共查询到20条相似文献,搜索用时 15 毫秒
1.
《Angewandte Chemie (International ed. in English)》2017,56(41):12471-12475
Lead‐based perovskite nanocrystals (NCs) have outstanding optical properties and cheap synthesis conferring them a tremendous potential in the field of optoelectronic devices. However, two critical problems are still unresolved and hindering their commercial applications: one is the fact of being lead‐based and the other is the poor stability. Lead‐free all‐inorganic perovskite Cs3Bi2X9 (X=Cl, Br, I) NCs are synthesized with emission wavelength ranging from 400 to 560 nm synthesized by a facile room temperature reaction. The ligand‐free Cs3Bi2Br9 NCs exhibit blue emission with photoluminescence quantum efficiency (PLQE) about 0.2 %. The PLQE can be increased to 4.5 % when extra surfactant (oleic acid) is added during the synthesis processes. This improvement stems from passivation of the fast trapping process (2–20 ps). Notably, the trap states can also be passivated under humid conditions, and the NCs exhibited high stability towards air exposure exceeding 30 days. 相似文献
2.
Bin Yang Feng Hong Junsheng Chen Yuxuan Tang Li Yang Youbao Sang Xusheng Xia Jingwei Guo Haixiang He Songqiu Yang Weiqiao Deng Keli Han 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(8):2300-2305
A series of lead‐free double perovskite nanocrystals (NCs) Cs2AgSb1?yBiyX6 (X: Br, Cl; 0≤y≤1) is synthesized. In particular, the Cs2AgSbBr6 NCs is a new double perovskite material that has not been reported for the bulk form. Mixed Ag–Sb/Bi NCs exhibit enhanced stability in colloidal solution compared to Ag–Bi or Ag–Sb NCs. Femtosecond transient absorption studies indicate the presence of two prominent fast trapping processes in the charge‐carrier relaxation. The two fast trapping processes are dominated by intrinsic self‐trapping (ca. 1–2 ps) arising from giant exciton–phonon coupling and surface‐defect trapping (ca. 50–100 ps). Slow hot‐carrier relaxation is observed at high pump fluence, and the possible mechanisms for the slow hot‐carrier relaxation are also discussed. 相似文献
3.
Bin Yang Junsheng Chen Songqiu Yang Feng Hong Lei Sun Peigeng Han Prof. Dr. Tõnu Pullerits Prof. Dr. Weiqiao Deng Prof. Dr. Keli Han 《Angewandte Chemie (International ed. in English)》2018,57(19):5359-5363
Lead‐free perovskite nanocrystals (NCs) were obtained mainly by substituting a Pb2+ cation with a divalent cation or substituting three Pb2+ cations with two trivalent cations. The substitution of two Pb2+ cations with one monovalent Ag+ and one trivalent Bi3+ cations was used to synthesize Cs2AgBiX6 (X=Cl, Br, I) double perovskite NCs. Using femtosecond transient absorption spectroscopy, the charge carrier relaxation mechanism was elucidated in the double perovskite NCs. The Cs2AgBiBr6 NCs exhibit ultrafast hot‐carrier cooling (<1 ps), which competes with the carrier trapping processes (mainly originate from the surface defects). Notably, the photoluminescence can be increased by 100 times with surfactant (oleic acid) added to passivate the defects in Cs2AgBiCl6 NCs. These results suggest that the double perovskite NCs could be potential materials for optoelectronic applications by better controlling the surface defects. 相似文献
4.
