Ion–Electron Coupling Enables Ionic Thermoelectric Material with New Operation Mode and High Energy Density

Ionic thermoelectrics(i-TE) possesses great potential in powering distributed electronics because it can generate thermopower up to tens of millivolts per Kelvin. However,as ions cannot enter external circuit, the utilization of i-TE is currently based on capacitive charge/discharge, which results in discontinuous working mode and low energy density. Here,we introduce an ion–electron thermoelectric synergistic(IETS)effect by utilizing an ion–electron conductor. Electrons/holes can drift under the electric field generated by thermodiffusion of ions, thus converting the ionic current into electrical current that can pass through the external circuit. Due to the IETS effect, i-TE is able to operate continuously for over 3000 min.Moreover, our i-TE exhibits a thermopower of 32.7 mV K^(-1) and an energy density of 553.9 J m^(-2), which is more than 6.9 times of the highest reported value. Consequently, direct powering of electronics is achieved with i-TE. This work provides a novel strategy for the design of high-performance i-TE materials.

Polaron mobility modulation by bandgap engineering in black phaseα-FAPbI_(3)

Lead halide hybrid perovskites(LHP)have emerged as one of the most promising photovoltaic materials for their remarkable solar energy conversion ability.The transportation of the photoinduced carriers in LHP could screen the defect recombination with the help of the large polaron formation.However,the physical insight of the relationship between the superior optical-electronic performance of perovskite and its polaron dynamics related to the electron-lattice strong coupling induced by the substitution engineering is still lack of investigation.Here,the bandgap modulated thin films ofα-FAPbI_(3)with different element substitution is investigated by the time resolved Terahertz spectroscopy.We find the polaron recombination dynamics could be prolonged in LHP with a relatively smaller bandgap,even though the formation of polaron will not be affected apparently.Intuitively,the large polaron mobility in(FAPb I_(3))0.95(MAPbI_(3))0.05thin film is~30%larger than that in(FAPb I_(3))0.85(MAPbBr_(3))0.15.The larger mobility in(FAPb I_(3))0.95(MAPb I_(3))0.05could be assigned to the slowing down of the carrier scattering time.Therefore,the physical origin of the higher carrier mobility in the(FAPb I_(3))0.95(MAPbI_(3))0.05should be related with the lattice distortion and enhanced electron–phonon coupling induced by the substitution.In addition,(FAPbI_(3))0.95(MAPbI_(3))0.05will lose fewer active carriers during the polaron cooling process than that in(FAPb I_(3))0.85(MAPbBr_(3)),indicating lower thermal dissipation in(FAPbI_(3))0.95(MAPbI_(3))0.05.Our results suggest that besides the smaller bandgap,the higher polaron mobility improved by the substitution engineering inα-FAPbI_(3)can also be an important factor for the high PCE of the black phaseα-FAPbI_(3)based solar cell devices.

A chlorinated copolymer donor demonstrates a 18.13% power conversion efficiency

The rapid development of low-bandgap(LBG)nonfullerene acceptors and wide-bandgap(WBG)copolymer donors in recent years has boosted the power conversion efficiency(PCE)of organic solar cells(OSCs)to the 18%level[1−21].The commercialization of OSCs is highly expected.However,critical issues like the cost and the stability also determine whether OSCs can enter the market or not[22].

Annealing-free alcohol-processable MoO_(X) anode interlayer enables efficient light utilization in organic photovoltaics

Molybdenum oxide(MoO_(x))is a commonly used hole extraction material in organic photovoltaics.The MoO_(x) interlayer is deposited typically via thermal evaporation in vacuum.To meet the need for rollto-roll manufacturing,solution processing of MoO_(x) without post-annealing treatment is essential.Herein,we demonstrate an effective approach to produce annealing-free,alcohol-processable MoO_(x) anode interlayers,namely S-MoO_(x),by utilizing the bis(catecholato)diboron(B_(2) Cat_(2))molecule to modify the surface oxygen sites in MoO_(x).The formation of surface diboron-oxygen complex enables the alcohol solubility of S-MoO_(x).An enhanced light utilization is realized in the S-MoO_(x)-based organic photovoltaics.This affords a superior short-circuit current density(Jsc)close to 26 mA cm^(-2) and ultimately a high power-conversion efficiency(PCE)of 15.2%in the representative PM6:Y6 based inverted OPVs,which is one of the highest values in the inverted OPVs using an as-cast S-MoO_(x) anode interlayer.

