Abstract:Over the past decade,
lead halide perovskites (LHPs) have emerged
as new promising materials in the fields of photovoltaics and light
emission due to their facile syntheses and exciting optical properties.
The enthusiasm generated by LHPs has inspired research in perovskite-related
materials, including the so-called “zero-dimensional cesium
lead halides”, which will be the focus of this Perspective.
The structure of these materials is formed of disconnected lead halide
octahedra that are stabilized by cesium i… Show more
“…Within the Cs 4 PbBr 6 NCs, the [PbBr 6 ] 4− octahedra are completely decoupled in all dimensions as a result of minimal electronic overlap between the adjacent octahedra. Therefore, the 0D perovskite NC system always exhibits a molecular-like absorption, and the size of the NCs does not have any remarkable effect on the band structure, which is consistent with the report by Manna 8,18 . Meanwhile, this unique structure renders a strong quantum confinement to confine charge carriers inside the octahedra to easily form bound excitons, which is exemplified by the clear and sharp excitonic peak in the absorption spectrum of this material without applied pressure, as shown in Supplementary Fig.…”
Section: Resultssupporting
confidence: 91%
“…Although some works showed that Cs 4 PbBr 6 NCs or the bulk structure possess fluorescence in the visible region 22–24 , an ongoing debate about the origin of the emission for these systems remains. The recent report by Manna et al 8,18 proposed a more reasonable explanation, deepening the insight into the nonfluorescent mechanism of the Cs 4 PbBr 6 systems. According to their reports 8,18 , the origin of PL can be attributed to the presence of 3D perovskite impurities embedded inside the Cs 4 PbBr 6 matrix, rather than to the intrinsic emission of Cs 4 PbBr 6 .Fig.…”
Section: Resultsmentioning
confidence: 90%
“…The recent report by Manna et al 8,18 proposed a more reasonable explanation, deepening the insight into the nonfluorescent mechanism of the Cs 4 PbBr 6 systems. According to their reports 8,18 , the origin of PL can be attributed to the presence of 3D perovskite impurities embedded inside the Cs 4 PbBr 6 matrix, rather than to the intrinsic emission of Cs 4 PbBr 6 .Fig. 1Structural characterization of Cs 4 PbBr 6 NCs.…”
Metal halide perovskites (MHPs) are of great interest for optoelectronics because of their high quantum efficiency in solar cells and light-emitting devices. However, exploring an effective strategy to further improve their optical activities remains a considerable challenge. Here, we report that nanocrystals (NCs) of the initially nonfluorescent zero-dimensional (0D) cesium lead halide perovskite Cs4PbBr6 exhibit a distinct emission under a high pressure of 3.01 GPa. Subsequently, the emission intensity of Cs4PbBr6 NCs experiences a significant increase upon further compression. Joint experimental and theoretical analyses indicate that such pressure-induced emission (PIE) may be ascribed to the enhanced optical activity and the increased binding energy of self-trapped excitons upon compression. This phenomenon is a result of the large distortion of [PbBr6]4− octahedral motifs resulting from a structural phase transition. Our findings demonstrate that high pressure can be a robust tool to boost the photoluminescence efficiency and provide insights into the relationship between the structure and optical properties of 0D MHPs under extreme conditions.
“…Within the Cs 4 PbBr 6 NCs, the [PbBr 6 ] 4− octahedra are completely decoupled in all dimensions as a result of minimal electronic overlap between the adjacent octahedra. Therefore, the 0D perovskite NC system always exhibits a molecular-like absorption, and the size of the NCs does not have any remarkable effect on the band structure, which is consistent with the report by Manna 8,18 . Meanwhile, this unique structure renders a strong quantum confinement to confine charge carriers inside the octahedra to easily form bound excitons, which is exemplified by the clear and sharp excitonic peak in the absorption spectrum of this material without applied pressure, as shown in Supplementary Fig.…”
Section: Resultssupporting
confidence: 91%
“…Although some works showed that Cs 4 PbBr 6 NCs or the bulk structure possess fluorescence in the visible region 22–24 , an ongoing debate about the origin of the emission for these systems remains. The recent report by Manna et al 8,18 proposed a more reasonable explanation, deepening the insight into the nonfluorescent mechanism of the Cs 4 PbBr 6 systems. According to their reports 8,18 , the origin of PL can be attributed to the presence of 3D perovskite impurities embedded inside the Cs 4 PbBr 6 matrix, rather than to the intrinsic emission of Cs 4 PbBr 6 .Fig.…”
Section: Resultsmentioning
confidence: 90%
“…The recent report by Manna et al 8,18 proposed a more reasonable explanation, deepening the insight into the nonfluorescent mechanism of the Cs 4 PbBr 6 systems. According to their reports 8,18 , the origin of PL can be attributed to the presence of 3D perovskite impurities embedded inside the Cs 4 PbBr 6 matrix, rather than to the intrinsic emission of Cs 4 PbBr 6 .Fig. 1Structural characterization of Cs 4 PbBr 6 NCs.…”
Metal halide perovskites (MHPs) are of great interest for optoelectronics because of their high quantum efficiency in solar cells and light-emitting devices. However, exploring an effective strategy to further improve their optical activities remains a considerable challenge. Here, we report that nanocrystals (NCs) of the initially nonfluorescent zero-dimensional (0D) cesium lead halide perovskite Cs4PbBr6 exhibit a distinct emission under a high pressure of 3.01 GPa. Subsequently, the emission intensity of Cs4PbBr6 NCs experiences a significant increase upon further compression. Joint experimental and theoretical analyses indicate that such pressure-induced emission (PIE) may be ascribed to the enhanced optical activity and the increased binding energy of self-trapped excitons upon compression. This phenomenon is a result of the large distortion of [PbBr6]4− octahedral motifs resulting from a structural phase transition. Our findings demonstrate that high pressure can be a robust tool to boost the photoluminescence efficiency and provide insights into the relationship between the structure and optical properties of 0D MHPs under extreme conditions.
