Double Perovskite Nanocrystals Research Articles

Bi3+/Sb3+-doped Cs2Na (Yb/Er) Cl6 double perovskite nanocrystals: Fabrication, optical properties and temperature sensing

Rare-earth-based double perovskites exhibit excellent thermal, water, and oxygen stability, making them promising environmentally friendly materials for various applications such as anti-counterfeiting, LED technology, infrared imaging, and photodetectors. In this study, we utilized the hot injection method to prepare Cs2NaYbCl6:Er3+/Bi3+/Sb3+ double perovskite nanocrystals, realizing upconversion visible and downshifting NIR emission under 980 nm and 1550 nm excitation, and their luminescence and dynamics as a function of temperature were further investigated. The luminescence intensity of Er3+ in Cs2NaYb0.85Er0.15Cl6 can be improved by Sb3+ or Bi3+ doping, and they exhibited the temperature dependent visible and NIR emission with an optimum temperature around 100–130 K. Furthermore, the intensity ratios of RH/S and Rr/g increase consistently with temperature in the range of 80–310 K. The temperature sensing sensitivity of Cs2NaYb0.845Er0.15Sb0.005Cl6 at 310 K increases from 2.39 % K−1 to the relative sensitivity (SR) of 2.90 % K−1 for Cs2NaYb0.85Er0.15Cl6. Our work providing a detailed understanding on the luminescent performance of perovskites through transition metal doping, expanding their temperature sensing application.

Lead-free double perovskite Cs2NaInCl6 nanocrystals doped with Sb3+ and Tb3+ for copper ions detection in lubricating oil

Detecting heavy metal copper ions in lubricating oil holds immense significance for assessing mechanical wear and predicting mechanical failure. While perovskite nanocrystals offer high sensitivity in detecting copper ions, traditional lead halide perovskites suffer from lead toxicity defects. Lead-free perovskites, like Cs2NaInCl6, avoid the issue of lead toxicity but display lower luminescence intensity due to the presence of forbidden optical transitions. To address these issues, this study synthesized Cs2NaInCl6 nanocrystals (NCs) co-doped with Sb3+ and Tb3+ ions for copper ions detection in lubricating oil. The introduction of Sb3+ effectively reduced the band gap of the Cs2NaInCl6 host, creating an energy transfer pathway for Tb3+ emission via self-trapped excitations (STEs). Moreover, the doping of Tb3+ ions resulted in the suppression of STEs emission due to electron transfer from STEs to Tb3+. The emission of Tb3+ increased initially and then decreased with the increasing Tb3+ concentration, peaking at 40 %. Finally, Cs2NaInCl6: 2.5 %Sb3+, 40 %Tb3+ NCs were employed as probes for copper ions detection, exhibiting superior sensitivity and selectivity compared to similar probes. The presence of copper ions introduced competition between copper and Tb3+ for electrons from STEs, consequently leading to the quenching of multiple emission intensities associated with STEs and Tb3+. This method shows promising potential in predicting mechanical failure.

Controlled Synthesis of Lead-Free Double Perovskite Colloidal Nanocrystals for Nonvolatile Resistive Memory Devices.

Although lead-free double perovskites such as Cs2AgBiBr6 have been widely explored, they still remain a daunting challenge for the controlled synthesis of lead-free double perovskite nanocrystals with highly tunable morphology and band structure. Here, we report the controlled synthesis of lead-free double perovskite colloidal nanocrystals including Cs2AgBiBr6 and Cs2AgInxBi1-xBr6 via a facile wet-chemical synthesis method for the fabrication of high-performance nonvolatile resistive memory devices. Cs2AgBiBr6 colloidal nanocrystals with well-defined cuboidal, hexagonal, and triangular morphologies are synthesized through a facile wet-chemical approach by tuning the reaction temperature from 150 to 190 °C. Further incorporating indium into Cs2AgBiBr6 to synthesize alloyed Cs2AgInxBi1-xBr6 nanocrystals not only can induce the indirect-to-direct bandgap transition with enhanced photoluminescence but also can improve its structural stability. After optimizing the active layers and device structure, the fabricated Ag/polymethylene acrylate@Cs2AgIn0.25Bi0.75Br6/ITO resistive memory device exhibits a low power consumption (the operating voltage is ∼0.17 V), excellent cycling stability (>10 000 cycles), and good synaptic property. Our study would enable the facile wet-chemical synthesis of lead-free double perovskite colloidal nanocrystals in a highly controllable manner for the development of high-performance resistive memory devices.

