Low-dimensional Perovskites Research Articles

One-dimensional corner-sharing perovskites: Syntheses, structural evolutions and tunable photoluminescence properties

In recent years, organic-inorganic hybrid lead halide perovskites have emerged as a highly promising class of light emitting diodes (LEDs) due to their diverse structures and promising properties. Herein, by choosing various organic molecules as cations, we successfully constructed a series of 1D perovskites of [PMDETA]PbBr5, [PMDETA]PbCl5, [DMPZ][MA]PbBr5, [EEDA][MA]PbCl5, [EPZ][MA]PbCl5 and [EPZ]3Pb2Br10. Under the different structural directing effects of organic cations, these 1D perovskites feature three different kinds of linear or zigzag 1D [PbX5]3− chains based on purely corner-shared octahedrons. As expected, these 1D perovskites exhibit tunable broadband light emissions from blue to yellow spectral range stemming from the self-trapped excitons based on systematical characterizations including time-resolved, temperature-dependent PL emissions and theoretical calculations. This work provides crystal structural engineering for low-dimensional perovskites and paves a new way to regulate the luminescent properties.

Phase-Pure Quasi-2D Perovskite by Protonation of Neutral Amine.

Phase control of low-dimensional metal-halide perovskites (LDPs) greatly affects their optoelectronic properties, and phase-pure LDPs are desirable to achieve efficient perovskite optoelectronic devices such as solar cells and light-emitting diodes. Herein, we introduce a method to obtain phase-pure LDP by using a neutral amine, cyclohexylmethyl amine (CHMA). The incorporation of CHMA into a formamidinium lead bromide (FAPbBr3) precursor solution leads to the protonation of the amine that allows the phase transition of 3D FAPbBr3 to phase-pure quasi-2D perovskite (n = 2). For comparison, cyclohexylmethylammonium bromide (CHMABr), which is a conventional form of ammonium halide salt with the same organic moiety to the amine, is used, which resulted in a 2D perovskite (n = 1). The perovskite films fabricated by the two different methodologies are characterized. This study paves the way for further research on the realization of phase-pure perovskites and their relevant optoelectronic devices.

Atomic resolution in situ observation on photon-induced reshaping and phase transitions of CsPbBr3 nanocube and quantum dot

Controlling the photon-induced reshaping and phase transitions of low-dimensional halide perovskites is a significant and challenging task. Using in situ Cs-corrected transmission electron microscopy with a nanosecond pulsed laser source, we traced CsPbBr3 nanocubes and quantum dots under different laser irradiation conditions, through a low-dose observation mode. We found that a high laser fluence with a short irradiation time (e.g., 300 mJ/cm2 in the range of seconds) triggers defect growth and a cubic-to-orthorhombic phase transition in perovskite nanocubes; however, a low laser fluence with a long irradiation time (e.g., 30 mJ/cm2 in the range of minutes) is actually like an annealing process that removes defects and gradually reshapes the perovskite samples into a round morphology, with the cubic phase well stabilized by the strong surface tension. Based on the in situ studies, we present a feasible and effective laser engineering approach for low-dimensional halide perovskite materials.

Tuning Spin-Polarized Lifetime in Two-Dimensional Metal-Halide Perovskite through Exciton Binding Energy.

Metal-halide perovskite semiconductors have attracted attention for opto-spintronic applications where the manipulation of charge and spin degrees of freedom have the potential to lower power consumption and achieve faster switching times for electronic devices. Lower-dimensional perovskites are of particular interest since the lower degree of symmetry of the metal-halide connected octahedra and the large spin-orbit coupling can potentially lift the spin degeneracy. To achieve their full application potential, long spin-polarized lifetimes and an understanding of spin-relaxation in these systems are needed. Here, we report an intriguing spin-selective excitation of excitons in a series of 2D lead iodide perovskite (n = 1) single crystals by using time- and polarization-resolved transient reflection spectroscopy. Exciton spin relaxation times as long as ∼26 ps at low excitation densities and at room temperature were achieved for a system with small binding energy, 2D EOA2PbI4 (EOA = ethanolamine). By tuning the excitation density and the exciton binding energy, we identify the dominant mechanism as the D'yakonov-Perel (DP) mechanism at low exciton densities and the Bir-Aronov-Pikus (BAP) mechanism at high excitation densities. Together, these results provide new design principles to achieve long spin lifetimes in metal-halide perovskite semiconductors.