Peigeng Han Xin Mao Songqiu Yang Fei Zhang Bin Yang Donghui Wei Weiqiao Deng Keli Han 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(48):17391-17395
Lead‐free halide perovskite nanocrystals (NCs) have drawn wide attention for solving the problem of lead perovskites toxicity and instability. Herein, we synthesize the direct band gap double perovskites undoped and Ag‐doped Cs2NaInCl6 NCs by variable temperature hot injection. The Cs2NaInCl6 NCs have little photoluminescence because of dark self‐trapped excitons (STEs). The dark STEs can be converted into bright STEs by doping with Ag+ to produce a bright yellow emission, with the highest photoluminescence quantum efficiency of 31.1 %. The dark STEs has been directly detected experimentally by ultrafast transient absorption (TA) techniques. The dynamics mechanism is further studied. In addition, the Ag‐doped NCs show better stability than the undoped ones. This result provides a new way to enhance the optical properties of lead‐free perovskites NCs for high‐performance light emitters. 相似文献
5.
Meiying Leng Zhengwu Chen Ying Yang Zha Li Kai Zeng Kanghua Li Guangda Niu Yisu He Qingchao Zhou Jiang Tang 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2016,128(48):15236-15240
Lead halide perovskite quantum dots (QDs) are promising candidates for future lighting applications, due to their high quantum yield, narrow full width at half maximum (FWHM), and wide color gamut. However, the toxicity of lead represents a potential obstacle to their utilization. Although tin(II) has been used to replace lead in films and QDs, the high intrinsic defect density and oxidation vulnerability typically leads to unsatisfactory material properties. Bismuth, with much lower toxicity than lead, is promising to constitute lead‐free perovskite materials because Bi3+ is isoelectronic to Pb2+ and more stable than Sn2+. Herein we report, for the first time, the synthesis and optical characterization of MA3Bi2Br9 perovskite QDs with photoluminescence quantum yield (PLQY) up to 12 %, which is much higher than Sn‐based perovskite nanocrystals. Furthermore, the photoluminescence (PL) peaks of MA3Bi2X9 QDs could be easily tuned from 360 to 540 nm through anion exchange. 相似文献
6.
Bin Yang Feng Hong Junsheng Chen Yuxuan Tang Li Yang Youbao Sang Xusheng Xia Jingwei Guo Haixiang He Songqiu Yang Weiqiao Deng Keli Han 《Angewandte Chemie (International ed. in English)》2019,58(8):2278-2283
A series of lead‐free double perovskite nanocrystals (NCs) Cs2AgSb1?yBiyX6 (X: Br, Cl; 0≤y≤1) is synthesized. In particular, the Cs2AgSbBr6 NCs is a new double perovskite material that has not been reported for the bulk form. Mixed Ag–Sb/Bi NCs exhibit enhanced stability in colloidal solution compared to Ag–Bi or Ag–Sb NCs. Femtosecond transient absorption studies indicate the presence of two prominent fast trapping processes in the charge‐carrier relaxation. The two fast trapping processes are dominated by intrinsic self‐trapping (ca. 1–2 ps) arising from giant exciton–phonon coupling and surface‐defect trapping (ca. 50–100 ps). Slow hot‐carrier relaxation is observed at high pump fluence, and the possible mechanisms for the slow hot‐carrier relaxation are also discussed. 相似文献
7.
Zhenzhen Zhang Yongqi Liang Hanlin Huang Xingyi Liu Qi Li Langxing Chen Dongsheng Xu 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(22):7341-7345
Composition engineering of halide perovskite allows the tunability of the band gap over a wide range so that photons can be effectively harvested, an aspect that is of critical importance for increasing the efficiency of photocatalysis under sunlight. However, the poor stability and the low photocatalytic activity of halide perovskites prevent use of these defect‐tolerant materials in wide applications involving photocatalysis. Here, an alcohol‐based photocatalytic system for dye degradation demonstrated high stability through the use of double perovskite of Cs2AgBiBr6. The reaction rate on Cs2AgBiBr6 is comparable to that on CdS, a model inorganic semiconductor photocatalyst. The fact of fast reaction between free radicals and dye molecules indicates the unique catalytic properties of the Cs2AgBiBr6 surface. Deposition of metal clusters onto Cs2AgBiBr6 effectively enhances the photocatalytic activity. Although the stability (five consecutive photocatalytic cycles without obvious decrease of efficiency) requires further improvements, the results indicate the significant potential of Cs2AgBiBr6‐based photocatalysis. 相似文献
8.
