer between two different excited states, dual emission exhibits visually distinguishable luminescence that enriches the optical properties of the perovskites. 8,9 The doping of 2D perovskites can further improve their photoluminescence quantum yield (PLQY) values, and achieve a wide color gamut display. [10][11][12][13][14] As a typical example, Mn 2+ doping in 2D perovskites has been achieved using a simple direct synthesis method, leading to perovskites with the characteristic Mn 2+ dual-emission.…”

Ultrathin Light-Emitting Diodes with External Efficiency over 26% Based on Resurfaced Perovskite Nanocrystals

“…In the past few years, prized for their advantageous optical properties and affordable solution processability, lead halide perovskite nanocrystals (PNCs) have emerged as promising active materials in a wide range of photonic and optoelectronic technologies, spanning from photovoltaic cells, − lasers, , data communication, and radiation detectors − to luminescent solar concentrators , and artificial light sources. − Light-emitting diodes based on PNCs (PNC-LEDs) − have experienced a particularly steep growth, , owing to the efficient, spectrally tunable, narrow luminescence of PNCs and their defect-tolerant electronic structure. ,− Building upon these unique qualities of PNCs, extensive research in material design, morphology/interfacial control, surface chemistry, ,,,,− ,− and energy level engineering (via doping or alloying) ,, has been dedicated to understanding and suppressing detrimental surface defectsacting both as traps for electrically injected carriers and as nonradiative quenching centers for the resulting excitonic luminescenceand to devise suitable molecular ligands and solution-based protocols for fabricating high-quality, low-resistance PNC active layers. ,,,,,− These efforts have enabled researchers to incorporate PNCs with ∼100% photoluminescence (PL) quantum yield (Φ PL ) in devices featuring near-unity carrier mobility ratio (γ),…”