Metal Halide Semiconductors beyond Lead-Based Perovskites for Promising Optoelectronic Applications.

In recent decades, metal halide semiconductors represented by lead-based halide perovskites have shown broad potential in optoelectronic applications. This family of semiconductors differs from traditional tetrahedral semiconductors in crystalline structure, chemical bonding, electronic-structure features, optoelectronic properties, as well as material fabrication method. At present, difficulties arising from both intrinsic material properties (including Pb toxicity and long-term stability) and technological aspects hinder their large-scale commercialization. In this Perspective, we focus on up-and-coming lead-free metal halide semiconductors toward high-performance optoelectronic applications. We start by outlining the advantages of metal halide semiconductors and their physical and chemical underpinnings. We then review composition and structure, electronic structure, optoelectronic properties, and device applications according to classification into three material categories, i.e., three-dimensional halide perovskites, low-dimensional perovskites and perovskite-like materials, and materials beyond perovskites. We conclude with an outlook on the challenges and opportunities of metal halide semiconductors and the future development of the field.

Performance analysis of highly efficient 2D/3D bilayer inverted perovskite solar cells

Photovoltaic conversion efficiency (PCE) acquired in perovskite solar cells (PSCs) is currently competitive with that of other commercial solar cells. Despite profound progress in PSCs in the last few years, achieving long term stability is considered as a prime hindrance for the commercialization of these solar cells. Recently, low dimensional perovskites have drawn extensive interests in research to improve photo-stability, however, wide bandgap limits output power of low dimensional perovskite-based solar cells. Two-dimensional/three-dimensional (2D/3D) bilayer PSCs can overcome this barrier via innovation in device engineering that can retain high performance and long-term photostability simultaneously. For example, inverted p-i-n structure of 2D/3D bilayer PSCs has drawn enormous interests in recent years due to cost-effectiveness, low temperature processing, and inhibited hysteresis characteristics. In this report, we present a numerical modeling approach to optimize the performance of an inverted 2D/3D bilayer PSC with a novel device architecture: ITO/NiOx/BA2MAn-1PbnI3n+1/MAPbI3/ZnO/Al. Perovskite materials with thickness of ∼900 nm (BA2MAn-1PbnI3n+1(200 nm)/MAPbI3 (700 nm)) and defect density of 2 × 1014 cm−3 yields best cell efficiency, that is up to ∼24.75%. Further optimization of electron transport layer and hole transport layer along with their donor and acceptor density level leads to 2.56% increase in the efficiency, that is from ∼23.53% to ∼24.75%. Our estimation suggests that incorporating 2D BA2MAn-1PbnI3n+1 perovskite into 3D MAPbI3 perovskite yield high throughput and simultaneously minimize the fabrication cost for active absorber layer in inverted PSCs.

Managing Growth and Dimensionality of Quasi 2D Perovskite Single-Crystalline Flakes for Tunable Excitons Orientation.

Hybrid perovskites are among the most promising materials for optoelectronic applications. Their 2D crystalline form is even more interesting since the alternating inorganic and organic layers naturally forge a multiple quantum-well structure, leading to the formation of stable excitonic resonances. Nevertheless, a controlled modulation of the quantum well width, which is defined by the number of inorganic layers (n) between two organic ones, is not trivial and represents the main synthetic challenge in the field. Here, a conceptually innovative approach to easily tune n in lead iodide perovskite single-crystalline flakes is presented. The judicious use of potassium iodide is found to modulate the supersaturation levels of the precursors solution without being part of the final products. This allows to obtain a fine tuning of the n value. The excellent optical quality of the as synthesized flakes guarantees an in-depth analysis by Fourier-space microscopy, revealing that the excitons orientation can be manipulated by modifying the number of inorganic layers. Excitonic out-of-plane component, indeed, is enhanced when "n" is increased. The combined advances in the synthesis and optical characterization fill in the picture of the exciton behavior in low-dimensional perovskite, paving the way to the design of materials with improved optoelectronic characteristics.

