The application of perovskite materials in solar water splitting

Solar water splitting is a promising strategy for sustainable production of renewable hydrogen,and solving the crisis of energy and environment in the world.However,large-scale application of this method is hampered by the efficiency and the expense of the solar water splitting systems.Searching for non-toxic,low-cost,efficient and stable photocatalysts is an important way for solar water splitting.Due to the simplicity of structure and the flexibility of composition,perovskite based photocatalysts have recently attracted widespread attention for application in solar water splitting.In this review,the recent developments of perovskite based photocatalysts for water splitting are summarized.An introduction including the structures and properties of perovskite materials,and the fundamentals of solar water splitting is first provided.Then,it specifically focuses on the strategies for designing and modulating perovskite materials to improve their photocatalytic performance for solar water splitting.The current challenges and perspectives of perovskite materials in solar water splitting are also reviewed.The aim of this review is to summarize recent findings and developments of perovskite based photocatalysts and provide some useful guidance for the future research on the design and development of highly efficient perovskite based photocatalysts and the relevant systems for water splitting.

Organolead trihalide perovskite materials for efficient light emitting diodes

Organolead trihalide perovskite materials have been attracting increasing attention due to their promising role in solid solar cells. Several advantages make them potential candidates for optoelectronics:(1) solution- or/and vapor-processed preparation at low temperature;(2) tunable optical bandgap, wide absorption spectrum but narrow photoluminescence peaks;(3) long car-rier life time, large diffusion length and high charge mobility;(4) various nanostructures via tuning capping agents and sol-vents. In this review, we summarize recent attempts toward efficient LEDs based on organolead trihalide perovskite materials. The strategies of materials science, device design and interface engineering are highlighted. Recent development and future perspectives are summarized for practical perovskite light technologies.

Rapid development in two-dimensional layered perovskite materials and their application in solar cells

Two-dimensional （2D） layered organic-inorganic hybrid perovskite （2D PVK） materials have beenrecently developed as a novel candidate for photovoltaic application with high stability and a maximumpower conversion efficiency of 12.5%. This article summarized these newly emerging 2D PVK materialsand their uses in solar cells. The structural, physical, and chemical properties as well as the classificationof 2D PVK materials are discussed. The photovoltaic performance parameters of various 2D perovsldtesolar cells （2D PSCs） are summarized and their device stability is compared with conventional 3Dperovskite solar cells （3D PSCs）. It has been concluded that 2D PVKs show greater stability upon humidity,heat stress, and light intensity as compared to 3D analogues and act as a class of promising materials forapplication in solar cells.

Recent theoretical progress in the development of perovskite photovoltaic materials

Since the seminal work by Kojima et al. in 2009, solar cells based on hybrid organic-inorganic perovskites have attracted considerable attention and experienced an exponential growth, with photovoltaic efficiencies as of today reaching above 22%. Despite such an impressive development, some key scientific issues of these materials, including the presence of toxic lead, the poor long-term device stability under heat and humidity conditions, and the anomalous hysteresis of the current-voltage curves shown by various solar cell devices, still remain unsolved and constitute an important focus of experimental and theoretical researchers throughout the world. Density functional theory calculations have been successfully applied to exploring structural and electronic properties of semiconductors, complementing the experimental results in search and discovery of novel functional materials. In this review, we summarize the current progress in perovskite photovoltaic materials from a theoretical perspective. We discuss design of lead-free perovskite materials, humidity-induced degradation mechanisms and possible origins for the observed solar cell hysteresis, and assess future research directions for advanced perovskite solar cells based on computational materials design and theoretical understanding of intrinsic properties.

