Recent advances in atomic imaging of organic-inorganic hybrid perovskites

Three-dimensional organic-inorganic hybrid perovskites(OHPs)hold a great prospect for photovoltaic applications due to their outstanding electronic and optical properties.These fascinating properties of OHPs in combination with their scalable and low-cost production make OHPs promising candidates for next-generation optoelectronic devices.The ability to obtain atomistic insights into physicochemical properties of this class of materials is crucial for the future development of this field.Recent advances in various scanning probe microscopy techniques have demonstrated their extraordinary capability in real-space imaging and spectroscopic measurements of the structural and electronic properties of OHPs with atomic-precision.Moreover,these techniques can be combined with light illumination to probe the structural and optoelectronic properties of OHPs close to the real device operation conditions.The primary focus of this review is to summarize the recent progress in atomic-scale studies of OHPs towards a deep understanding of the phenomena discovered in OHPs and OHP-based optoelectronic devices.

Characterization of structural transitions and lattice dynamics of hybrid organic–inorganic perovskite CH3NH3PbI3

By combining temperature-dependent x-ray diffraction(XRD) with temperature-dependent Raman scattering, we have characterized the structural transitions and lattice dynamics of the hybrid organic–inorganic perovskite CH3NH3PbI3.The XRD measurements cover distinct phases between 15 K and 370 K and demonstrate a general positive thermal expansion.Clear anomalies are found around the transition temperatures.The temperature evolution of the lattice constants reveals that the transition at 160 K/330 K is of the first-/second-order type.Raman measurements uncover three strong lowfrequency modes, which can be ascribed to the vibration of the Pb/I atoms.The temperature evolution of the modes clearly catches these transitions at 160 K and 330 K, and confirms the transition types, which are exactly consistent with the XRD results.The present study may set an experimental basis to understand the high conversion efficiency in methylammonium lead iodide.

Aromatic bromination with hydrogen production on organic‐inorganic hybrid perovskite‐based photocatalysts under visible light irradiation

Aromatic bromides are important chemicals in nature and chemical industries.However,their tra‐ditional synthesis routes suffer from low atomic economy and pollutant formation.Herein,we show that organic-inorganic hybrid perovskite methylammonium lead bromide(MAPbBr_(3))nanocrystals stabilized in aqueous HBr solution can achieve simultaneous aromatic bromination and hydrogen evolution using HBr as the bromine source under visible light irradiation.By hybridizing MAPbBr_(3) with Pt/Ta_(2)O_(5) and poly(3,4‐ethylenedioxythiophene)polystyrene sulfonate as electron‐and hole‐transporting motifs,aromatic bromides were achieved from aromatic compounds with high yield(up to 99%)and selectivity(up to 99%)with the addition of N,N‐dimethylformamide or its analogs.The mechanistic studies revealed that the bromination proceeds via an electrophilic attack pathway and that HOBr may be the key intermediate in the bromination reaction.

Synthesis and Characterization of Layered Perovskite-type Organic-inorganic Hybrids(CnH2n+1NH3)2(CH3NH3)m-1PbmI3m+1(n=5-10,m=1,2)

Layered organic-inorganic hybrids（CnH2n＋1NH3）2（CH3NH3）m-1PbmI3m＋1 containing monolayer（m=1） and bilayer（m=2） perovsikte were synthesized by reactions in solution.The influences of the reactant ratio,solvent,reaction temperature,and reaction time on the structures of the products were investigated.The structures and the properties of the hybrids were characterized using X-ray diffraction（XRD）,scanning electron microscopy（SEM）,and ultraviolet and visible（UV） absorption spectroscopy.The XRD patterns and the SEM images demonstrate that the pure bilayer perovskite hybrids are obtained.The UV-vis spectra indicate that the number of the inorganic perovskite layer（m） has greater impact on the band gap than the number of the carbon atoms（n）.The band gap of bilayer hybrids（around 1.9 eV） is significantly less than that of monolayer hybrids（around 2.2 eV）.

