Optical Properties of (Zn, Mn) and (Cd, Mn) Chalcogenide Mixed Crystals and Superlattices

Mn2+-Doped Metal Halide Perovskites: Structure, Photoluminescence, and Application

Biomedical imaging and labeling through luminescence microscopy requires materials that are active in the near-infrared spectral range, i.e., within the transparency window of biological tissue. For this purpose, tailoring of Mn2+-Mn2+ activator aggregation is demonstrated within the ABF3 fluoride perovskites. Such tailoring promotes distinct near-infrared photoluminescence through antiferromagnetic super-exchange across effective dimers. The crossover dopant concentrations for the occurrence of Mn2+ interaction within the first and second coordination shells comply well with experimental observations of concentration quenching of photoluminescence from isolated Mn2+ and from Mn2+-Mn2+ effective dimers, respectively. Tailoring of this procedure is achieved via adjusting the Mn-F-Mn angle and the Mn-F distance through substitution of the A+ and/or the B2+ species in the ABF3 compound. Computational simulation and X-ray absorption spectroscopy are employed to confirm this. The principle is applied to produce pure anti-Stokes near-infrared emission within the spectral range of ≈760-830 nm from codoped ABF3:Yb3+,Mn2+ upon excitation with a 976 nm laser diode, challenging the classical viewpoint where Mn2+ is used only for visible photoluminescence: in the present case, intense and tunable near-infrared emission is generated. This approach is highly promising for future applications in biomedical imaging and labeling.

Tailored Near-Infrared Photoemission in Fluoride Perovskites through Activator Aggregation and Super-Exchange between Divalent Manganese Ions.

Tunable optical emission properties from ferromagnetic semiconductors have not been well identified yet. In this work, high-quality Mn(II)-doped CdS nanowires and micrometer belts were prepared using a controlled chemical vapor deposition technique. The Mn doping could be controlled with time, precursor concentration and temperature. These wires or belts can produce both tunable redshifted emissions and ferromagnetic responses simultaneously upon doping. The strong emission bands at 572, 651, 693, 712, 745, 768, 787 and 803 nm, due to the Mn(II) (4)T1((4)G)  → (6)A1((6)s) d-d transition, can be detected and accounted for by the aggregation of Mn ions at Cd sites in the CdS lattice at high temperature. These aggregates with ferromagnetism and shifted luminescence are related to the excitonic magnetic polaron (EMP) and localized EMP formations; this is verified by ab initio calculations. The correlation between aggregation-dependent optical emissions and ferromagnetic responses not only presents a new size effect for diluted magnetic semiconductors (DMSs), but also supplies a possible way to study or modulate the ferromagnetic properties of a DMS and to fabricate spin-related photonic devices in the future.

http://iopscience.iop.org/article/10.1088/0957-4484/25/38/385201/pdf

Tunable emission properties by ferromagnetic coupling Mn(II) aggregates in Mn-doped CdS microbelts/nanowires.

The magnetic coupling interaction of Mn2+-Mn2+ in Mn2+-included phosphors could induce a shorter emission decay time, compared with that of isolated Mn2+, which could overcome the photoluminescence (PL) saturation when stimulated by a high photon flux due to the long lifetime of the Mn2+ excited state. However, few studies have directly proved the Mn2+-Mn2+ coupling effect on the PL decay. In this paper, the effect on PL of CsMnCl3 (CMC) and its hydrates is revealed by photomagnetism results, excluding the interference effects of site symmetry and phonon energy. The antiferromagnetic interaction of the CMC is larger when Mn2+ at a photoexcited state than at a dark state, which is contrary to the hydrates with weak Mn2+-Mn2+ interaction. This research not only helps researchers to understand the fundamental optical process but also is instructive for designing high performance Mn2+-doped phosphors in the field of displays and lighting.

Mn2+-Mn2+ Magnetic Coupling Effect on Photoluminescence Revealed by Photomagnetism in CsMnCl3.

On the Mn-Mn Interaction and the Structure of Optical Spectra of ZnS(Mn

The infrared luminescence of ZnS(Cu) due to internal transitions within the 3d9 configuration of Cu2+ ions excited by radiation may be modulated by electric ac fields (field modulation). The experimental data lead to the conclusion that the modulation of the emission is caused by field-induced density oscillations of free electrons within the ZnS lattice. The infrared Cu2+ emission may also be obtained without exciting radiation by the action of the electric ac field (electroluminescence). The infrared electroluminescence may be stimulated or quenched by additional irradiation.