Pressure-induced emission from low-dimensional perovskites

Pressure-induced emission from low-dimensional perovskites

Intrinsic white-light emission from low-dimensional perovskites for white-light-emitting diodes with high-color-rendering index

High-performance white-light-emitting diodes (WLEDs) are regarded as a promising next-generation solid-state light source. However, a low-color-rendering index (CRI), consumption of rare-earth elements, and inevitable self-absorption remain the major challenges for high-performance WLEDs. Here, lead-doped Cs3Cu2Br5 nanocrystals (NCs) with a zero-dimensional structure are prepared to facilitate stable and intrinsic white-light emission (IWE) without phosphors and other compositions. The lead dopants are expected to be centers of isolated [PbBr6] octahedrons, in which self-trapped excitons originating from distorted octahedra can form. Subsequently, a broadband blue photoluminescence (PL) from the Cs3Cu2Br5 and a broadband red PL from the lead doping are observed, exhibiting intrinsic white-light emission overall. The doped Cs3Cu2Br5 NCs are then employed to fabricate WLEDs, which possess a high CRI of 98 and an excellent 200-h operating stability.

The Impact of Solvent Vapor on the Film Morphology and Crystallization Kinetics of Lead Halide Perovskites during Annealing.

One of the key factors for the remarkable improvements of halide perovskite solar cells over the last few years is the increased control over perovskite crystallinity and its thin film morphology. Among various processing methods, solvent vapor-assisted annealing (SVAA) has proven to be promising in achieving high-quality perovskite films. However, a comprehensive understanding of the perovskite crystallization process during SVAA is still lacking. In this work, we use a home-built setup to precisely control the SVAA conditions to investigate in detail the perovskite crystallization kinetics. By changing the solvent vapor concentration during annealing, the perovskite grain size can be tuned from 200 nm to several micrometers. We monitor the crystallization kinetics during solvent-free annealing and SVAA using in situ grazing incidence wide-angle X-ray scattering, where we find a diminished perovskite growth rate and the formation of low dimensional perovskite at the top of the perovskite layer during SVAA. Scanning electron microscopy images of the final films further suggest that the perovskite growth follows an Ostwald ripening process at higher solvent concentrations. Thus, our results will contribute to achieve a more targeted processing of perovskite films.

Abnormal Phase Transition and Band Renormalization of Guanidinium-Based Organic-Inorganic Hybrid Perovskite.

Low-dimensional organic-inorganic hybrid perovskites have attracted much interest owing to their superior solar conversion performance, environmental stability, and excitonic properties compared to their three-dimensional (3D) counterparts. Among reduced-dimensional perovskites, guanidinium-based perovskites crystallize in layered one-dimensional (1D) and two-dimensional (2D). Here, our studies demonstrate how the dimensionality of the hybrid perovskite influences the chemical and physical properties under different pressures (i.e., bond distance, angle, vdW distance). Comprehensive studies show that 1D GuaPbI3 does not undergo a phase transition even up to high pressures (∼13 GPa) and its band gap monotonically reduces with pressure. In contrast, 2D Gua2PbI4 exhibits an early phase transition at 5.5 GPa and its band gap follow nonmonotonic pressure response associated with phase transition as well as other bond angle changes. Computational simulations reveal that the phase transition is related to the structural deformation and rotation of PbI6 octahedra in 2D Gua2PbI4 owing to a larger degree of freedom of deformation. The soft lattice allows them to uptake large pressures, which renders structural phase transitions possible. Overall the results offer the first insights into how layered perovskites with different dimensionality respond to structural changes driven by pressure.

