Herein, we develop an effective approach for incorporating lead (Pb) ions into manganese (Mn) halide perovskite-analogue nanocrystals (PA NCs) of CsMn­(Cl/Br)3·2H2O via room-temperature supersaturation recrystallization. Pb2+-incorporated Mn-PA NCs exhibit strong orange emission upon UV light illumination, a peak centered at 600 nm assigned to Mn2+ transition (4T1g → 6A1g) with a photoluminescence quantum yield (PLQY) of 41.8% compared to the pristine Mn-PA NCs with very weak PL (PLQY = 0.10%). The significant enhancement of PLQY is attributed to the formation of [Mn­(Cl/Br)4(OH)2]4––[Pb­(Cl/Br)4(OH)2]4––[Mn­(Cl/Br)4(OH)2]4– chain network structure, in which Pb2+ effectively dilutes the Mn2+ concentration to reduce magnetic coupling between Mn2+ pairs to relax the spin and parity selection rules. In addition, excited energy can effectively transfer from the [Pb­(Cl/Br)4(OH)2]4– unit to Mn2+ luminescence centers owing to the low activation energy. Pb2+-incorporated PA NCs also exhibit excellent stability. The combined strong PL and high stability make Pb2+-incorporated Mn-based PA NCs an excellent candidate for potential optronic applications.

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.

Zero-dimensional (0D) all-inorganic cesium lead halide perovskites, particularly Cs4PbBr6, have been attracting wide attention due to their excellent optical properties and stability. The research also focuses on the origin of green emission from Cs4PbBr6 which has a bandgap located at UVB region. From now on, both Cs4PbBr6 without visible emission and with green emission have been successfully prepared, however, the origin of green emission remains controversial. Photocurrent response is one of the effective approaches to explore how the photo-excited carriers influence the photo-physical properties of materials. In our study, Cs4PbBr6 particles without visible emission and with green emission were synthesized and their photocurrent response was investigated. The former showed positive photocurrent response, while the latter showed negative photocurrent response. The negative response was believed to be due to a built-in electric field constructed by the charged excitons in green-emissive Cs4PbBr6. From our calculation, numerous vacancies of Br is easier to appear in green-emissive Cs4PbBr6 lattice, which could combine the neutral excitons to form charged excitons. This work may contribute to the explanation of the origin of green emission of Cs4PbBr6 to some extent.

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