Advances in the Application of Perovskite Materials

Nowadays, the soar of photovoltaic performance of perovskite solar cells has set off a fever in the study of metal halide perovskite materials. The excellent optoelectronic properties and defect tolerance feature allow metal halide perovskite to be employed in a wide variety of applications. This article provides a holistic review over the current progress and future prospects of metal halide perovskite materials in representative promising applications, including traditional optoelectronic devices(solar cells, light-emitting diodes, photodetectors, lasers), and cutting-edge technologies in terms of neuromorphic devices(artificial synapses and memristors) and pressure-induced emission. This review highlights the fundamentals, the current progress and the remaining challenges for each application, aiming to provide a comprehensive overview of the development status and a navigation of future research for metal halide perovskite materials and devices.

CoS_(2)nanowires supported graphdiyne for highly efficient hydrogen evolution reaction

Transition metal sulfides are an important category for hydrogen evolution reaction(HER).However,only few edge unsaturated sulfurs functionalize as catalytic sites,which has dramatically limited the catalytic activity and stability.In this work,planar unsaturated sulfurs in(211)plane of the CoS_(2)nanowires have been successfully activated through constructing Graphdiyne-CoS_(2)heterojunction nanocomposites.The corresponding electrons transfer energy barriers for these planar unsaturated sulfurs have been significantly diminished,which are induced by the synergetic effects of the sp~1 hybridized carbons and unsaturated planar sulfurs.In addition,DFT simulations reveal the synergetic effects of the sp~1 hybridized carbons and unsaturated planar sulfurs can promote electron transfer kinetics of the key step,VolmerHeyrovsky step,of the reaction.As expected,the Graphdiyne-CoS_(2)heterojunction nanocomposites exhibit superior HER catalytic performance with low overpotential of 97 mV at 10 mA cm^(-2),and the Tafel slope of 56 mV dec^(-1).Furthermore,the heterojunction shows outstanding stability as well due to the pr tection of the Graphdiyne(GDY).The approach thus paves the way for the further efficient transition metal disulfides catalyst manufactures.

Methylammonium-and bromide-free perovskites enable efficient and stable photovoltaics

Hybrid perovskite solar cell(PSC)has attracted extensive research interest due to its rapid increase in efficiency,regarding as one of the most promising candidates for the next-generation photovoltaic technology.The certified power conversion efficiency of the devices based on formamidinium lead iodide(FAPbI_(3))perovskite has reached 25.5%,approaching the record of monocrystalline silicon solar cells.Unfortunately,the blackα-phase FAPbI_(3)materials can spontaneously transform to non-optically activeδ-phase at room temperature,which greatly hinder their photovoltaic application.In order to overcome this problem,various strategies,especially introducing methylammonium(MA^(+)),caesium(Cs^(+))and bromide(Br^(-))ions into the materials,have been widely adopted.However,MA^(+)can largely reduce the thermal stability of the materials.Furthermore,the introduction of Br^(-)can enlarge the materials'bandgap,resulting in a reduced theoretical efficiency.Keeping these in mind,developing the strategies which without using MA^(+)and Br^(-)is the inevitable trend.Here,we focus on the recent progresses of stabilizingαFAPbI_(3)without employing MA^(+)and Br^(-),and discuss the advantages of inorganic ions doping and dimensionality engineering to stabilizedαFAPbI_(3).Meanwhile,in order to deeply understand the relationship between the semiconducting properties and device performance of the corresponding materials,we then summarize several significant strategies to suppress the non-radiation recombination,such as interface modification and trap passivation.Finally,we propose to develop more effective'A-site'alternatives to stabilizeαFAPbI_(3),which is expected to achieve high-efficient PSCs with long-term stability,facilitating its commercialization process.

Tuning exciton dynamics by the dielectric confinement effect in quasi-two-dimensional perovskites

The dielectric confinement effect plays an essential role in optoelectronic devices.Existing studies on the relationship between the dielectric confinement and the photoelectric properties are inadequate.Herein,three organic spacers with different dielectric constants are employed to tune the exciton dynamics of quasi-two-dimensional(quasi-2D)Ruddlesden–Popper perovskite films.Femtosecond transient absorption spectroscopy reveals that the small dielectric constant ligand enables a weak dynamic disorder and a large modulation depth of the coherent phonons,resulting in a more complete energy transfer and the inhibition of a trap-mediated nonradiative recombination.Additionally,the increase in the bulk-ligand dielectric constant reduces the corresponding exciton binding energy and then suppresses the Auger recombination,which is beneficial for high-luminance lightemitting diodes.This work emphasizes the importance of dielectric confinement for regulating the exciton dynamics of layered perovskites.