Synthesis and Characterization of Layered Perovskite-type Organic-inorganic Hybrids (R-NH_3)_2(CH_3NH_3)Pb_2I_7

Layered organic-inorganic hybrids containing bilayer perovsikte （R-NH3）2（CH3NH3）Pb2I7 （where R=C12H25,C6H5C2H4） were synthesized by reactions in solution. The influences of the solvents and the reactant ratio on the structures of the products were investigated. The structures and the properties of the hybrids were characterized using X-ray diffraction （XRD） and ultraviolet and visible （UV） adsorption spectra. For comparing with the bilayer perovskite hybrids in structure and band gap magnitude, the hybrids containing monolayer perovskite （R-NH3）2PbI4 were also synthesized and characterized. The results demonstrate that the thickness of inorganic layer has obvious effect on the tunneling magnitude of the band gap but the organic part can be micro actuator of band gap.

New insight into the ultra-long lifetime of excitons in organic-inorganic perovskite： Reverse intersystem crossing

Recently, an effective exciton diffusion length L exceeding 100μm has been reported for organic- inorganic halide perovskites owing to both the high mobility and ultra-long lifetime of the excitons; however, the origin of ultra-long L is still unclear in nature. In some photoelectric materials, reverse intersystem crossing （RISC） from the triplet to the singlet state can enhance the quantum yield of pho- toluminescence greatly. In this study, our theoretical investigation indicated that the energy difference △E_st between the singlet state and the triplet state of CH_3NH_3Pbl_3 was less than 0.1 eV, which represents one crucial prerequisite for the occurrence of RISC. Meanwhile, the experimental results showed that the photoluminescence lifetime increased with the increasing temperature, a typical feature of RISC. Based on this study, we put forward the hypothesis that the ultra-long lifetime of excitons in organic-inorganic halide perovskite might be caused by the RISC process. This may provide a new insight into the important photophysical properties of such novel photovoltaic materials.

A New Bismuth(Ⅲ) Iodide Inorganic/organic Hybrid Solid Containing Large Heterocyclic Conjugated Organic Ligand: Synthesis, Properties and Calculations

A new bismuth（III） iodide inorganic/organic hybrid containing larger heterocyclic conjugated organic ligand, [（dppz）2Bi2I6]·2DMF （1） （dppz = dipyrido[3,2-a：2＇,3＇-c]phenazine）, has been synthesized by solution process and structurally determined by X-ray diffraction method. 1 crystallizes in triclinic, space group Pī with Mr= 1844.08, α = 9.215（5）, b = 11.488（6）, c = 12.424（9） ？, α = 106.66（2）, β = 90.84（2）, γ = 92.34（2）°, V = 1258.5（13） ？3, Z = 1, Dc = 2.433 g/cm3, F（000） = 830, μ（MoKα） = 10.702 mm–1, the final R = 0.0834 and wR = 0.1947 for 2749 observed reflections with I 〉 2σ（I）. 1 consists of a dimeric structure [（dppz）2Bi2I6], in which two [（dppz）BiI3] fragments are bridged by a pair of iodine atoms. Hydrogen bonds and π···π stacking interactions contribute to the structural extension and stabilization. Experimental band gap of about 2.13 eV indicates its semiconductor nature. The optical absorption spectrum and electronic structure were also discussed.