Multifunctional Perovskite Photodetectors: From Molecular-Scale Crystal Structure Design to Micro/Nano-scale Morphology Manipulation

Multifunctional photodetectors boost the development of traditional optical communication technology and emerging artificial intelligence fields, such as robotics and autonomous driving. However, the current implementation of multifunctional detectors is based on the physical combination of optical lenses, gratings, and multiple photodetectors, the large size and its complex structure hinder the miniaturization, lightweight, and integration of devices. In contrast, perovskite materials have achieved remarkable progress in the field of multifunctional photodetectors due to their diverse crystal structures, simple morphology manipulation, and excellent optoelectronic properties. In this review, we first overview the crystal structures and morphology manipulation techniques of perovskite materials and then summarize the working mechanism and performance parameters of multifunctional photodetectors. Furthermore, the fabrication strategies of multifunctional perovskite photodetectors and their advancements are highlighted, including polarized light detection, spectral detection, angle-sensing detection, and selfpowered detection. Finally, the existing problems of multifunctional detectors and the perspectives of their future development are presented.

Progress in hole-transporting materials for perovskite solar cells

In recent years the photovoltaic community has witnessed the unprecedented development of perovskite solar cells（PSCs） as they have taken the lead in emergent photovoltaic technologies. The power conversion efficiency of this new class of solar cells has been increased to a point where they are beginning to compete with more established technologies. Although PSCs have evolved a variety of structures, the use of hole-transporting materials（HTMs） remains indispensable. Here, an overview of the various types of available HTMs is presented. This includes organic and inorganic HTMs and is presented alongside recent progress in associated aspects of PSCs, including device architectures and fabrication techniques to produce high-quality perovskite films. The structure, electrochemistry, and physical properties of a variety of HTMs are discussed, highlighting considerations for those designing new HTMs. Finally, an outlook is presented to provide more concrete direction for the development and optimization of HTMs for highefficiency PSCs.

Truxene-based Hole-transporting Materials for Perovskite Solar Cells

Three star-shaped truxene-based small molecules（namely TXH,TXM,TXO） were synthesized,characterized and used as hole-transporting materials（HTMs） for perovskite solar cells（Pv SCs）. The device based on TXO delivered a respectable power conversion efficiency（PCE） of 7.89% and a high open-circuit voltage（Voc） of 0.97 V,which far exceeded the values of the devices based on other two small molecules. The highest PCE for the device based on TXO is mainly contributed from its lowest series resistance（Rs） value and largest short-circuit current（Jsc） value under the same circumstances. All these results indicate that TXO is a promising HTM candidate for Pv SCs.

One-dimensional perovskite-based Li-ion battery anodes with high capacity and cycling stability

Perovskite,widely used in solar cells,has also been proven to be potential candidate for effective energy storage material.Recent progress indicates the promise of perovskite for battery applications,however,the specific capacity of the resulting lithium-ion batteries must be further increased.Here,by adjusting the dimensionality of perovskite,we fabricated high-performing one-dimensional hybrid perovskite C_(4)H_(20)N_(4)PbBr_(6) based lithium-ion batteries,with the first specific capacity as high as 1632.8 mAh g^(-1)and a stable specific capacity of 598.0 mAh g^(-1)after 50 cycles under the condition of the constant current density of 150 mA g^(-1).The stable specific capacity is 2.36 times higher than that of the three-dimensional perovskite CH_(3)NH_(3)PbBr_(3)(253.2 mAh g^(-1)),and 1.6 times higher than that of the commercialized graphite electrode(372 mAh g^(-1)).The structure difference and the associated ion diffusivity are revealed to substantially affect the specific capacity of the perovskite-based lithium-ion battery.Our study opens up new directions for the applications of hybrid perovskites in energy storage devices.

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.

A novel phenoxazine-based hole transport material for efficient perovskite solar cell

Based on the previous research work in our laboratory, we have designed and synthesized a small-molecule, hole transport material （HTM） POZ6-2 using phenoxazine （POZ） as central unit and dicyanovinyl units as electron-withdrawing terminal groups. Through the introduction ofa 2-ethyl-hexyl bulky chain into the POZ core unit, POZ6-2 exhibits good solubility in organic solvents. In addition, POZ6-2 possesses appropriate energy levels in combination with a high hole mobility and conductivity in its pristine form. Therefore, it can readily be used as a dopant-flee HTM in perovskite solar cells （PSCs） and a conversion efficiency of 10.3% was obtained. The conductivity of the POZ6-2 layer can be markedly enhanced via doping in combination with typical additives, such as 4-tert-butylpyridine （TBP） and lithium bis（trifluoromethanesulfonyl） imide （LiTFS1）. Correspondingly, the efficiency of the PSCs was further improved to 12.3% using doping strategies. Under the same conditions, reference devices based on the well-known HTM Spiro-OMeTAD show an efficiency of 12.8%.