Kaushik Kundu Paribesh Acharyya Krishnendu Maji Ranjan Sasmal Sarit S. Agasti Kanishka Biswas 《Angewandte Chemie (International ed. in English)》2020,59(31):13093-13100
Two‐dimensional (2D) lead‐free halide perovskites have generated enormous perception in the field of optoelectronics due to their fascinating optical properties. However, an in‐depth understanding on their shape‐controlled charge‐carrier recombination dynamics is still lacking, which could be resolved by exploring the photoluminescence (PL) blinking behaviour at the single‐particle level. Herein, we demonstrate, for the first time, the synthesis of nanocrystals (NCs) and 2D nanosheets (NSs) of layered mixed halide, Cs3Bi2I6Cl3, by solution‐based method. We applied fluorescence microscopy and super‐resolution optical imaging at single‐particle level to investigate their morphology‐dependent PL properties. Narrow emission line widths and passivation of non‐radiative defects were evidenced for 2D layered nanostructures, whereas the activation of shallow trap states was recognized at 77 K. Interestingly, individual NCs were found to display temporal intermittency (blinking) in PL emission. On the other hand, NS showed temporal PL intensity fluctuations within localized domains of the crystal. In addition, super‐resolution optical image of the NS from localization‐based method showed spatial inhomogeneity of the PL intensity within perovskite crystal. 相似文献
9.
Ying Liu Ximing Rong Mingze Li Maxim S. Molokeev Jing Zhao Zhiguo Xia 《Angewandte Chemie (International ed. in English)》2020,59(28):11634-11640
The incorporation of impurity ions or doping is a promising method for controlling the electronic and optical properties and the structural stability of halide perovskite nanocrystals (NCs). Herein, we establish relationships between rare‐earth ions doping and intrinsic emission of lead‐free double perovskite Cs2AgInCl6 NCs to impart and tune the optical performances in the visible light region. Tb3+ ions were incorporated into Cs2AgInCl6 NCs and occupied In3+ sites as verified by both crystallographic analyses and first‐principles calculations. Trace amounts of Bi doping endowed the characteristic emission (5D4→7F6‐3) of Tb3+ ions with a new excitation peak at 368 nm rather than the single characteristic excitation at 290 nm of Tb3+. By controlling Tb3+ ions concentration, the emission colors of Bi‐doped Cs2Ag(In1?xTbx)Cl6 NCs could be continuously tuned from green to orange, through the efficient energy‐transfer channel from self‐trapped excitons to Tb3+ ions. Our study provides the salient features of the material design of lead‐free perovskite NCs and to expand their luminescence applications. 相似文献
10.
《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2018,130(35):11383-11387
Low‐toxicity, air‐stable bismuth‐based perovskite materials are attractive substitutes for lead halide perovskites in photovoltaic and optoelectronic devices. The structural, optical, and electrical property changes of zero‐dimensional perovskite Cs3Bi2I9 resulting from lattice compression is presented. An emission enhancement under mild pressure is attributed to the increase in exciton binding energy. Unprecedented band gap narrowing originated from Bi−I bond contraction, and the decrease in bridging Bi‐I‐Bi angle enhances metal halide orbital overlap, thereby breaking through the Shockley–Queisser limit under relatively low pressure. Pressure‐induced structural evolutions correlate well with changes in optical properties, and the changes are reversible upon decompression. Considerable resistance reduction implies a semiconductor‐to‐conductor transition at ca. 28 GPa, and the final confirmed metallic character by electrical experiments indicates a wholly new electronic property. 相似文献
11.