A New Inorganic-organic Hybrid Based on Biisoquinoline and Hexachloridostannate:Structure, Photoluminescence, Electrochemical Behavior and Theoretical Study

A new inorganic-organic hybrid constructed from biisoquinoline dication and tin halide, [（BIQBT）（Sn Cl6）]n（1, BIQBT = 1,4-bis（isoquinoline） butane）, has been synthesized and structurally determined by X-ray diffraction method. 1 crystallizes in the monoclinic system, space group Cc with Mr = 644.82, a = 16.589（3）, b = 18.388（4）, c = 8.5532（17）A, β = 108.75（3）°, V = 2470.6（9） A3, Z = 4, Dc = 1.736 g/cm^3, F（000） = 1281, μ（Mo Kα） = 1.697 mm^–1, the final R = 0.0197 and wR = 0.0493 for 4614 observed reflections with I 〉 2（I）. 1 consists of BIQBT^2＋dications and mononuclear hexachloridostannate Sn Cl62- anion, and hydrogen bonds among them contribute to the formation of a 1-D chain. Strong fluorescence can be detected in 1, which was explained by theoretical calculation. Its electrochemical behavior was investigated, and the theoretical calculations reveal that the π···π stacking interaction is dominated for their structural stabilization.

Recent progress on advanced transmission electron microscopy characterization for halide perovskite semiconductors

Halide perovskites are strategically important in the field of energy materials. Along with the rapid development of the materials and related devices, there is an urgent need to understand the structure–property relationship from nanoscale to atomic scale. Much effort has been made in the past few years to overcome the difficulty of imaging limited by electron dose,and to further extend the investigation towards operando conditions. This review is dedicated to recent studies of advanced transmission electron microscopy(TEM) characterizations for halide perovskites. The irradiation damage caused by the interaction of electron beams and perovskites under conventional imaging conditions are first summarized and discussed. Low-dose TEM is then discussed, including electron diffraction and emerging techniques for high-resolution TEM(HRTEM) imaging. Atomic-resolution imaging, defects identification and chemical mapping on halide perovskites are reviewed. Cryo-TEM for halide perovskites is discussed, since it can readily suppress irradiation damage and has been rapidly developed in the past few years. Finally, the applications of in-situ TEM in the degradation study of perovskites under environmental conditions such as heating,biasing, light illumination and humidity are reviewed. More applications of emerging TEM characterizations are foreseen in the coming future, unveiling the structural origin of halide perovskite’s unique properties and degradation mechanism under operando conditions, so to assist the design of a more efficient and robust energy material.

Transmission electron microscopy of organic-inorganic hybrid perovskites:myths and truths

Organic-inorganic hybrid perovskites(OIHPs)have attracted extensive research interest as a promising candidate for efficient and inexpensive solar cells.Transmission electron microscopy(TEM)characterizations that can benefit the fundamental understanding and the degradation mechanism are widely used for these materials.However,their sensitivity to the electron beam illumination and hence structural instabilities usually prevent us from obtaining the intrinsic information or even lead to significant artifacts.Here,we systematically investigate the structural degradation behaviors under different experimental factors to reveal the optimized conditions for TEM characterizations of OIHPs by using low-dose electron diffraction and imaging techniques.We find that a low temperature(-180°C)does not slow down the beam damage but instead induces a rapid amorphization for OIHPs.Moreover,a less severe damage is observed at a higher accelerating voltage.The beam-sensitivity is found to be facetdependent that a(100)exposed CH3NH3PbI3(MAPbI3)surface is more stable than a(001)surface.With these guidance,we successfully acquire the atomic structure of pristine MAPbI3 and identify the characterization window that is very narrow.These findings are helpful to guide future electron microscopy characterizations of these beam-sensitive materials,which are also useful for finding strategies to improve the stability and performance of the perovskite solar cells.

Flexible organic-inorganic hybrid perovskite solar cells

The area of organic-inorganic hybrid perovskite has undergone especially intense research and transformation over the past seven years. Although most of the focus is on achieving high power efficiencies(>20%) on rigid substrates by solution process, the flexible version has not been neglected and has also gone through vast improvements in terms of efficiencies and durability. In this review paper, the most recent three years' developments in flexible perovskite solar cells are covered, showcasing the key of strategies used to transform these cells from rigid to flexible. Future outlook will be presented at the end exhibiting the potential problems that need to be solved in order to send these novel flexible power generators into the future market.