A universal hydrochloric acid-assistant powder-to-powder strategy for quick and mass preparation of lead-free perovskite microcrystals

Lead-free halide perovskite materials possess low toxicity,broadband luminescence and robust stability compared with conventional lead-based perovskites,thus holding great promise for eyes-friendly white light LEDs.However,the traditionally used preparation methods with a long period and limited product yield have curtailed the commercialization of these materials.Here we introduce a universal hydrochloric acid-assistant powder-to-powder strategy which can accomplish the goals of thermal-,pressure-free,eco-friendliness,short time,low cost and high product yield,simultaneously.The obtained Cs_(2)Na_(0.9)Ag_(0.1)In_(0.95)Bi_(0.05)Cl_(6)microcrystals exhibit bright self-trapped excitons emission with quantum yield of(98.3±3.8)%,which could retain(90.5±1.3)%and(96.8±0.8)%after continuous heating or ultraviolet-irradiation for 1000 h,respectively.The phosphor converted-LED exhibited near-unity conversion efficiency from ultraviolet chip to self-trapped excitons emission at~200 mA.Various ions doping(such as Cs_(2)Na_(0.9)Ag_(0.1)InCl_(6):Ln^(3+))and other derived lead-free perovskite materials(such as Cs_(2)ZrCl_(6)and Cs_(4)MnBi_(2)Cl_(12))with high luminous performance are all realized by our proposed strategy,which has shown excellent availability towards commercialization.

高稳定性铋基钙钛矿纳米晶的可控合成:结构和光物理性质

铋基钙钛矿因毒性低成为铅基钙钛矿的潜在替代品.目前,对铋基钙钛矿纳米晶的化学组成、晶体结构以及光物理过程的研究还缺乏系统性.特别地,紫外-可见吸收光谱和激发态载流子动力学,在已发表的论文中存在相当大的争议.在本文中,我们通过热注入法成功地合成了纯相的Cs_(3)BiBr_(6)和Cs_(3)Bi_(2)Br_(9)纳米晶,并通过调节热注入的温度来精确控制二者的化学组成和结构.在此基础上,系统研究了不同形貌和不同尺寸的Cs_(3)Bi_(2)Br_(9)纳米晶的紫外-可见吸收光谱,澄清了在这方面存在的争议.采用飞秒瞬态吸收光谱系统研究了Cs_(3)Bi_(2)Br_(9)纳米晶的激发态载流子动力学,结果表明载流子在被激发后的3 ps内会发生一个自捕获过程.与配体辅助再沉积法相比,用热注入法制备的Cs_(3)Bi_(2)Br_(9)纳米晶具有更好的光稳定性.基于Cs_(3)Bi_(2)Br_(9)纳米晶的光电探测器具有灵敏的光响应,显示出其在光电探测方面的应用潜力.

Tuning coherent phonon dynamics in two-dimensional phenylethylammonium lead bromide perovskites

Organic-inorganic layered perovskites are two-dimensional quantum well layers in which the layers of lead halide octahedra are stacked between the organic cation layers.The packing geometry of the soft organic molecules and the stiff ionic crystals induce structural deformation of the inorganic octahedra,generating complex lattice dynamics.Especially,the dielectric confinement and ionic sublattice lead to strong coupling between the photogenerated excitons and the phonons from the polar lattice which intensively affects the properties for device applications.The anharmonicity and dynamic disorder from the organic cations participate in the relaxation dynamics coupled with excitations.However,a detailed understanding of this underlying mechanism remains obscure.This work investigates the electron–optical phonon coupling dynamics by employing ultrafast pump-probe transient absorption spectroscopy.The activated different optical phonon modes are observed via systematic studies of(PEA)_(2)PbBr_(4) perovskite films on the ultrafast lattice vibrational dynamics.The experimental results indicate that solvent engineering has a significant influence on lattice vibrational modes and coherent phonon dynamics.This work provides fresh insights into electron-optical phonon coupling for emergent optoelectronics development based on layered perovskites.

Frontiers in circularly polarized luminescence:molecular design,self-assembly,nanomaterials,and applications

The research in circularly polarized luminescence has attracted wide interest in recent years.Efforts on one side are directed toward the development of chiral materials with both high luminescence efficiency and dissymmetry factors,and on the other side,are focused on the exploitations of these materials in optoelectronic applications.This review summarizes the recent frontiers(mostly within five years)in the research in circularly polarized luminescence,including the development of chiral emissive materials based on organic small molecules,compounds with aggregation-induced emissions,supramolecular assemblies,liquid crystals and liquids,polymers,metal-ligand coordination complexes and assemblies,metal clusters,inorganic nanomaterials,and photon upconversion systems.In addition,recent applications of related materials in organic light-emitting devices,circularly polarized light detectors,and organic lasers and displays are also discussed.