“…Controversial results on the physical properties of Cs 4 PbBr 6 have been reported recently, with some claiming that it has intrinsic green emission, and others believing it is non-emissive in the visible wavelength. A recent perspective by Manna et al has provided detailed discusses on the contrasting opinions on the properties, and suggested that defect-free Cs 4 PbBr 6 has an intrinsic large band gap of > 3.2 eV and the green emission of those Cs 4 PbBr 6 materials is likely from contamination by CsPbBr 3 nanocrystal-like impurities [131]. To our point of view, Cs 4 PbBr 6 cannot be considered as 'true' 0D structure, because the Cs + cations are too small to have individual metal halide octahedra completely isolated from each other without electronic band formation.…”
Organic-inorganic metal halide hybrids have emerged as new generation functional materials with exceptional structure and property tunability for a variety of applications. Besides the most investigated ABX 3 metal halide perovskites, a variety of hybrids consisting of a wide range of organic cations and metal halide anions have been developed and studied recently. Here, we provide an overview of these new materials possessing various crystallographic structures, including double perovskites, low dimensional hybrids, and other perovskite-related materials. We discuss their syntheses, functional properties, and optoelectronic applications. Challenges and opportunities are then laid out for these hybrid materials beyond perovskites.
IMPACT STATEMENTBy choosing appropriate organic cations and metal halide anions, single crystalline ionically bonded hybrid materials can be assembled to possess various structures beyond the well-known ABX 3 perovskite. These hybrid materials exhibit exciting new properties with potential applications in a variety of areas.
ARTICLE HISTORY
“…Therefore, it is more reasonable to deduce that nanosized CsPbBr 3 NCs were formed regardless of the fabrication techniques of Cs 4 PbBr 6 micro or macro crystals. [120] Very recently, we developed a HBr-assisted slow cooling method to fabricate Cs 4 PbBr 6 single crystallites with embedded CsPbBr 3 NCs. [121] as depicted in Figure 8a,b.…”
Section: In Situ Fabricated Pncs Embedded In Crystalline Matrixmentioning
in bulk halide perovskites, long carrier diffusion length, and an absorption range covering the visible solar spectrum, collectively enable the high performance of photo electricity conversion. Compared to the bulk materials, perovskite nanocrystals or quantum dots (usually denoted as PNCs or PQDs) show obvious excitonic features with enhanced photoluminescence (PL) properties due to the well-known size-dependent quantum confinement effects. [14][15][16][17] The combination of color saturated emissions, super high quantum yield (QY), as well as easy processing inspired the intensive exploration of PNCs as light emitters, which is now under spotlights in the field of optical materials.The first perspective aim of PNCs is to alternate the state-of-the-art CdSe or InP quantum dots (QDs) as new generation luminescence materials. [18,19] As shown in Figure 1, these QD materials have been well demonstrated to be potential functional components for photonic and optoelectronic applications, and are currently on the way to industrialization. [20][21][22][23] Specifically, QDs can be employed as fluorescence labels, [24] laser gain media, [25] LED phosphors, [26] and down-shifting films for LCD backlights. [27,28] They can also be processed into thin film for optoelectronic devices including solar cells, [29] photodetectors, [30,31] transistors [32] and LEDs. [33] The PNCs outcompete these conventional QDs in terms of narrower full width at half maximum (FWHM) and low fabrication cost, but most importantly, the ease of in situ preparation. [34,35] Herein, this progress report highlight the developments of in situ fabricated PNCs.Colloidal semiconductor QDs are typically synthesized ex situ in flasks by hot injection method, stabilized by surface ligands. [36][37][38][39] To incorporate such solution based materials into applications usually requires purification, redispersion and surface engineering. For instance, ligand exchange is often employed to disperse QDs into aimed solvent, inducing defects that inevitably derogating the PLQYs. [40] Moreover, the organic ligands themselves also suffer from the risk of disabsorbing, reducing the stability of the QDs and thus the final devices. [41] Because halide perovskite are ionic compounds that can be well dissolved into polar solvents, PNCs can be fabricated through either ex situ routes in flask or in situ strategies on substrates. The in situ fabricated PNCs are adaptable to devices integration due to their scalable and low-cost manufacturing. In this regard, more and more efforts have been made in terms of the controlling synthesis, physical properties and device applications of PNC materials.After over 30 years of development, colloidal quantum dots have now become mature luminescent materials in photonic and optoelectronic operations and start to hit the market. The emerging perovskite nanocrystals are expected to promote large-scale commercialization due to their superior optical properties as well as low cost and easy fabrication. This progress report is focused on the...
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