Ruiling Zhang Xin Mao Yang Yang Songqiu Yang Wenyuan Zhao Tuerdi Wumaier Donghui Wei Weiqiao Deng Keli Han 《Angewandte Chemie (International ed. in English)》2019,58(9):2725-2729
Lead‐free zero‐dimensional (0D) organic‐inorganic metal halide perovskites have recently attracted increasing attention for their excellent photoluminescence properties and chemical stability. Here, we report the synthesis and characterization of an air‐stable 0D mixed metal halide perovskite (C8NH12)4Bi0.57Sb0.43Br7?H2O, in which individual [BiBr6]3? and [SbBr6]3? octahedral units are completely isolated and surrounded by the large organic cation C8H12N+. Upon photoexcitation, the bulk crystals exhibit ultra‐broadband emission ranging from 400 to 850 nm, which originates from both free excitons and self‐trapped excitons. This is the first example of 0D perovskites with broadband emission spanning the entire visible spectrum. In addition, (C8NH12)4Bi0.57Sb0.43Br7?H2O exhibits excellent humidity and light stability. These findings present a new direction towards the design of environmentally‐friendly, high‐performance 0D perovskite light emitters. 相似文献
12.
Ruiling Zhang Xin Mao Yang Yang Songqiu Yang Wenyuan Zhao Tuerdi Wumaier Donghui Wei Weiqiao Deng Keli Han 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(9):2751-2755
Lead‐free zero‐dimensional (0D) organic‐inorganic metal halide perovskites have recently attracted increasing attention for their excellent photoluminescence properties and chemical stability. Here, we report the synthesis and characterization of an air‐stable 0D mixed metal halide perovskite (C8NH12)4Bi0.57Sb0.43Br7?H2O, in which individual [BiBr6]3? and [SbBr6]3? octahedral units are completely isolated and surrounded by the large organic cation C8H12N+. Upon photoexcitation, the bulk crystals exhibit ultra‐broadband emission ranging from 400 to 850 nm, which originates from both free excitons and self‐trapped excitons. This is the first example of 0D perovskites with broadband emission spanning the entire visible spectrum. In addition, (C8NH12)4Bi0.57Sb0.43Br7?H2O exhibits excellent humidity and light stability. These findings present a new direction towards the design of environmentally‐friendly, high‐performance 0D perovskite light emitters. 相似文献
13.
Meiying Leng Zhengwu Chen Ying Yang Dr. Zha Li Kai Zeng Kanghua Li Dr. Guangda Niu Yisu He Qingchao Zhou Prof. Jiang Tang 《Angewandte Chemie (International ed. in English)》2016,55(48):15012-15016
Lead halide perovskite quantum dots (QDs) are promising candidates for future lighting applications, due to their high quantum yield, narrow full width at half maximum (FWHM), and wide color gamut. However, the toxicity of lead represents a potential obstacle to their utilization. Although tin(II) has been used to replace lead in films and QDs, the high intrinsic defect density and oxidation vulnerability typically leads to unsatisfactory material properties. Bismuth, with much lower toxicity than lead, is promising to constitute lead‐free perovskite materials because Bi3+ is isoelectronic to Pb2+ and more stable than Sn2+. Herein we report, for the first time, the synthesis and optical characterization of MA3Bi2Br9 perovskite QDs with photoluminescence quantum yield (PLQY) up to 12 %, which is much higher than Sn‐based perovskite nanocrystals. Furthermore, the photoluminescence (PL) peaks of MA3Bi2X9 QDs could be easily tuned from 360 to 540 nm through anion exchange. 相似文献
14.