How Does Local Strain Affect Stokes Shifts in Halide Double Perovskite Nanocrystals?

Lead-free perovskite nanocrystals are of interest due to their nontoxicity and potential application in the display industry. However, engineering their optical properties is nontrivial and demands an understanding of emission from both self-trapped and free excitons. Here, we focus on tuning silver-based double perovskite nanocrystals' optical properties via two iso-valent dopants, Bi and Sb. The photoluminescence quantum yield of the intrinsic Cs2Ag1-yNayInCl6 perovskite increased dramatically upon doping. However, the two dopants affect the optical properties very differently. We hypothesize that the differences arise from their differences in electronic level contributions and ionic sizes. This hypothesis is validated through absorption and temperature dependence photoluminescence measurements, namely, by employing the Huang-Rhys factor, which indicates the coupling of the exciton to the lattice environment. The larger ionic size of Bi also plays a role in inducing significant microstraining verified via synchrotron measurements. These differences make Bi more sensitive to doping concentration over antimony which displays brighter emission (QY ∼40%). Such understanding is important for engineering optical properties in double perovskites, especially in light of recent achievements in boosting the photoluminescence quantum yield.

Ultrawide UV to NIR Emission in Double Perovskite Nanocrystals via the Self-Trapping State Engineering Strategy

Ultrawide UV to NIR Emission in Double Perovskite Nanocrystals via the Self-Trapping State Engineering Strategy

Bright Green-Emitting All-Inorganic Terbium Halide Double Perovskite Nanocrystals for Low-Dose X-ray Imaging.

Inorganic halide double perovskite (DP) nanocrystals (NCs) have attracted great attention because of their nontoxicity, mild reaction conditions, good stability, and excellent optical and optoelectronic properties. Herein, we prepare the inorganic terbium halide DP Cs2BTbCl6 (B = Na or Ag) NCs with bright green photoluminescence (PL) emission. The Na-Tb-based DP NCs exhibit better PL properties compared with the Ag-Tb-based DP NCs, which is due to Cs2NaTbCl6 NCs having a more localized charge carrier distribution on the [TbCl6]3- octahedron. The incorporation of Sb3+ dopant in Cs2NaTbCl6 NCs can construct a more efficient energy transfer process, resulting in a doubling of PL efficiency. Furthermore, Cs2NaTbCl6: Sb3+ NCs possess excellent X-ray scintillating performance with a low-dose detection limit of 140 nGyair/s, which is nearly 5 times more sensitive than the undoped NCs. The optimized NCs show great application prospects in X-ray imaging. This work helps deepen the understanding of the luminescence mechanism, excited state dynamics, and scintillation property in Tb-based DP NCs.

Compositionally engineered vacancy-ordered double-perovskite nanocrystals for photovoltaic application

Lead-free double perovskites, in particular tin-based perovskites, have emerged to be a promising photo-absorber in solar cells for attaining protruding efficiency and stability. However, the tin-based double perovskite nanocrystals are yet to be investigated in photovoltaics. There are several advantages of nano-crystals over their bulk counterpart, including tunable band gap, higher fluorescence, and higher carrier lifetime, to name a few. In this work, we synthesized vacancy-ordered Cs2SnI6 nanocrystals (NC) and explored their potential in solar cell applications as a photo-absorber for the first time. Due to the 4+ oxidation state of Sn, this perovskite has a high stability against oxidation and hydrolysis during manufacturing and device operation. We also incorporated alkali-metal ion Rb+ in the Cs2SnI6 NCs for a possible enhancement of efficiency and stability in photovoltaic cells. Better carrier extraction was found through this incorporation as the optical band gap of the NCs is narrowed down to 1.39 eV. The Density Functional Theory (DFT) study revealed the change in the electronic band gap and density of states (DOS) of the NCs upon Rb-doping. The photovoltaic device fabricated with the FTO/TiO2/(Cs1−xRbx)2SnI6 NC/CuI/Au architecture has achieved a maximum efficiency of 0.71% with an inspiring short-circuit current (Jsc) of ∼5 mA/cm2. The champion cell has also shown remarkable stability after ∼40 days in an ambient atmosphere. This work, therefore, provides new insights into the alkali-metal ion regulated lead-free fully inorganic perovskite NCs for stable photovoltaic application.