Molecular engineering towards efficientwhite-light-emitting perovskite

Low-dimensional hybrid perovskites have demonstrated excellent performance as white-light emitters. The broadband white emission originates from self-trapped excitons (STEs). Since the mechanism of STEs formation in perovskites is still not clear, preparing new low-dimensional white perovskites relies mostly on screening lots of intercalated organic molecules rather than rational design. Here, we report an atom-substituting strategy to trigger STEs formation in layered perovskites. Halogen-substituted phenyl molecules are applied to synthesize perovskite crystals. The halogen-substituents will withdraw electrons from the branched chain (-R-NH3+) of the phenyl molecule. This will result in positive charge accumulation on -R-NH3+, and thus stronger Coulomb force of bond (-R-NH3+)-(PbBr42−), which facilitates excitons self-trapping. Our designed white perovskites exhibit photoluminescence quantum yield of 32%, color-rendering index of near 90 and chromaticity coordinates close to standard white-light. Our joint experiment-theory study provides insights into the STEs formation in perovskites and will benefit tailoring white perovskites with boosting performance.

Naphthalenediimide/Formamidinium-Based Low-Dimensional Perovskites

Low-dimensional hybrid perovskites have emerged as promising materials for optoelectronic applications. Although these materials have already demonstrated enhanced stability as compared to their three-dimensional perovskite analogues, their functionality has been limited by the insulating character of the organic moieties that primarily play a structure-directing role. This is particularly the case for the layered (2D) perovskite materials based on formamidinium lead iodide (FAPbI3) that remain scarce. We demonstrate a low-dimensional hybrid perovskite material based on a SPbI4 composition incorporating an electroactive naphthalenediimide (NDI) moiety as an organic spacer (S) between the perovskite slabs and evidence the propensity of the spacer to stabilize the α-FAPbI3 perovskite phase in hybrid low-dimensional SFAn–1PbnI3n+1 perovskite compositions. This has been investigated by means of solid-state nuclear magnetic resonance spectroscopy in conjunction with molecular dynamics simulations and density functional theory calculations. Theoretical calculations suggest an electronic contribution of the organic spacer to the resulting optoelectronic properties, which was confirmed by transient absorption spectroscopy. We have further analyzed these materials by time-resolved microwave conductivity measurements, revealing challenges for their application in photovoltaics.

Passivation Strategies through Surface Reconstruction toward Highly Efficient and Stable Perovskite Solar Cells on n-i-p Architecture

Perovskite solar cells have achieved remarkable enhancement in their performance in recent years. However, to get an entrance to the photovoltaic market, great effort is still necessary to further improve their efficiency as well as their long-term stability under various conditions. Among various types of approaches (including compositional engineering, dopant engineering, self-assembled monolayers (SAMs), et al.), interfacial engineering through passivation treatment has been considered as one of the most effective strategies to reduce the non-radiative recombination within the PSCs. Thus, this short review summaries recent efforts on chemical interfacial passivation strategies from a different perspective owing to their common phenomena of reconstructing the perovskite surface via the formation of three-dimensional perovskite, low-dimensional perovskite and synergistic effect provided by a mixed-salt passivation system, respectively.

Predictive Design Model for Low-Dimensional Organic-Inorganic Halide Perovskites Assisted by Machine Learning.

Low-dimensional organic-inorganic halide perovskites have attracted interest for their properties in exciton dynamics, broad-band emission, magnetic spin selectivity. However, there is no quantitative model for predicting the structure-directing effect of organic cations on the dimensionality of these low-dimensional perovskites. Here, we report a machine learning (ML)-assisted approach to predict the dimensionality of lead iodide-based perovskites. A literature review reveals 86 reported amines that are classified into "2D"-forming and "non-2D"-forming based on the dimensionality of their perovskites. Machining learning models were trained and tested based on the classification and descriptor features of these ammonium cations. Four structural features, including steric effect index, eccentricity, largest ring size, and hydrogen-bond donor, have been identified as the key controlling factors. On the basis of these features, a quantified equation is created to calculate the probability of forming 2D perovskite for a selected amine. To further illustrate its predicting capability, the built model is applied to several untested amines, and the predicted dimensionality is verified by growing single crystals of perovskites from these amines. This work represents a step toward predicting the crystal structures of low dimensional hybrid halide perovskites using ML as a tool.