Habibul Arfin Jagjit Kaur Tariq Sheikh Sudip Chakraborty Angshuman Nag 《Angewandte Chemie (International ed. in English)》2020,59(28):11307-11311
Bi3+ and lanthanide ions have been codoped in metal oxides as optical sensitizers and emitters. But such codoping is not known in typical semiconductors such as Si, GaAs, and CdSe. Metal halide perovskite with coordination number 6 provides an opportunity to codope Bi3+ and lanthanide ions. Codoping of Bi3+ and Ln3+ (Ln=Er and Yb) in Cs2AgInCl6 double perovskite is presented. Bi3+‐Er3+ codoped Cs2AgInCl6 shows Er3+ f‐electron emission at 1540 nm (suitable for low‐loss optical communication). Bi3+ codoping decreases the excitation (absorption) energy, such that the samples can be excited with ca. 370 nm light. At that excitation, Bi3+‐Er3+ codoped Cs2AgInCl6 shows ca. 45 times higher emission intensity compared to the Er3+ doped Cs2AgInCl6. Similar results are also observed in Bi3+‐Yb3+ codoped sample emitting at 994 nm. A combination of temperature‐dependent (5.7 K to 423 K) photoluminescence and calculations is used to understand the optical sensitization and emission processes. 相似文献
15.
Siping Liu Dr. Bin Yang Dr. Junsheng Chen Prof. Dr. Donghui Wei Dr. Daoyuan Zheng Qingkun Kong Prof. Dr. Weiqiao Deng Prof. Dr. Keli Han 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(49):22109-22113
Thermally activated delayed fluorescence (TADF) is generally observed in solid-state organic molecules or metal-organic complexes. However, TADF in all-inorganic colloidal nanocrystals (NCs) is rare. Herein, we report the first colloidal synthesis of an air-stable all-inorganic lead-free Cs2ZrCl6 perovskite NCs. The Cs2ZrCl6 NCs exhibit long-lived triplet excited state (138.2 μs), and feature high photoluminescence (PL) quantum efficiency (QY=60.37 %) due to TADF mechanism. The emission color can be easily tuned from blue to green by synthesizing the mixed-halide Cs2ZrBrxCl6−x (0≤x≤1.5) NCs. Femtosecond transient absorption and temperature dependent PL measurements are performed to clarify the emission mechanism. In addition, Bi3+ ions are successfully doped into Cs2ZrCl6 NCs, which further extends the PL properties. This work not only develops a new lead-free halide perovskite NCs for potential optoelectronic applications, but also offers unique strategies for developing new inorganic phosphors. 相似文献
16.
Pengfei Cheng Lei Sun Lu Feng Songqiu Yang Yang Yang Daoyuan Zheng Yang Zhao Youbao Sang Ruiling Zhang Donghui Wei Weiqiao Deng Keli Han 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(45):16233-16237
Low‐dimensional metal halides have recently attracted extensive attention owing to their unique structure and photoelectric properties. Herein, we report the colloidal synthesis of all‐inorganic low‐dimensional cesium copper halide nanocrystals (NCs) by adopting a hot‐injection approach. Using the same reactants and ligands, but different reaction temperatures, both 1D CsCu2I3 nanorods and 0D Cs3Cu2I5 NCs can be prepared. Density functional theory indicates that the reduced dimensionality in 1D CsCu2I3 compared to 0D Cs3Cu2I5 makes the excitons more localized, which accounts for the strong emission of 0D Cs3Cu2I5 NCs. Subsequent optical characterization reveals that the highly luminescent, strongly Stokes‐shifted broadband emission of 0D Cs3Cu2I5 NCs arises from the self‐trapped excitons. Our findings not only present a method to control the synthesis of low‐dimensional cesium copper halide nanocrystals but also highlight the potential of 0D Cs3Cu2I5 NCs in optoelectronics. 相似文献
17.
Organic ligands play a key role in determining the shape and stability of the perovskite nanocrystals (NCs). However, the ligands often create poor stability and defects through imperfect attachment, in addition to the post synthesis detachment. We developed a novel route to synthesize the ligand?free ambient stable two?dimensional (2D) cesium antimony chloride (Cs3Sb2Cl9) NCs. First, hexagonal shape NCs are synthesized through a fast one?step reaction at room temperature using a reprecipitation method. The shape of hexagonal NCs is further tuned into well?defined 2D plates through a solid-state temperature-driven crystal phase transition. In?situ variable temperature X?ray diffraction and differential scanning calorimetry cycles probe temperature-sensitive metastability and irreversibility of trigonal to orthorhombic crystallographic phase transition. Rietveld analyses quantify volume fractions and coherently diffracting crystallite domains that promote the growth of the two crystal phases. Both the hexagonal NCs and plates show ambient structural stability for over months. The proposed formation mechanism can guide to improve synthetic methods to realize ligand?free shape-controlled perovskite NCs. 相似文献
18.