Sb3+ and Sm3+ co-doped lead-free Cs2NaInCl6 double perovskite nanocrystals for single-component cold white emitter

Metal halide perovskites exhibit promising prospect in light-emitting diodes, solar cells, photodetectors and bioimaging. However, the workhorse of metal halide perovskites relies on toxicity lead element, which severely damages human body and environment. Among lead-free perovskites, Cs2NaInCl6 double perovskite is one of the most promising candidates because of its great stability and easy synthesis, but suffers inadequate optical performance. Here, we doped Sb3+ and Sm3+ into Cs2NaInCl6 nanocrystals by a hot injection method. Cs2NaInCl6:Sb3+ exhibits blue emission at 447 nm. Cs2NaInCl6:Sm3+,Sb3+ nanocrystals simultaneously generate the blue emission of Sb3+ and the multiple emissions of Sm3+ at 565, 602, 650 and 710 nm. With the increase of Sm3+ feed ratio, the emission color of Cs2NaInCl6:Sm3+,Sb3+ gradually moves to cold white region at (0.27, 0.28) in CIE chromaticity diagram and correlated color temperature of 11840 K. This work shows the potential application of Cs2NaInCl6:Sm3+,Sb3+ nanocrystals as a single-component cold white emitter.

Enhanced optical properties of lead-free double perovskite Cs2AgBiBr6 nanocrystals by doping of Na ions

Lead free double perovskite nanocrystals is an ideal alternate considering its nontoxic and stable property comparing with their counterpart lead halide perovskite NCs. A simple solution synthesis strategy was used to prepare lead-free double perovskite Cs2AgBiBr6 nanocrystals (NCs) doped with Na ions, resulting in NCs with a monodisperse state, homogeneous morphology, and good crystallinity. By adjusting the amount of Na+ doping, the band gap of the NCs was significantly increased from 2.57 eV to 3.00 eV. Furthermore, the relatively low value of photoluminescence quantum yield (PLQY) in the original Cs2AgBiBr6 NCs (∼0.5%) was increased to about 8.5% when doped with 60% Na+. Additionally, the exciton lifetime of the NCs was extended to 16.15 ns compared to the original 2 ns. As a result, the doping of Na + significantly enhanced the PLQY of Cs2AgBiBr6 NCs, indicating their potential value for use in optoelectronic devices.

Enhanced femtosecond nonlinear optical response in Mn-doped Cs2AgInCl6 nanocrystals.

Lead-free halide double perovskite nanocrystals (DPNCs) are emerging materials, recently explored as potential candidates in light-emitting, photovoltaic, and other optoelectronic applications. This Letter reveals unusual photophysical phenomena and nonlinear optical (NLO) properties of Mn-doped Cs2AgInCl6 nanocrystals (NCs) via temperature-dependent photoluminescence (PL) and femtosecond Z-scan measurements. The PL emission measurements suggest that self-trapped excitons (STEs) are present, and more than one STE state is possible for this doped double perovskite. We observed enhanced NLO coefficients, owing to the improved crystallinity arising from the Mn doping. From the closed aperture Z-scan data, we have calculated two fundamental parameters, Kane energy (29 eV) and exciton reduced mass (0.22m0). We further obtained the optical limiting onset (1.84 mJ/cm2) and figure of merit as a proof-of-concept application to demonstrate the potential in optical limiting and optical switching applications. Highlighting the self-trapped excitonic emission and NLO applications, the multifunctionality of this material system is demonstrated. This investigation provides an avenue to design novel photonic and nonlinear optoelectronic devices.

Improved optical properties of lead-free double perovskite Cs2NaBiCl6 nanocrystal via K ions doping

Double perovskite has shown great potential to solve the toxicity and instability problems of lead halide perovskite in practical applications. However, most lead-free double perovskite nanocrystals have low photoluminescence quantum yield (PLQY). Metal ion doping is usually an effective method to improve the optical properties of lead-free double perovskite nanocrystals (NCs). Here, we have prepared monodisperse Cs2NaBiCl6 NCs with uniform morphology and good crystallinity, and a series of Cs2NaBiCl6 NCs with different K+ doping amounts were prepared by colloid synthesis strategy. As the amount of potassium ion doping increased, the absorption spectra of the perovskites shifted towards the red, and the bandgap decreased from 3.56 eV to 3.50 eV. At the same time, the introduction of K+ improved the optical properties of Cs2NaBiCl6 NCs. The PLQY of Cs2Na0.62K0.38BiCl6 NCs reached 7.06 %, which was 4.38 times higher than that of Cs2NaBiCl6 NCs. The lifetime of exciton was increased from 3.42 ns to 12.02 ns by 3.5 times. Thermogravimetric analysis showed that Cs2Na0.62K0.38BiCl6 NCs had better thermal stability than Cs2NaBiCl6 NCs. Temperature-dependent PL spectra showed that Cs2Na0.62K0.38BiCl6 had higher exciton binding energy and longitudinal optical phonon energy than Cs2NaBiCl6 NCs.