Perovskitoid‐Templated Formation of a 1D@3D Perovskite Structure toward Highly Efficient and Stable Perovskite Solar Cells

AbstractLongevity is a long‐standing concern for organic–inorganic hybrid perovskite solar cells (PSCs). Recently, the use of low dimensional perovskite has been proven to be a promising strategy to improve the stability of PSCs. Herein, it is demonstrated that 1D perovskitoid based on 2‐diethylaminoethylchloride cations can act as a template to induce 1D@3D perovskite structure, leading to smoother surface texture, longer charge‐carrier lifetime, smaller residual tensile strain, and reduced surface‐defect density in the perovskite film. With this strategy, highly efficient and stable 1D@3D PSC with excellent reproducibility, showing a champion power conversion efficiency (PCE) of 22.9% under standard AM 1.5 G one sun illumination is realized. The unencapsulated optimized devices can retain 94.7%, 92.4%, and 90.0% of their initial PCEs for 2100, 2200, and 2200 h under ambient air, 85 °C and illumination conditions, respectively.

Efficient and Stable Blue Perovskite Light-Emitting Devices Based on Inorganic Cs4PbBr6 Spaced Low-Dimensional CsPbBr3 through Synergistic Control of Amino Alcohols and Polymer Additives.

Perovskite light-emitting devices (PeLEDs) have drawn a great deal of attention because of their exceptional optical and electrical properties. However, as for the blue PeLEDs based on low-dimensional (LD) CsPbBr3, the low conductivity of the widely used organic spacers as well as the difficulty of forming pure and uniform LD CsPbBr3 phase have severely inhibited the device performance such as stability and efficiency. In this work, we report an effective strategy to obtain high-quality LD CsPbBr3 by using a novel spacer of inorganic Cs4PbBr6 instead of the common long-chain ammonium halides. We found that a 3-amino-1-propanol (3AP)-modified PEDOT:PSS was helpful to stimulate the formation of the LD blue emissive CsPbBr3:Cs4PbBr6 composite. We also revealed that an additive of poly(vinylpyrrolidone) (PVP) in the precursor can limit further growth of LD perovskite phase into 3D perovskite phase upon annealing, thus resulting in a uniformly distributed LD perovskite with high color stability. Consequently, efficient blue PeLEDs @ 485 nm with a brightness of 2192 cd/m2, current efficiency of 2.68 cd/A, and external quantum efficiency of 2.3% was successfully achieved. More importantly, the device showed much improved working stability compared to those with the spacer of organic ammonium halides. Our results provide some helpful insights into developing efficient and stable blue PeLEDs.