钙钛矿材料:热电领域的潜力之星

硫系和卤化物钙钛矿材料具有优良的热电输运性能,以及易制备、稳定性良好等诸多优点,因而受到了广泛关注。筛选具有热电潜力的钙钛矿材料和提升现有钙钛矿材料的热电性能是目前研究的重点内容。本文回顾了钙钛矿和热电材料的基本理论,描述了材料热电性能的表征参数,综述了具有优良热电潜力的钙钛矿材料的研究进展,包括无机硫系和卤化物钙钛矿材料、有机复合钙钛矿材料以及氧化物钙钛矿材料等,并从电子结构、电输运性质、热输运性质以及热电性能调控方法等方面分析了钙钛矿材料具有优异热电优值和优良热电潜力的原因,展望了钙钛矿材料的热电应用前景。

有机-无机卤化物钙钛矿光伏材料MAPbI 3研究进展

有机无机杂化钙钛矿材料因具有合适的带隙,高光吸收系数,长载流子扩散长度和长寿命等优异的光电性能,在太阳能电池、光电探测器及柔性器件等领域展现出了广阔的应用前景。但有机无机杂化钙钛矿材料的毒性和稳定性问题仍然是其商业化进程中亟需解决的两个关键性问题。针对此问题,完全或部分替代有机无机杂化钙钛矿材料中的元素,已被证明是消除材料毒性,并调节其稳定性和光电性能的有效方法。本文全面综述了ABX_(3)型钙钛矿的A位、B位以及X位离子完全或部分替代对有机无机卤化物钙钛矿(MAPbI_(3))光电性能和稳定性的影响。分析了存在的问题及可能解决的方法,预测了其应用前景。

氧化锡电子传输层在正置钙钛矿太阳能电池中的研究进展

近年来,钙钛矿太阳能电池(Perovskite solar cells,PSCs)由于具有光伏性能优异、材料成本低、制造工艺简单等优势,引起了科研工作者广泛的研究兴趣。在PSCs中,电子传输层(Electron transport layer,ETL)在提取和传输光生电子方面起着至关重要的作用。氧化锡(SnO_(2))由于具有高光学透过率、高电子迁移率、良好的化学稳定性、合理的能级结构和可低温制备等优异性能,成为PSCs器件中理想的ETL。本文围绕SnO_(2) ETL在正置PSCs中的研究进展进行综述,首先介绍了SnO_(2)的结构与光电特性,并归纳了SnO_(2)的制备方法,随后对有机无机杂化PSCs及全无机PSCs中SnO_(2) ETL的改性进行了详细的阐述和总结,包括掺杂及界面修饰处理,最后总结全文,对SnO_(2) ETL的发展进行展望。

钙钛矿太阳能电池界面缺陷及其抑制方法

目前,绝大多数高效有机-无机卤化物钙钛矿(OIHP)太阳能电池都是由多晶钙钛矿薄膜构成,这些多晶薄膜表面或晶界往往含有大量的缺陷,将导致光生载流子发生非辐射复合,并诱导OIHP材料分解,从而使器件的光电转换效率(PCE)和稳定性降低。本综述分析了钙钛矿太阳能电池的缺陷类型及缺陷对钙钛矿太阳能电池(PSCs)性能的影响,详细介绍了通过钝化电极与传输层,或传输层与钙钛矿层间的界面缺陷以获得更高效率和高稳定性的钙钛矿太阳能电池方面的研究进展,展望了钝化分子的设计思路及钙钛矿光伏商业化应用所面临的挑战。