Yi‐Chin Chen Sheng‐Cih Huang Dr. Yu‐Kuo Wang Dr. Yuan‐Ting Liu Prof. Dr. Tung‐Kung Wu Prof. Dr. Teng‐Ming Chen 《化学:亚洲杂志》2013,8(11):2652-2659
In this study, surface‐functionalized, branched polyethylenimine (BPEI)‐modified YVO4:Bi3+,Eu3+ nanocrystals (NCs) were successfully synthesized by a simple, rapid, solvent‐free hydrothermal method. The BPEI‐coated YVO4:Bi3+,Eu3+ NCs with high crystallinity show broad‐band excitation in the λ=250 to 400 nm near‐ultraviolet (NUV) region and exhibit a sharp‐line emission band centered at λ=619 nm under excitation at λ=350 nm. The surface amino groups contributed by the capping agent, BPEI, not only improve the dispersibility and water/buffer stability of the BPEI‐coated YVO4:Bi3+,Eu3+ NCs, but also provide a capability for specifically targeted biomolecule conjugation. Folic acid (FA) and epidermal growth factor (EGF) were further attached to the BPEI‐coated YVO4:Bi3+,Eu3+ NCs and exhibited effective positioning of fluorescent NCs toward the targeted folate receptor overexpressed in HeLa cells or EGFR overexpressed in A431 cells with low cytotoxicity. These results demonstrate that the ligand‐functionalized, BPEI‐coated YVO4:Bi3+, Eu3+ NCs show great potential as a new‐generation biological luminescent bioprobe for bioimaging applications. Moreover, the unique luminescence properties of BPEI‐coated YVO4:Bi3+,Eu3+ NCs show potential to combine with a UVA photosensitizing drug to produce both detective and therapeutic effects for human skin cancer therapy. 相似文献
19.
《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(15):4316-4319
Two‐dimensional (2D) organic–inorganic hybrid perovskite nanosheets (NSs) are attracting increasing research interest due to their unique properties and promising applications. Here, for the first time, we report the facile synthesis of single‐ and few‐layer free‐standing phenylethylammonium lead halide perovskite NSs, that is, (PEA)2PbX4 (PEA=C8H9NH3, X=Cl, Br, I). Importantly, their lateral size can be tuned by changing solvents. Moreover, these ultrathin 2D perovskite NSs exhibit highly efficient and tunable photoluminescence, as well as superior stability. Our study provides a simple and general method for the controlled synthesis of 2D perovskite NSs, which may offer a new avenue for their fundamental studies and optoelectronic applications. 相似文献
20.
《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(28):8270-8274
The double perovskite family, A2MIMIIIX6, is a promising route to overcome the lead toxicity issue confronting the current photovoltaic (PV) standout, CH3NH3PbI3. Given the generally large indirect band gap within most known double perovskites, band‐gap engineering provides an important approach for targeting outstanding PV performance within this family. Using Cs2AgBiBr6 as host, band‐gap engineering through alloying of InIII/SbIII has been demonstrated in the current work. Cs2Ag(Bi1−x Mx )Br6 (M=In, Sb) accommodates up to 75 % InIII with increased band gap, and up to 37.5 % SbIII with reduced band gap; that is, enabling ca. 0.41 eV band gap modulation through introduction of the two metals, with smallest value of 1.86 eV for Cs2Ag(Bi0.625Sb0.375)Br6. Band structure calculations indicate that opposite band gap shift directions associated with Sb/In substitution arise from different atomic configurations for these atoms. Associated photoluminescence and environmental stability of the three‐metal systems are also assessed. 相似文献