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.

High efficiency ETM-free perovskite cell composed of CuSCN and increasing gradient CH_(3)NH_(3)PbI_(3)

To enhance device performance and reduce fabrication cost,a series of electron transporting material(ETM)-free perovskite solar cells(PSCs)is developed by TCAD Atlas.The accuracy of the physical mode of PSCs is verified,due to the simulations of PEDOT:PSS-CH_(3)NH_(3)PbI_(3)-PCBM and CuSCN-CH_(3)NH_(3)PbI_(3)-PCBM p-i-n PSCs showing a good agreement with experimental results.Different hole transporting materials(HTMs)are selected and directly combined with n-CH_(3)NH_(3)PbI_(3),and the CuSCN-CH_(3)NH_(3)PbI_(3) is the best in these ETM-free PSCs.To further study the CuSCN-CH_(3)NH_(3)PbI_(3) PSC,the influences of back electrode material,gradient band gap,thickness,doping concentration,and bulk defect density on the performance are investigated.Energy band and distribution of electric field are utilized to optimize the design.As a result,the efficiency of CuSCN-CH_(3)NH_(3)PbI_(3) PSC is achieved to be 26.64%.This study provides the guideline for designing and improving the performances of ETM-free PSCs.

Titanylphthalocyanine as hole transporting material for perovskite solar cells

Titanylphthalocyanine （TiOPc） as hole transporting material （HTM） was successfully synthesized by a simple process with low cost. Perovskite solar cells using the TiOPc as HTM were fabricated and characterized. TiOPc as HTM plays an important role in increasing the power conversion efficiency （PCE） by minimizing recombi- nation losses at the perovskite/Au interface because TiOPc as HTM can extract photogenerated holes from the perovskite and then transport quickly these charges to the back metal electrode. In the research, the β-TiOPc gives a higher PCE than α-TiOPc for the devices due to sufficient transfer dynamics, The β-TiOPc was applied in perovskite solar cells without clopping to afford an impressive PCE of 5.05% under AM 1.5G illumination at the thickness of 40 nm which is competitive with spiro-OMeTAD at the same condition. The present work suggests a guideline for optimizing the photovoltaic properties ofperovskite solar cells using the TiOPc as the HTM.

Luminescent metal-halide perovskites:fundamentals,synthesis,and light-emitting devices

Metal-halide perovskites have garnered considerable research attention as highly efficient light emitters in recent years due to their outstanding optoelectronic properties with remarkable tunability and excellent solution processabilities.Substantial advancements have been achieved in the development of novel halide perovskites,and the exploitations of these materials in lightemitting devices.This review comprehensively outlines recent breakthroughs in metal-halide perovskites,encompassing the rational design of perovskite materials with tunable light emission properties,the controllable growth of single crystal for a deeper understanding of their structure-property relationships,as well as the fundamental insights into the photophysics and carrier dynamics in perovskite systems.Additionally,it provides an overview of recent applications of perovskite materials in high-performance light-emitting diodes(LEDs)and lasers.

Recent progress in perovskite solar cells:material science

Perovskite solar cells represent a promising third-generation photovoltaic technology with low fabrication cost and high power conversion efficiency.In light of the rapid development of perovskite materials and devices,a systematic survey on the latest advancements covering a broad range of related work is urgently needed.This review summarizes the recent major advances in the research of perovskite solar cells from a material science perspective.The discussed topics include the devices based on different type of perovskites(organic-inorganic hybrid,all-inorganic,and lead-free perovskite and perovskite quantum dots),the properties of perovskite defects,different type of charge transport materials(organic,polymeric,and inorganic hole transport materials and inorganic and organic electron transport materials),counter electrodes,and interfacial materials used to improve the efficiency and stability of devices.Most discussions focus on the key progresses reported within the recent five years.Meanwhile,the major issues limiting the production of perovskite solar cells and the prospects for the future development of related materials are discussed.