Zhijun Ning

Angewandte ChemieVolume 133, Issue 31 p. 16887-16887 Introducing …Free Access Zhijun Ning First published: 01 July 2021 https://doi.org/10.1002/ange.202107321AboutSectionsPDF ToolsRequest permissionAdd to favorites ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat Abstract “My favorite thing about my lab group is interdisciplinary research atmosphere. … My biggest inspiration is walking along the grand gallery in ShanghaiTech campus …” Find out more about Zhijun Ning in his Introducing … Profile. Zhijun Ning The author presented on this page has published his first article as a submitting corresponding author in Angewandte Chemie: “Low-Dimensional Inorganic Tin Perovskite Solar Cells Prepared by Templated Growth”: H. Li, X. Jiang, Q. Wei, Z. Zang, M. Ma, F. Wang, W. Zhou, Z. Ning, Angew. Chem. Int. Ed. 2021, 60, doi.org/10.1002/anie.202104958; Angew. Chem. 2021, 133, doi.org/10.1002/ange.202104958. Position: Associate Professor (Tenured), School of Physical Science and Technology, ShanghaiTech University Homepage: https://spst.shanghaitech.edu.cn/2018/0301/c2349a52605/page.htm ORCID: orcid.org/0000-0002-9130-3490 Education: 2000–2004 Undergraduate studies, Liaoning Shihua University (China) 2009 PhD with He Tian, East China University of Science and Technology 2009–2011 Postdoc with Hans Ågren and Ying Fu, Royal Institute of Technology (Sweden) 2011–2014 Postdoc with Edward H. Sargent, University of Toronto (Canada) Research: Solution-processed optoelectronic materials and devices, especially tin perovskite solar cells and quantum dot infrared photodetectors Hobbies: Basketball, music The greatest scientific advance of the next decade will be a performance leap of clean energy materials and system. Science is fun because there are lots of surprise. The most exciting thing about my research is the development of low-dimensional tin perovskite solar cells. I chose my current career path because of strong curiosity for an unknown world. I advise my students to stay curious and be persistent. A turning point in my career was joining ShanghaiTech University. My long-term goal is real applications of solution-processed optoelectronic materials and devices. My group has fun by having parties. My not-so-secret passion is to develop new materials and devices. I lose track of time when traveling. A good day at work starts with a cup of tea. My biggest inspiration is walking along the grand gallery in the campus. If I had one year of paid leave I would read and travel. The most important quality of a mentor is self-discipline. My favorite thing about my lab group is interdisciplinary research atmosphere. My favorite structure type is the cubic. My favorite place on earth is my hometown, a village at Hunan, central part of China. My favorite food is a home-made dried bean curd in my hometown. My favorite drink is green tea. My favorite music is rock. Behind the Science References 1The tin perovskite solar cell is emerging as an important thin-film photovoltaic technology. The improvement of its stability is an urgent task nowadays for which the combination of low-dimensional and inorganic scaffold structures is a promising approach. However, films based on low-dimensional inorganic tin perovskite structure usually show high defect density and inhomogeneous orientation. We spent a lot of time to address this problem without success. Accidentally, my student Hansheng discovered that a special reagent can help to grow a high-quality film. We then revealed the intermediate structure and clarified the kinetics of crystal growth. Google Scholar Volume133, Issue31July 26, 2021Pages 16887-16887 This is the German version of Angewandte Chemie. Note for articles published since 1962: Do not cite this version alone. Take me to the International Edition version with citable page numbers, DOI, and citation export. We apologize for the inconvenience. ReferencesRelatedInformation

Directing the Self-Assembly of Conjugated Organic Ammonium Cations in Low-Dimensional Perovskites by Halide Substitution

At present, two-dimensional (2D) hybrid organic–inorganic perovskites (HOIPs) are drawing significant interest because of their potential use in different optoelectronic applications, that is, photovoltaics and photodetectors. Here, we report on a series of 2D layered HOIPs (Bit-C3)2PbX4 (with X = Cl, Br, and I) containing a 2,2′-bithiophene chromophore functionalized with a propylammonium tethering chain as a model molecule. The optical properties, crystal structure, and phase behavior of the 2D layered HOIPs are studied in depth. The crystal structures with the chemical formula (Bit-C3)2PbX4 (with X = Cl, and Br) are successfully obtained. Contrastingly, different crystal structures with an inorganic framework containing face- and corner-sharing octahedra were identified for the iodide-based HOIP. The phase diversity and thermal stability of the (Bit-C3)2PbX4 (with X = Cl, Br, and I) thin films were investigated via in situ measurements. Here, the presence of lower-dimensional hybrids with reduced electronic dimensionality within the iodide-based thin film is demonstrated. Additionally, we show that the 2D hybrid thermal stability is dependent on the type of lead(II)halide framework employed. We suggest that, via halide substitution from iodide to bromide and chloride, the molecular degrees of freedom of the Bit-C3 ammonium cations are reduced by spatial confinement of a smaller inorganic framework, therefore, limiting the formation of lower-dimensional hybrids besides the targeted 2D layered HOIP. This study illustrates the importance of efficiently utilizing the space supplied by the inorganic framework in which the organic ammonium cations can reside within a 2D layered HOIP. This, in turn, dictates how the organic ammonium cations arrange themselves within the organic layer and influences the adopted crystal structure of the hybrid.

Linear Relationship between the Dielectric Constant and Band Gap in Low-Dimensional Mixed-Halide Perovskites

Linear Relationship between the Dielectric Constant and Band Gap in Low-Dimensional Mixed-Halide Perovskites