Efficient Near‐Infrared Luminescence in Lanthanide‐Doped Vacancy‐Ordered Double Perovskite Cs₂ZrCl₆ Phosphors via Te⁴⁺ Sensitization

Abstract

All-inorganic lead-free perovskite-derivative metal halides have shown great promise in optoelectronics, however, it remains challenging to realize efficient near-infrared (NIR) luminescence in these materials. Herein, we report a novel strategy based on Te 4 + /Ln 3 + (Ln = Er, Nd, and Yb) co-doping to achieve efficient NIR luminescence in vacancy-ordered double perovskite Cs 2 ZrCl 6 phosphors, which are excitable by a low-cost near-ultraviolet light-emitting diode (LED) chip. Through sensitization by the spin-orbital allowed 1 S 0 ! 3 P 1 transition of Te 4 + , intense and multi-wavelength NIR luminescence originating from the 4f!4f transitions of Er 3 + , Nd 3 + , and Yb 3 + was acquired, with a quantum yield of 6.1 % for the Er 3 + emission. These findings provide a general approach to achieve efficient NIR emission in lead-free metal halides through ns 2metal and lanthanide ion co-doping, thereby opening up a new avenue for exploring NIR-emitting perovskite derivatives towards versatile applications such as NIR-LEDs and bioimaging.

Emission Mechanism of Self-Trapped Excitons in Sb3+-Doped All-Inorganic Metal-Halide Perovskites

“…19 Doping or alloying an s-electron dopant in bare B-cation sites is one of the most effective strategies for achieving efficient broadband emission. 20,21 Among the diverse s-electron dopants, the Sb 3+ ion has attracted increasing research interest. 22−30 Light emission with high PL quantum yield (PLQY) and color diversity has been achieved in various Sb 3+doped inorganic metal-halide hosts, such as blue-emitting Cs 2 NaInCl 6 :Sb 3 + (PLQY ∼84%), 2 4 green-emitting Cs 2 KInCl 6 :Sb 3+ (PLQY ∼80%), 25 Rb 3 InCl 6 :Sb 3+ (PLQY ∼90%), 26 and Rb 4 CdCl 6 :Sb 3+ (PLQY ∼70%), 27 yellowemitting Cs 2 InCl 5 •H 2 O:Sb 3+ (PLQY ∼96%), 28 and redemitting Cs 2 ZnCl 4 :Sb 3+ (PLQY ∼80%) 29 and Cs 2 SnCl 6 :Sb 3+ (PLQY ∼37%).…”

Doping/Alloying Pathways to Lead‐Free Halide Perovskites with Ultimate Photoluminescence Quantum Yields

“…Isovalent doping of the Cs 2 ZrCl 6 matrix with Te 4+ increases dramatically the absorbance of the host in the near‐UV range and generates yellow STE PL centered at 570–580 nm with a maximal PL QY of ca. 59 % [40] . The Cs 2 ZrCl 6 matrix activated by Te can be further doped with Ln 3+ cations, allowing LnCl 5 octahedra with a single chloride vacancy V Cl (Supporting Information, Figure S3f) to be incorporated.…”

“…The host matrix acts as an antenna for near‐UV light, pumping the Ln 3+ dopants via an energy transfer mechanism resulting in NIR emission with a PL QY reaching ca. 6 % (for Ln=Er) [40] . The Cs 2 ZrCl 6 : Te matrix doped with different lanthanide ions (Er, Nd, Yb) was found to perform as a stable and single‐phase dual‐emission Vis‐NIR phosphor (Supporting Information, Figure S3g) [40] …”

Dotierungs‐/Legierungswege zu bleifreien Halogenid‐Perowskiten mit ultimativen Photolumineszenz‐Quantenausbeuten

“…Die isovalente Dotierung der Cs 2 ZrCl 6 ‐Matrix mit Te 4+ erhöht die Absorption des Wirts im nahen UV‐Bereich dramatisch und erzeugt gelbe STE‐PL mit einem Zentrum bei 570–580 nm und einer maximalen PL‐QA von ca. 59 % [40] . Die durch Te aktivierte Cs 2 ZrCl 6 ‐Matrix kann mit Ln 3+ ‐Kationen weiter dotiert werden, so dass LnCl 5 ‐Oktaeder mit einer einzelnen Chloridvakanz V Cl (Hintergrundinformationen, Abbildung S3f) eingebaut werden können.…”

“…Die Wirtsmatrix wirkt als Antenne für Nah‐UV‐Licht und pumpt die Ln 3+ ‐Dotierstoffe über einen Energieübertragungsmechanismus, der zu NIR‐Emission mit einer PL‐QA von ca. 6 % (für Ln=Er) führt [40] . Die Cs 2 ZrCl 6 : Te‐Matrix, die mit verschiedenen Lanthanoidionen (Er, Nd, Yb) dotiert ist, hat sich als stabiler und einphasiger Vis‐NIR‐Leuchtstoff mit dualer Emission erwiesen (Hintergrundinformationen, Abbildung S3g) [40] …”