High-performance quasi-2D perovskite light-emitting diodes: from materials to devices

Quasi-two-dimensional(quasi-2D)perovskites have attracted extraordinary attention due to their superior semiconducting properties and have emerged as one of the most promising materials for next-generation lightemitting diodes(LEDs).The outstanding optical properties originate from their structural characteristics.In particular,the inherent quantum-well structure endows them with a large exciton binding energy due to the strong dielectricand quantum-confinement effects;the corresponding energy transfer among different n-value species thus results in high photoluminescence quantum yields(PLQYs),particularly at low excitation intensities.The review herein presents an overview of the inherent properties of quasi-2D perovskite materials,the corresponding energy transfer and spectral tunability methodologies for thin films,as well as their application in high-performance LEDs.We then summarize the challenges and potential research directions towards developing high-performance and stable quasi-2D PeLEDs.The review thus provides a systematic and timely summary for the community to deepen the understanding of quasi-2D perovskite materials and resulting LED devices.

低维钙钛矿产生强电致发光

Light-emitting diodes(LEDs)are changing the energy and lighting industry due to their high power efficiencies,low energy consumption,and long operational lifetimes.While epitaxiallygrown LEDs are the current industry standard,their incompatibility with large-area displays and flexible substrates precludes their use in many applications.Solution-processed light-emitting materials are more versatile and can be easily coated onto a variety of substrates using modern deposition techniques such as vapor deposition,spin-coating,dip-coating,and spray-painting.With these advantages,organic light-emitting diodes(OLEDs)have been widely applied to TVs,cell phones,and semi-transparent displays.They,however,suffer from resolution-transparency trade-off and incompatibility with high-temperature processes.Quantum dot(QD)light-emitting diodes(QLEDs)have sharper emission features and higher stabilities.However,QD emitting layers also have low mobilities,and thus the devices require large voltages for operation due to the presence of surface organic ligands.

Two-dimensional perovskite capping layer for stable and efficient tin-lead perovskite solar cells

Mixed tin-lead iodide perovskites exhibit the characteristics of low toxicity and improved light harvesting ability up to nearinfrared(NIR) spectral region, making them as an attractive alternative for traditional lead based perovskites. However, the performance of lead-based perovskites solar cells is still far inferior to their lead analogues owing to the unavoidable oxidation of Sn^(2+)to Sn^(4+). Here we introduced two-dimensional(2D) perovskite on the top of three dimensional(3D) perovskite film as a capping layer to reduce the self-oxidation, and thus improved the device stability. 2D capping layer was then confirmed by X-ray diffraction(XRD) and X-ray photoelectron spectroscopy(XPS) analysis. The existence of the 2D protecting thin layer significantly reduce the spontaneous Sn^(2+)oxidation, thus improve the device performance and reduce the hysteresis. The phenomena could be ascribed to the improved charge extraction efficiency causing by prohibited nonradiative recombination. On top of this, the photovoltaic devices based on conventional-structure configuration were fabricated. Taking advantage of the 2D capping layer, 2D/3D hybrid perovskite photovoltaic devices achieve a open-circuit voltage(Voc) of 0.77 V with short circuit current density(Jsc) of 26.60 mA cm^(-2), delivering the best-performing power conversion efficiency of 15.5%. Moreover, the 2D/3D perovskite devices maintained 60% its initial efficiency after 40 h exposed in air(humidity around 30%, temperature 22 °C),while 3D perovskite-based devices completely failed.

Lanthanide doped lead-free double perovskites as the promising next generation ultra-broadband light sources

Efficient ultra-broadband emitter is realized by using lanthanide ion doping coupled with“DPs-in-glass composite”(DiG)structure.The synergy of self-trapped exciton together with the energy transition induce this ultra-broadband emission emerge.

Employ ionic liquid to stabilize black-phase formamidinium perovskites

The certified power conversion efficiency(PCE)of per-ovskite solar cells which have emerged as the most promising candidates for next-generation thin-film photovoltaics has exceeded 25%.Among all available compositions,formamidinium lead iodide perovskite(FAPbI_(3))has a theoretically higher efficiency than the other perovskite analogues due to its narrower bandgap[1,2]and hence has attracted widespread attention.