Editorial for the special issue“Printable solar cells:From materials to devices”

Printable solar cells(including perovskite solar cells and organic photovoltaic cells,etc.)are manufactured based on soluble/dispersible semiconductor materials via printing technologies.They have unique advantages of light weight,flexibility,adjustable color/transparency and low cost.In recent years,great breakthroughs have been made in the field of printable solar cells,and their energy conversion efficiency exceeds 25%,which is comparable to that of monocrystalline silicon solar cells.At present,this novel photovoltaic technology is expected to overcome the commercialization barrier.In this context,Materials Reports:Energy(MRE)specially planned a themed issue on printable solar cells.A number of high-quality papers are collected,aiming to introduce the latest progress in this field and provide a wide overview of theoretical and experimental progress and research results from materials to devices.

Recent progress in hydrogen:From solar to solar cell

Hydrogen,meeting the requirements of sustainable development,is regarded as the ultimate energy in the 21st century.Due to the inexhaustible and feasible of solar energy,solar water splitting is an immensely promising strategy for environmental-friendly hydrogen production,which not only overcomes the fluctuation and intermittency but also contributes to achieving the mission of global“Carbon Neutrality and Carbon Peaking”.However,there is still a lack of a comprehensive overview focusing on hydrogen progress with a discussion of development from solar energy to solar cells.Herein,we emphasize several solar-to-hydrogen pathways from the basic concepts and principles and focus on photovoltaic-electrolysis and photoelectrochemical/photovoltaic systems,which have achieved solar-to-hydrogen(STH)efficiency of over 10%and have extremely promising for large-scale application.In addition,we summarize the challenges and opportunities faced in this field including configuration design,electrode materials,and performance evaluation.Finally,perspectives on the potential commercial application and scientific research for the further development of solar-to-hydrogen are analyzed and presented.

Quasi-Solid Thermoelectrics for Wearable Low-Grade Energy Harvesting

Ionic thermoelectricity(i-TE),as a new energy conversion and storage technology,has been widely discussed by the academic community.As one of the representatives of low-grade thermal energy recovery,i-TE has made remarkable progress and become an influential research direction in the energy field.Among them,thermoelectric ionogels have a wide range of applications in the field of energy recovery and utilization due to their excellent flexibility,stability,and thermoelectric conversion ability,providing many application possibilities for such materials.The development of highly efficient and stable ionic thermoelectric devices is largely dependent on the development of new materials and structural designs.This paper focuses on the recent strategies for improving the efficiency of thermoelectric conversion in the field of ionic thermoelectric gels,including new methods for material design,structural optimization,and innovative developments in the application of thermoelectric materials.The evaluation indicators of thermoelectric conversion efficiency are discussed,including ionic thermal voltage,ionic conductivity and power output,ductility,and self-healing properties.Additionally,various application devices based on thermoelectric materials with excellent thermoelectric conversion properties are highlighted.Further,different challenges and strategies that need to be addressed are presented in the hope of providing inspiration and guidance for the commercialization of i-TE.

Accelerated discovery of novel high-performance zinc-ion battery cathode materials by combining high-throughput screening and experiments

Aqueous zinc ion batteries(AZIBs)have attracted much attention in recent years due to their high safety,low cost,and decent electrochemical performance.However,the traditional electrodes development process requires tedious synthesis and testing procedures,which reduces the efficiency of developing highperformance battery devices.Here,we proposed a high-throughput screening strategy based on firstprinciples calculations to aid the experimental development of high-performance spinel cathode materials for AZIBs.We obtained 14 spinel materials from 12,047 Mn/Zn-O based materials by examining their structures and whether they satisfy the basic properties of electrodes.Then their band structures and density of states,open circuit voltage and volume expansion rate,ionic diffusion coefficient and energy barrier were further evaluated by first-principles calculations,resulting in five potential candidates.One of the promising candidates identified,Mg_(2)MnO_(4),was experimentally synthesized,characterized and integrated into an AZIB based cell to verify its performance as a cathode.The Mg_(2)MnO_(4)cathode exhibits excellent cycling stability,which is consistent with the theoretically predicted low volume expansion.Moreover,at high current density,the Mg_(2)MnO_(4)cathode still exhibits high reversible capacity and excellent rate performance,indicating that it is an excellent cathode material for AZIBs.Our work provides a new approach to accelerate the development of high-performance cathodes for AZIBs and other ion batteries.

18% Efficiency organic solar cells

In 1995,Yu et al.[1]first reported bulk-heterojunction(BHJ)solar cells with a conjugated polymer donor and a fullerene acceptor as the active materials.From then on,BHJ organic solar cells(OSCs)have attracted academic and industrial interests due to the advantages like lightweight,flexibility and roll-to-roll fabrication.Nowadays,17%power conversion efficiencies(PCEs)have been achieved in the state-of-the-art OSCs[2,3].The remarkable progress in OSCs relies on the continuously emerging new materials and device fabrication technologies,and the understanding on film morphology and device physics[4,5].

