Highly Emissive and Stable Cs₂AgInCl₆ Double Perovskite Nanocrystals by Bi³⁺ Doping and Potassium Bromide Surface Passivation

Abstract

In this study, a facile approach is used to enhance the broad orange emission efficiency and stability as well as monodispersity of Cs 2 AgInCl 6 nanocrystals (NCs) via doping Bi 3+ and surface passivation with potassium bromide. While the pristine Cs 2 AgInCl 6 NCs show an excitonic absorption peak at 280 nm, the doped NCs have an additional absorption peak at 365 nm, which is attributed to direct bismuth s−p transition. Compared to the low photoluminescence (PL) quantum yield (QY) of 0.04% for the pristine Cs 2 AgInCl 6 NCs due to parity forbidden transition, the doped NCs show a PLQY of 5.82%, a significant improvement due to breaking of the parity forbidden transition. The PLQY can be further increased to 8.59% for Cs 2 AgIn 0.9 Bi 0.1 Cl 6 when passivated with KBr. This work demonstrates that the combination of doping and surface passivation can substantially improve the PL of the Cs 2 AgInCl 6 double perovskite. A model is proposed to explain the observed enhancement in PL and stability.

Enhanced Photoluminescence of All-Inorganic Manganese Halide Perovskite-Analogue Nanocrystals by Lead Ion Incorporation

“…The fast PL decay component for Pb 2+ -incorporated PA NCs is 1.18 ns and the slow component is 6.90 ns, giving an average lifetime of 2.21 ns. On the basis of the PLQY and average lifetime, we can calculate the radiative and nonradiative lifetime using the relationships between observed lifetime (τ obs ), radiative lifetime (τ r ), nonradiative lifetime (τ nr ) and PLQY: 48 PLQY / obs r τ τ =…”

“…The fast PL decay component for Pb 2+ -incorporated PA NCs is 1.18 ns and the slow component is 6.90 ns, giving an average lifetime of 2.21 ns. On the basis of the PLQY and average lifetime, we can calculate the radiative and nonradiative lifetime using the relationships between observed lifetime (τ obs ), radiative lifetime (τ r ), nonradiative lifetime (τ nr ) and PLQY: With the Mn:Pb ratio changed from 1:0.17 to 1:0.25, the radiative lifetime of Pb 2+ emission becomes shorter while the nonradiative lifetime remains about the same, leading to the increased PLQY (9.64%) of Pb 2+ . Subsequently, as the Mn:Pb ratio was changed to 1:0.50, the nonradiative lifetime becomes longer while the radiative lifetime remains about the same, which is consistent with the higher PLQY (15.92%).…”

Competing Energy Transfer-Modulated Dual Emission in Mn2+-Doped Cs2NaTbCl6 Rare-Earth Double Perovskites

“…However, such a replacement would cause a reduction in dimensionality and charge imbalance if only the trivalent ions are used. − Based on isoelectronic theory, this issue can be addressed by using a proper monovalent cation in conjunction with trivalent ions to generate double perovskites A 2 M I M III X 6 (A = Cs; M I = Na, K, Ag; M III = Bi, In, and Sb, and X = Cl, Br, I). However, most lead-free double perovskites exhibit low photoluminescence (PL) due to indirect bandgap or parity forbidden transitions. − Through appropriate ion doping or alloying, the bandgap of double perovskites can be altered or their structural symmetry can be broken, which can break the partial forbidden transition and thereby enhance their optical properties. , Various dopants, such as Sb 3+ , Mn 2+ , and Ln 3+ , have been studied for doping double perovskites. − …”

“…31−34 Through appropriate ion doping or alloying, the bandgap of double perovskites can be altered or their structural symmetry can be broken, which can break the partial forbidden transition and thereby enhance their optical properties. 35,36 Various dopants, such as Sb 3+ , Mn 2+ , and Ln 3+ , have been studied for doping double perovskites. 37−42 Lanthanide ions have a rich 4f n electron configuration and possess the shielding effect of the outermost 5s 2 5p 6 full-layer electrons.…”

Solid state nuclear magnetic resonance studies of functional materials

“…This observation is consistent with recent reports of the surface passivation of Cs 2 AgInCl 6 and Cs 2 In 0.9 Bi 0.1 AgCl 6 nanocrystals using low levels of K + cations introduced as KBr. [221] The GIPAW DFT calculated 39 K chemical shift distributions shown in Figures 6.8(d) suggest that significant overlap influences both the A and B site shift ranges, precluding chemical resolution of the constituent cubic and monoclinic phases in each case. However, more importantly, the distinct resolution between the A and B site chemical shift ranges demonstrates that the K + substitution levels into this nanocrystal series (particularly at the higher incorporation levels) is dominated by A site occupancy by a factor of ∼2 -4:1.…”