Highly Selective Photosynthesis of Formic Acid by Unifying the Products of CO2 Reduction and Methanol Oxidation

Photocatalytic conversion of CO2 to added‐value fuels or chemicals is a promising technology for the effective utilization of the disturbing greenhouse gas, but its economic benefit is limited either by low efficiency due to the difficulty of water oxidation or by the employment of expensive sacrificial reagents. To overcome this dilemma, herein, an effective strategy is reported for the resourceful utilization of CO2 by creating an eco‐friendly bifunctional photocatalyst to achieve CO2 photoreduction concurrent with methanol photooxidation to the uniform product of formic acid for the first time. The bifunctional photocatalyst is elaborately constructed by in situ encapsulating lead‐free double perovskite (Cs2AgBiBr6, abbreviated as CABB) nanocrystals into the pores of Fe‐based metal−organic framework (MIL‐101(Fe)). The tight contact between CABB and MIL‐101(Fe) in the resultant CABB/MIL‐101(Fe) composite facilitates the efficient spatial separation of photogenerated carriers, which leads to the division of reduction and oxidation functional units. CABB/MIL‐101(Fe) composites can unify the redox products into formic acid, reaching an impressive formation yield of 1375 μmol g−1 h−1 with a high selectivity of 97.8%. This work provides a viable strategy for the efficient photosynthesis of formic acid, promoting the cost‐effective utilization of CO2.

Incorporation sodium ions into monodisperse lead-free double perovskite Cs2AgBiCl6 nanocrystals to improve optical properties

Lead-free double perovskite nanocrystals (NCs) have emerged as a promising candidate in the optical field, owing to their non-toxic, good moist heat and chemical stability. However, their poor optical properties limited their application. To improve the optical properties of lead-free double perovskite NCs, metal ion doping or alloying had been suggested as a promising strategy. Here, we prepared monodisperse, uniformly sized, cubic morphology of Cs2AgBiCl6 NCs with different Na+ incorporation amounts via a simple hot-injection method. The Na+ incorporation broke the parity-forbidden transition by reducing the inversion symmetry of the electron wave function at the Ag site, which changed the parity of the self-trapped exciton wave function and thus allowed radiative recombination. As a result, the photoluminescence quantum yield (PLQY) of Na+-alloyed Cs2AgBiCl6 NCs (12.1%) was higher than that of Cs2AgBiCl6 NCs (2.4%), and the exciton lifetime of Na+-alloyed Cs2AgBiCl6 NCs increased to 36.98 ns from 17.58 ns for Cs2AgBiCl6 NCs. By adjusting the amount of Na+ incorporation, the band gap of Cs2AgBiCl6 NCs can be significantly tuned from ∼2.90 eV to ∼3.50 eV. Furthermore, the temperature-dependent photoluminescence spectra indicated that the Na+-alloyed Cs2AgBiCl6 NCs possessed higher longitudinal optical phonon energy and exciton binding energy compared to Cs2AgBiCl6 NCs. This suggested that there were strong exciton-phonon interactions during exciton recombination, a reduced probability of non-radiative processes, and excellent thermal stability. It offers a promising strategy for improving the optical properties of lead-free double perovskite NCs, and have the potential to replace traditional lead halide perovskite NCs in future optoelectronic applications.

Lanthanide Double Perovskite Nanocrystals with Emissions Covering the UV‐C to NIR Spectral Range

AbstractLead halide perovskite nanocrystals (NCs) have recently drawn considerable attention in the fields of materials science and nanotechnology. However, a major drawback of these NCs is the reliance on toxic lead, which hinders widespread application. Herein, a new class of lead‐free perovskite NCs, that is, lanthanide double perovskite (Ln‐DP) NCs, with f‐orbital‐induced optical properties, is introduced. The Pr‐, Ce‐, Tb‐, Eu‐, Sm‐, and Yb‐based Ln‐DP NCs display narrow d→f and f→f emissions ranging from the UV‐C to the near‐infrared spectral region. Experimental data and calculations reveal that the emissive Ln‐DP NCs exhibit small molecule‐like electronic absorptions: f→d atomic transitions or ligand‐to‐metal charge transfer transitions. Last, it is demonstrated that by alloying Ln compositions in the DP NCs, new materials with unique and improved optical properties can be obtained. These Ln‐DP NCs are promising for optical sensing and lighting, and as components in optoelectronic and/or magneto‐fluorescent devices.