FA^(+)掺杂对无机钙钛矿CsPbBr_(3)发光性能的提升及其在白光发光二极管中的应用

钙钛矿半导体材料因其优异的光电转换特性、可调带隙、易于制备及低成本等优势,被广泛认为在新一代发光显示和光伏器件中具有巨大的应用潜力。CsPbBr_(3)等无机钙钛矿量子点凭借其独特的发光性质,已成为钙钛矿发光研究领域的焦点。然而,其发光性能和环境稳定性仍存在一定局限性。本文通过有机阳离子掺杂策略结合稳态和瞬态光谱学手段,系统研究了甲脒离子(FA^(+))掺杂对全无机钙钛矿CsPbBr_(3)光学性能和稳定性的优化。研究结果发现,FA+掺杂显著增强了CsPbBr_(3)发光性能,且在FA^(+)比例为20%时,其光致发光强度最强,较未掺杂前提高约2.8倍。结合变温荧光光谱分析,确定Cs_(0.8)FA_(0.2)PbBr_(3)的激子结合能为47.1 meV。FA^(+)的掺杂使得CsPbBr_(3)的纵向光学声子能降低,这有助于降低非辐射跃迁速率并提升发光量子产率。瞬态光谱分析表明,CsPbBr_(3)中掺杂FA+后,减缓了带内热激子弛豫和非辐射复合,从而使平均荧光寿命从13.68 ns增加至19.56 ns,激子寿命从774.1 ps延长至1319.2 ps。基于上述Cs_(0.8)FA_(0.2)PbBr_(3)量子点制备的发光二极管展现出发光稳定且理想的白光,其色度坐标为(0.3784,0.3163)。研究结果证实了掺杂甲脒离子来调控CsPbBr_(3)量子点光学性能的可行性,为白光发光二极管的设计和应用提供了指导。

刺激响应性有机-无机杂化溴氯化亚铜的制备

介绍了一个多刺激荧光响应有机-无机杂化溴氯化亚铜的制备、表征及性能测试的大学化学综合性实验。内容包括:有机-无机杂化溴氯化亚铜的制备,结构表征,以及对紫外(UV)光、水和热刺激发光性能的测试。本实验合成方法具有能耗低、操作简单快速、成本低的优点。学生通过本实验可以掌握溶液法的物理化学原理,提高基本实验技能,激发学生科学研究的兴趣,培养学生分析、解决实际工程问题和项目开发的能力。

钙钛矿太阳能电池的研究进展

钙钛矿太阳能电池由纳米晶致密层、钙钛矿型光活性层CH3NH3Pb X3(X=Cl、Br、I)、空穴传输层及对电极组成。其中光活性层吸光材料的种类及其成膜技术、空穴传输层材料类型及结构设计是影响钙钛矿太阳能电池光电性能的重要因素。本文结合钙钛矿太阳能电池近年来的最新研究进展,对影响器件光电性能的关键因素:光吸收层、空穴传输层、工艺参数以及结构设计等进行综述,同时展望了钙钛矿太阳能电池未来的发展趋势。

有机-无机杂化钙钛矿太阳电池的研究进展

可溶液加工的高效太阳电池及其活性层材料一直是全世界学术界与产业界关注与研究的热点。近年来,由于优异的光吸收特性和载流子传输能力,以及相对简单的制备方法,具有立体三维结构的有机-无机杂化钙钛矿晶体材料在太阳电池中的应用受到越来越多的关注,并在过去的两年内取得了重大的研究进展。有机-无机杂化钙钛矿太阳电池的光电转化效率(PCE)纪录被不断刷新,目前已达19.3%,与无机太阳电池相当。主要从有机-无机杂化钙钛矿材料的结构与性质、有机-无机杂化钙钛矿薄膜材料的制备方法、纳米多孔载体结构和平板结构钙钛矿太阳电池、杂化钙钛矿太阳电池的稳定性4个方面,介绍了有机-无机杂化钙钛矿太阳电池近期的研究进展,并对其发展方向进行了展望。

层状类钙钛矿结构有机-无机杂合物的结构设计思想

层状类钙钛矿结构有机-无机杂合物是由有机、无机组元在分子尺度上组装而成的一类新材料,其结构和能带具有可设计可控性,因此应用前景广阔。论述了无机类钙钛矿和类钙钛矿杂合物在结构上低维拆分与组装的设计思想。