Die durch Strahlung angeregte infrarote Cu-Lumineszenz in ZnS, die von inneren Ubergangen der 3d9-Konfiguration herruhrt, last sich durch elektrische Wechselfelder modulieren (Feldmodulation). Die experimentellen Ergebnisse fuhren zu dem Schlus, das die Modulation der Emission durch Oszillationen der Dichte freier Elektronen im elektrischen Feld verursacht wird. Die infrarote Cu2+-Emission kann ohne Strahlung durch die alleinige Wirkung eines elektrischen Wechselfeldes angeregt werden (Elektrolumineszenz). Die infrarote Elektrolumineszenz last sich durch zusatzliche Bestrahlung verstarken oder abschwachen.

Modulation and Excitation of the Infrared Luminescence of ZnS(Cu) by Electric AC Fields

Elektrolumineszenz bei der Temperatur des flüssigen Heliums und Nachweis von Haftstellen sehr geringer energetischer Tiefe

Die Elemente Fe, Co und Ni der Eisengruppe wirken im allgemeinen als “Killer” fur die sichtbare Lumineszenz, wohingegen ihr Einflus auf die Aufbauperiode der Elektrolumineszenz von ZnS(Cu) von der Wahrscheinlichkeit des Ladungsuberganges zwischen den Lumineszenzzentren und diesen Elementen abhangt. Die modulierte Elektrolumineszenz eines mit Kobalt dotierten Phosphors steigt zunachst bis zu einem Maximum an und fallt dann wieder ab, bis der niedrigere stationare Wert erreicht ist. Dieses Maximum ist eine Funktion der Temperatur, der Kobaltkonzentration und der Grose und Frequenz des elektrischen Feldes. Die Temperatur- und Frequenzabhangigkeit des absoluten Maximums wahrend der Aufbauperiode ist dem Temperatur- und Frequenzverhalten der Killerwirkung des Kobalts auf die Lumineszenz sehr ahnlich. Die Elektrolumineszenz von ZnS(Cu), das mit Fe oder Ni dotiert ist, steigt jedoch monoton nach dem Beginn der Anregung durch das elektrische Feld an, wobei kein Maximum erreicht wird, wahrend die Lumineszenz wie beim Co getilgt wird. Diese Ergebnisse werden durch verschiedene Ladungsanderungsmechanismen erklart. Fur Co mus der Ladungsaustausch mit Elektroneneinfang, Co++ Co+, eher stattfinden, als die Killerwirkung der Lumineszenz wirksam wird. Dagegen erscheint die volle Killerwirkung von Fe und Ni unmittelbar nach Einsetzen der Anregung, weil die Ladungsanderung Ni++ Ni+++ und Fe++ Fe+++ in ZnS sehr schnell verlauft.



The iron group elements Fe, Co, and Ni generally destroy visible luminescence whereas their influence on the built-up-period of electroluminescence of ZnS(Cu) depends on the probability of charge transfer between the luminescence centres and these elements. The modulated electroluminescence of cobalt doped phosphors increases at first to a maximum and then decreases until the lower steady-state value is reached. This maximum is a function of temperature, cobalt concentration, and the magnitude and frequency of the electric field. The temperature and frequency dependence of the absolute maximum within the built-up-period is very similar to the temperature and frequency dependence of the luminescence killing action of cobalt. The electroluminescence of ZnS(Cu) doped with Fe or Ni, however, increases monotonically after the beginning of the excitation by an electric field without reaching a maximum, whereas the luminescence is quenched, as in the case of Co. These results are explained by different charge-transfer mechanisms. For Co, the chargetransfer Co++ Co+, involving electron capture, has to take place before the luminescence killing action becomes efficient. However the full killing action of Fe and Ni occurs immediately after the beginning of the excitation because the charge-transfer Ni++ Ni+++ and Fe++ Fe+++ is very rapid in ZnS.

E. Neumann

Papers

On the Mn-Mn Interaction and the Structure of Optical Spectra of ZnS(Mn

Modulation and Excitation of the Infrared Luminescence of ZnS(Cu) by Electric AC Fields

Elektrolumineszenz bei der Temperatur des flüssigen Heliums und Nachweis von Haftstellen sehr geringer energetischer Tiefe

Die Rekombinationsverteilung in der instationären Phase der Elektrolumineszenz von ZnS‐Phosphoren mit Eisengruppenelementen