A 2.16 eV bandgap polymer donor gives 16%power conversion efficiency

Nowadays,wide-bandgap(WBG)copolymers attract great attention in the field of organic photovoltaics[1].They are ideal electron-donating partners for low-bandgap small molecule acceptors[2-12].With good energy levels matching,the blend of WBG copolymer donor and small molecule acceptor can harvest most of the sunlight and deliver high power conversion efficiencies(PCEs)in solar cells.PCEs higher than 16%have been achieved[13-15].WBG copolymers especially those with ultra-wide bandgaps(i.e.,optical bandgap(Eg opt)>2.07 eV,absorption onset<600 nm)can find applications in ternary solar cells[16]and tandem solar cells[17].Currently,ultra-WBG copolymer donors are less efficient,generally giving PCEs below 13%[18].Designing highly efficient ultra-WBG copolymers is needed.In this work,we use fluorine-and alkoxyl-substituted benzene(FAB)as the building block to construct ultra-WBG copolymer donors.

有机太阳电池关键材料研究进展

有机太阳电池具有质量轻、柔性、印刷制备等优点,有巨大的应用潜力,从其诞生那一刻起便引起了学术界和工业界的广泛研究兴趣.历经25年的发展,有机太阳电池效率已突破18%,其快速进步得益于不断涌现的高性能新材料和器件制备技术,以及对电池活性层形貌、分子堆积和器件机理的深入理解.基于有机共轭结构的电子给体和电子受体材料是决定有机太阳电池性能的关键材料.本文将以给、受体材料的发展历程为主线,聚焦那些明星材料和里程碑工作,阐述高性能关键材料的分子结构演变和进化过程,最后展望其面临的挑战和未来发展方向.

外场强化电解水析氢

电解水析氢过程中的能量消耗及析氢效率有很多影响因素,其中,电荷转移电阻和催化剂表面气泡覆盖率是最为重要的两个因素。研究发现,在电解水析氢过程中利用外场进行强化,可以有效减小电荷转移电阻和催化剂表面气泡覆盖率,如温度场能为反应过程中电荷的转移注入能量,从而降低电荷转移电阻,降低过电位;而电场能直接调整催化剂电子结构或诱导电解液离子重新分布,从而促进界面电荷转移;光场则可以诱导水分子极化,增大剩余电场,同时拉伸水分子中氢键,有利于水分解产生氢气和氧气。因此,在电解池中引入温度场、磁场、超声场、电场、超重力场和光场等外场也是降低能耗、提高析氢效率的有效策略。近年来,关于外场强化电解水的研究工作虽有报道,但研究偏少且未见系统性的归纳总结。本文即综述了近年来在电解水析氢过程中利用外场强化的研究进展。介绍各种外场强化电解水析氢的基本原理,同时通过实验案例分析各外场手段的效果,并总结外场强化电解水析氢面临的挑战及发展方向。

Progress of the key materials for organic solar cells

Organic solar cells have attracted academic and industrial interests due to the advantages like lightweight,flexibility and roll-to-roll fabrication.Nowadays,18%power conversion efficiency has been achieved in the state-of-the-art organic solar cells.The recent rapid progress in organic solar cells relies on the continuously emerging new materials and device fabrication technologies,and the deep understanding on film morphology,molecular packing and device physics.Donor and acceptor materials are the key materials for organic solar cells since they determine the device performance.The past 25 years have witnessed an odyssey in developing high-performance donors and acceptors.In this review,we focus on those star materials and milestone work,and introduce the molecular structure evolution of key materials.These key materials include homopolymer donors,D-A copolymer donors,A-D-A small molecular donors,fullerene acceptors and nonfullerene acceptors.At last,we outlook the challenges and very important directions in key materials development.

Over 16% efficiency from thick-film organic solar cells

近年来有机太阳电池效率突飞猛进,单结电池效率已经突破18%,然而这些高效率电池的活性层厚度通常只有100 nm左右,随着厚度增加,电池效率下降明显.为了实现有机太阳电池的产业化,发展对厚度不敏感,且可适用于卷对卷印刷制备的高性能厚膜电池势在必行.本文通过在D18:Y6二元活性层中加入少量富勒烯受体PC61BM,使得电池对厚度的敏感性显著降低. PC61BM的加入使厚膜活性层的电子和空穴迁移率明显提高,载流子传输更加平衡,并且显著降低了陷阱辅助复合.D18:Y6:PC61BM(1:1.6:0.2)三元电池在活性层厚度超过300 nm时,还能保持16%以上的效率,是目前性能最优异的厚膜有机太阳电池之一.