Room-temperature synthesis of lead-free copper(I)-antimony(III)-based double perovskite nanocrystals

In the field of perovskite solar cells, explorations of new lead-free all-inorganic perovskite materials are of great interest to address the instability and toxicity issues of lead-based hybrid perovskites. Recently, copper-antimony-based double perovskite materials have been reported with ideal band gaps, which possess great potential as absorbers for photovoltaic applications. Here, we synthesize Cs2CuSbCl6 double perovskite nanocrystals (DPNCs) at ambient conditions by a facile and fast synthesis method, namely, a modified ligand-assisted reprecipitation method. We choose methanol as a solvent for precursor salts as it is less toxic and easily removed in contrast to widely used dimethylformamide. Our computational structure search shows that the Cs2CuSbCl6 structure containing alternating [CuCl6]5− and [SbCl6]3− octahedral units is a metastable phase that is 30 meV/atom higher in energy compared to the ground state structure with [CuCl3]2− and [SbCl6]3− polyhedra. However, this metastable Cs2CuSbCl6 double perovskite structure can be stabilized through solution-based nanocrystal synthesis. Using an anion-exchange method, Cs2CuSbBr6 DPNCs are obtained for the first time, featuring a narrow bandgap of 0.9 eV. Finally, taking advantage of the solution processability of DPNCs, smooth and dense Cs2CuSbCl6 and Cs2CuSbBr6 DPNC films are successfully fabricated.

Two-Dimensional Cs2 AgInx Bi1-x Cl6 Alloyed Double Perovskite Nanoplatelets for Solution-Processed Light-Emitting Diodes.

Lead-free double perovskites have emerged as a promising class of materials with potential to be integrated into a wide range of optical and optoelectronic applications. Herein, we demonstrate the first synthesis of two-dimensional (2D) Cs2 AgInx Bi1-x Cl6 (0 ≤ x ≤ 1) alloyed double perovskite nanoplatelets (NPLs) with well controlled morphology and composition. The obtained NPLs show unique optical properties with the highest photoluminescence quantum yield of 40.1%. Both temperature dependent spectroscopic studies and density functional theory calculation results reveal that the morphological dimension reduction and In-Bi alloying effect together boost the radiative pathway of the self-trapped excitons of the alloyed double perovskite NPLs. Moreover, the NPLs exhibit good stability under ambient conditions and against polar solvents, which is ideal for all solution-processing of the materials in low-cost device manufacturing. We demonstrate the first solution-processed light-emitting diodes using the Cs2 AgIn0.9 Bi0.1 Cl6 alloyed double perovskite NPLs as the sole emitting component, showing luminance maximum of 58cd/m2 and peak current efficiency of 0.013cd/A. Our study sheds light on morphological control and composition-property relationships of double perovskite nanocrystals, paving the way toward ultimate utilizations of lead-free perovskite materials in diverse sets of real-life applications. This article is protected by copyright. All rights reserved.

Improved Optical Properties of Lead‐Free Double Perovskite Cs2AgBiBr6 Nanocrystals via Na Ions Doping

AbstractLead‐free double perovskite nanocrystals (NCs) are a promising alternative to lead‐based perovskite NCs for optoelectronic materials due to their nontoxic and good moist‐thermal stability. However, most of the lead‐free double perovskite NCs exhibit unsatisfying photoluminescence quantum yield (PLQY); the metal ions doping is an effective method to improve the optical properties. Here, monodisperse, homogeneous cubic morphology of Na+‐doped Cs2AgBiBr6 NCs is prepared via a colloidal synthesis strategy. When Na+ is doped into Cs2AgBiBr6 NCs, the inversion‐symmetry‐induced parity‐forbidden transition is broken. So, the wave function parity of the self‐trapped excitons at Ag atoms is changed, which allows the radiative transition to occur. This leads to a higher PLQY for Na+‐doped Cs2AgBiBr6 NCs (9.08%) than that for Cs2AgBiBr6 NCs (0.40%), and the exciton lifetime is extended from 1.87 ns for Cs2AgBiBr6 NCs to 17.15 ns for Na+‐doped Cs2AgBiBr6 NCs. The Na+ doping elevates the longitudinal optical phonon energy and exciton binding energy, which results in weaker nonradiative transitions during exciton recombination and improved NC thermal stability. So, the Na+‐doped Cs2AgBiBr6 NCs maybe possess potentially valuable applications in optoelectronic devices.