Regulating Zn Deposition via an Artificial Solid–Electrolyte Interface with Aligned Dipoles for Long Life Zn Anode

Aqueous zinc ion batteries show prospects for next-generation renewable energy storage devices.However,the practical applications have been limited by the issues derived from Zn anode.As one of serious problems,Zn dendrite growth caused from the uncontrollable Zn deposition is unfavorable.Herein,with the aim to regulate Zn deposition,an artificial solid–electrolyte interface is subtly engineered with a perovskite type material,BaTiO3,which can be polarized,and its polarization could be switched under the external electric field.Resulting from the aligned dipole in BaTiO3 layer,zinc ions could move in order during cycling process.Regulated Zn migration at the anode/electrolyte interface contributes to the even Zn stripping/plating and confined Zn dendrite growth.As a result,the reversible Zn plating/stripping processes for over 2000 h have been achieved at 1 mA cm^(−2) with capacity of 1 mAh cm−2.Furthermore,this anode endowing the electric dipoles shows enhanced cycling stability for aqueous Zn-MnO2 batteries.The battery can deliver nearly 100%Coulombic efficiency at 2 Ag^(−1) after 300 cycles.

Recent advances in the design of dopant-free hole transporting materials for highly efficient perovskite solar cells

Continuous success has been achieved for solution-processed inorganic-organic hybrid perovskite solar cells（PVSCs） in the past several years, in which organic charge transporting materials play an important role. At present, most of the commonly used hole-transporting materials（HTMs） such as spiro-OMeTAD derivatives for PVSCs require additional chemical doping process to ensure sufficient conductivity and shift the Fermi level towards the HOMO level for efficient hole transport and collection. However, this doping process not only increases the complexity and cost of device fabrication, but also decreases the device stability. Thus development of efficient dopant-free HTMs for PVSCs is highly desirable and remains as a major challenge in this field. In this review, we will summarize the recent advances in the molecular design of dopant-free HTMs for PVSCs.

Development of electron and hole selective contact materials for perovskite solar cells

Nowadays,both n-i-p and p-i-n perovskite solar cells（PSCs） device structures are reported to give high performance with photo conversion efficiencies（PCEs） above 20%.The efficiency of the PSCs is fundementally determined by the charge selective contact materials.Hence,by introducing proper contact materials with good charge selectivity,one could potentially reduce interfacial charge recombination as well as increase device performance.In the past few years,copious charge selective contact materials have been proposed.Significant improvements in the corresponding devices were observed and the reported PCEs were close to that of classic Spiro-OMeTAD.This mini-review summarizes the state-of-the-art progress of typical electron/hole selective contact materials for efficient perovskite solar cells and an outlook to their development is made.

Effects of Annealing Temperature on Microstructure and Sensing Properties to Alcohol for Nano-La_(0.68)Pb_(0.32)FeO_3

La_(0.68)Pb_(0.32)FeO_3 samples annealed at different temperature were prepared using citrate sol-gel method. With increasing of annealing temperature from 200 to 1000 ℃, the samples crystallize to have single-phase perovskite structure. However, the sensitivity increases at first due to the improvement of crystallization of the perovskite phase, and finally drops attributed to the larger grain size. The optimal sensitivities for La_(0.68)Pb_(0.32)FeO_3 samples annealed at 400, 600, 800, and 1000 ℃ are 12.14, 14.77, 51.07, and 34.55, respectively.

Organic functional materials based buffer layers for efficient perovskite solar cells

In this review, we highlight the recent development of organic π-functional materials as buffer layers in constructing efficient perovskite solar cells（PVSCs）. By following a brief introduction on the PVSC development, device architecture and material design features, we exemplified the exciting progresses made in field by exploiting organic π-functional materials based hole and electron transport layers（HTLs and ETLs） to enable high-performance PVSCs.