Thiolactone copolymer donor gifts organic solar cells a 16.72% efficiency

Since 1995,bulk-heterojunction organic solar cells consisting of one or two organic donors and one or two organic acceptors have been fighting for high power conversion efficiencies(PCEs)and good stability[1].Until recent years,this next-generation photovoltaic technology starts to offer decent PCEs,shedding the light on commercialization,and attracting great attention again[2-14].Compared w让h the continuously emerging highperformance nonfullerene acceptors,high-performance donors are rare.

CsPb(I_(x)Br_(1-x))_(3) solar cells

Owing to its nice performance, low cost, and simple solution-processing, organic-inorganic hybrid perovskite solar cell(PSC) becomes a promising candidate for next-generation high-efficiency solar cells.The power conversion efficiency(PCE) has boosted from 3.8% to 25.2% over the past ten years. Despite the rapid progress in PCE, the device stability is a key issue that impedes the commercialization of PSCs. Recently, all-inorganic cesium lead halide perovskites have attracted much attention due to their better stability compared with their organic-inorganic counterpart. In this progress report, we summarize the properties of CsPb(IxBr1-x)3 and their applications in solar cells. The current challenges and corresponding solutions are discussed. Finally, we share our perspectives on CsPb(IxBr1-x)3 solar cells and outline possible directions to further improve the device performance.

Tunable luminescent CsPb_2Br_5 nanoplatelets:applications in light-emitting diodes and photodetectors

Unlike organic–inorganic hybrid perovskites, all-inorganic cesium lead halide perovskites hold great promise for developing high-performance optoelectronic devices, owing to their improved stability. Herein, we investigate the perovskite-related CsPb_2 Br_5 nanoplatelets(NPLs) with tunable emission wavelengths via changing the reaction temperatures to 100°C, 120°C, and 140°C. Reaction temperature plays a key role in determining the shapes and thicknesses of the resulting CsPb_2 Br_5 NPLs. A higher temperature is in favor of the formation of smaller and thicker NPLs. To develop their potential applications in optoelectronic devices, green light emitting diodes(LEDs) and photodetectors based on CsPb_2 Br_5 NPLs are fabricated. The green LEDs based on CsPb_2 Br_5 NPLs synthesized at 140°C exhibit an excellent pure green emission(full width at half-maximum of <20 nm) and display a luminous efficiency of 34.49 lm∕W under an operation current of 10 m A. Moreover, the photodetector based on CsPb_2 Br_5 NPLs synthesized at 100°C has better performance with a rise time of 0.426 s, a decay time of0.422 s, and a ratio of the current(with and without irradiation) of 364%.

Block copolymers as efficient cathode interlayer materials for organic solar cells

Emerging needs for the large-scale industrialization of organic solar cells require high performance cathode interlayers to facilitate the charge extraction from organic semiconductors.In addition to improving the efficiency,stability and processability issues are major challenges.Herein,we design block copolymers with well controlled chemical composition and molecular weight for cathode interlayer applications.The block copolymer coated cathodes display high optical transmittance and low work function.Conductivity studies reveal that the block copolymer thin film has abundant conductive channels and excellent longitudinal electron conductivity due to the interpenetrating networks formed by the polymer blocks.Applications of the cathode interlayers in organic solar cells provide higher power conversion efficiency and better stability compared to the most widelyapplied ZnO counterparts.Furthermore,no post-treatment is needed which enables excellent processability of the block copolymer based cathode interlayer.

Self-adhesive and biocompatible dry electrodes with conformal contact to skin for epidermal electrophysiology

Long-term biopotential monitoring requires high-performance biocompatible wearable dry electrodes.But currently,it is challenging to establish a form-preserving fit with the skin,resulting in high interface impedance and motion artifacts.This research aims to present an innovative solution using an all-green organic dry electrode that eliminates the aforementioned challenges.The dry electrode is prepared by introducing biocompatible maltitol into the chosen conductive polymer,poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate).Thanks to the secondary doping and plasticizer effect of maltitol,the dry electrode exhibits good stretchability(62%),strong self-adhesion(0.46 N/cm),high conductivity(102 S/cm),and low Young's modulus(7 MPa).It can always form a conformal contact with the skin even during body movements.Together with good electrical properties,the electrode enables a lower skin contact impedance compared to the current standard Ag/AgCl gel electrode.Consequently,the application of this dry electrode in bioelectrical signal measurement(electromyography,electrocardiography,electroencephalogra-phy)and long-term biopotential monitoring was successfully demonstrated.