Manganese‐Doping‐Induced Quantum Confinement within Host Perovskite Nanocrystals through Ruddlesden–Popper Defects

Abstract

The concept of doping Mn2+ ions into II–VI semiconductor nanocrystals (NCs) was recently extended to perovskite NCs. To date, most studies on Mn2+ doped NCs focus on enhancing the emission related to the Mn2+ dopant via an energy transfer mechanism. Herein, we found that the doping of Mn2+ ions into CsPbCl3 NCs not only results in a Mn2+‐related orange emission, but also strongly influences the excitonic properties of the host NCs. We observe for the first time that Mn2+ doping leads to the formation of Ruddlesden–Popper (R.P.) defects and thus induces quantum confinement within the host NCs. We find that a slight doping with Mn2+ ions improves the size distribution of the NCs, which results in a prominent excitonic peak. However, with increasing the Mn2+ concentration, the number of R.P. planes increases leading to smaller single‐crystal domains. The thus enhanced confinement and crystal inhomogeneity cause a gradual blue shift and broadening of the excitonic transition, respectively.

Switching on Near-Infrared Light in Lanthanide-doped CsPbCl3 Perovskite Nanocrystals.pdf

“…The PL results reveal that the CsPbCl3 NCs doped with 1.41% Mn 2+ doping concentration (relative to Pb 2+ , see Table S1), as determined from X-ray fluorescence (XRF) measurements show the highest PLQY of about 28% for Mn 2+ emission ( Figure S2), in agreement with previous reports. [11,[33][34][35] Three NIR-emitting Ln 3+ ions (Er 3+ , Ho 3+ and Nd 3+ ) have been codoped with Mn 2+ (denoted as Mn-Er, Mn-Ho and Mn-Nd) into CsPbCl3 NCs while keeping the nominal Mn 2+ content fixed. The actual concentrations in Mn 2+ -Er 3+ , Mn 2+ -Ho 3+ and Mn 2+ -Nd 3+ codoped NCs were measured to be 1.03%/0.24%, 0.86%/0.17% and 1.19%/4.93% by XRF analysis (Table S1), respectively.…”

“…Among the various optically active metal cation dopants so far explored in the CsPbCl3 matrix, Mn 2+ is the most investigated one, exhibiting intense broad band emission at ~600 nm originating from the 4 T1 → 6 A1 d-d transition with a full width at half-maximum (FWHM) of ~90 nm. [11,[32][33][34][35][36][37][38][39] Notably, the Mn 2+ emission overlaps strongly with the absorption lines of most NIR-emitting Ln 3+ such as Er 3+ , Ho 3+ and Nd 3+ ( Figure S1). Very recently, Chen and coworkers combined the two most popular luminescent metal ion dopants, Mn 2+ and Yb 3+ , in CsPbCl3 NCs to obtain multiple emissions in LHP NCs and suggested the possible occurrence of an active energy-transfer pathway from Mn 2+ to Yb 3+ .…”

Halide Perovskite Nanocrystal Emitters

“…At high dopant (e.g., Mn) concentrations, there is a potential to observe strong Mn 2+ –Mn 2+ interactions, resulting in a sharp reduction of the Mn 2+ ‐related PLQY due to the formation of the defects in the mid bandgap of the host PNCs induced by the excess of Mn doping. [ 89 ] These formed small Mn 2+ clusters can increase the number of electron traps leading to an energy loss in the form of nonradiative recombination. Therefore, it is undoubtedly urgent to thoroughly investigate the doping‐induced lattice rearrangement and the resultant effect on the PL (excitonic) properties with more research efforts.…”

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

“…Thus, several kinds of metal ions including Cu 2+ , Ni 2+ , Mn 2+ and trivalent rare earth elements have been introduced into halide perovskites for obtaining ideal photophysical properties. [ 76–87 ] Among them, transition metal Mn 2+ ion is widely studied, because the presence of Mn 2+ ions will generate new optical features, moreover, it will produce new chemical and physical properties, including passivated grain boundaries or decreased defect state density, enhanced PLQY, and improved stabilities, which is important for the technological applications.…”