A robotic platform for the synthesis of colloidal nanocrystals

Morphological control with broad tunability is a primary goal for the synthesis of colloidal nanocrystals with unique physicochemical properties. Here we develop a robotic platform as a substitute for trial-and-error synthesis and labour-intensive characterization to achieve this goal. Gold nanocrystals (with strong visible-light absorption) and double-perovskite nanocrystals (with photoluminescence) are selected as typical proof-of-concept nanocrystals for this platform. An initial choice of key synthesis parameters was acquired through data mining of the literature. Automated synthesis and in situ characterization with further ex situ validation was then carried out and controllable synthesis of nanocrystals with the desired morphology was accomplished. To achieve morphology-oriented inverse design, correlations between the morphologies and structure-directing agents are identified by machine-learning models trained on a continuously expanded experimental database. Thus, the developed robotic platform with a data mining–synthesis–inverse design framework is promising in data-driven robotic synthesis of nanocrystals and beyond.

Room temperature synthesis of double perovskite Cs2AlBiCl6 for photovoltaic applications

Toxicity and stability issue in lead halide inorganic perovskite nanomaterial can be solved with the help of lead free double perovskite (DP) nanocrystals (NCs). Herein, we have synthesized a new halide double perovskite material Cs2AlBiCl6 for the first time and explored its structural and optical properties which further shows remarkable similarities to lead induced compounds. Also, in this article we have demonstrated the solar cell device based on the synthesized material showing power conversion efficiency of 1.965% which is remarkable and comparable to the single perovskites based solar cell devices. This material is showing promising absorbance phenomenon with a direct and indirect band gap of 3.23 eV and 2.63 eV respectively with excellent stability under ambient condition. The formation of synthesized double perovskite phase has been confirmed using X-ray powder diffraction (XRD) which results into a high purity and good crystallinity of the material. The temperature dependent photoluminescence (TDPL) phenomenon from 19 K to 300 K has been recorded to understand the luminescent behavior of the material. An excellent photoluminescence has been observed due to self-trapped exciton (STE) emission attributed to the distortion in the lattice. A decrease in intensity with increase in temperature has been observed due to conversion of excitons into free carriers with the help of thermal energy. This novel experimental study suggest the utility of Cs2AlBiCl6 as a stable and green alternatives for optoelectronic applications and provide a broad and undiscovered compositional space for finding promising semiconducting materials for optoelectronic and photovoltaic devices applications.

Tb3+ and Bi3+ Co-Doping of Lead-Free Cs2NaInCl6 Double Perovskite Nanocrystals for Tailoring Optical Properties.

Lead halide perovskites have achieved remarkable success in various photovoltaic and optoelectronic applications, especially solar cells and light-emitting diodes (LEDs). Despite the significant advances of lead halide perovskites, lead toxicity and insufficient stability limit their commercialization. Lead-free double perovskites (DPs) are potential materials to address these issues because of their non-toxicity and high stability. By doping DP nanocrystals (NCs) with lanthanide ions (Ln3+), it is possible to make them more stable and impart their optical properties. In this work, a variable temperature hot injection method is used to synthesize lead-free Tb3+-doped Cs2NaInCl6 DP NCs, which exhibit a major narrow green photoluminescence (PL) peak at 544 nm derived from the transition of Tb3+ 5D4→7F5. With further Bi3+ co-doping, the Tb3+-Bi3+-co-doped Cs2NaInCl6 DP NCs are not only directly excited at 280 nm but are also excited at 310 nm and 342 nm. The latter have a higher PL intensity because partial Tb3+ ions are excited through more efficient energy transfer channels from the Bi3+ to the Tb3+ ions. The investigation of the underlying mechanism between the intrinsic emission of Cs2NaInCl6 NCs and the narrow green PL caused by lanthanide ion doping in this paper will facilitate the development of lead-free halide perovskite NCs.