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M‐series molecules are one kind of promising acceptor‐donor‐acceptor (A‐D‐A)‐type acceptors for constructing high‐performance organic solar cells (OSCs). However, their power conversion efficiencies (PCEs) are lagging behind that of current state‐of‐the‐art OSCs, limited by the relatively low fill factor (FF) and photocurrent. Herein, combined strategies of layer‐by‐layer (LBL) deposition and interface engineering are conducted to systematically improve light utilization and thus PCEs for M36‐based OSCs. Through choosing a proper processing solvent, a PCE of 17.3% with an FF of 77.9% is achieved for the resulting LBL devices, much higher than those (15.9%/74.0%) from the blend‐casting devices. The improvement is assigned to the favorable morphological evolution that facilitates carrier generation and transport as well as reduces charge recombination. More importantly, light‐harvesting of the active layers can be enhanced upon employing a self‐assembled monolayer of (2‐(9H‐carbazol‐9‐yl)ethyl)phosphonic acid (2PACz) instead of the widely used PEDOT:PSS as the hole‐selecting layer, due to the decreased parasitic absorption of the former. Consequently, 2PACz‐based LBL devices exhibit significantly increased photocurrent, affording a PCE up to 18.2%, which is the highest among the reported A‐D‐A‐type acceptor‐based OSCs. These results deliver important strategies to enhance the performance of OSCs and thus highlight the great potential of M‐series acceptors for practical applications. [ABSTRACT FROM AUTHOR]

Aqueous Zinc–Iodine (Zn–I2) batteries are promising candidates as energy storage system because of their high safety and low cost, but their application is hindered by the dendrite growth, the hydrogen evolution reaction (HER) and corrosion, the shuttle and self‐discharge effect of I3− at electrode/electrolyte interface. Inspired by self‐recognition mechanism of Zn supplement for human body, a self‐recognition layer (SR) is in situ constructed on Zn surface through the coordination of chondroitin sulfate (CHS) molecules with Zn2+ ions and Zn metal, which can induce the uniform Zn2+ deposition via the self‐recognition of Zn2+, suppress the HER and corrosion via physical shielding, as well as restrain the self‐discharge effect of I3− ions via electrostatic repulsion. The in situ SR affords the highly reversible plating/stripping for 9000 h. Remarkably, Zn–I2 full batteries with SR achieve long cycling‐life of 16 000 cycles, which is verified by pouch cell with stable charge/discharge capacity of ≈130 mAh g−1 for 200 cycles. This bionic self‐recognition methodology opens novel avenues to design the optimal electrode/electrolyte interface for high‐performance Zn–I2 batteries. [ABSTRACT FROM AUTHOR]

Antimony chalcogenides films and devices have drawn much attention in recent years because of their notable advantages. Unfortunately, the performance of Sb‐based solar cells is still underdeveloped compared to the theoretical value, which is closely related to charge carrier separation and transfer, highlighting the importance of enhancing the interface quality. In this work, an interfacial engineering by utilizing a self‐assembled monolayer (SAM) of MeO‐2PACz as an interface layer between the Sb2S3 and Spiro‐OMeTAD is developed to assist hole transport. The strong interface interaction between Sb2S3 and MeO‐2PACz is systematically investigated by Raman, X‐ray photoelectron spectroscopy (XPS) measurements, and Density functional theory (DFT) calculations. Through such interfacial engineering, a more uniform surface potential, bigger built‐in potential, better energy‐level match as well as outstanding photoelectric properties are achieved. Finally, the champion power conversion efficiency (PCE = 8.06%) of Sb2S3 solar cells with SAMs is inspiringly enhanced by >13%. It is expected that this effort will bring fresh insights and strategies for improving the performance of Sb‐based solar devices. [ABSTRACT FROM AUTHOR]

Recently, lead halide perovskites have emerged as promising photoanode materials for efficient hydrogen production. However, the sluggish kinetics of the oxygen evolution reaction (OER) and interfacial defect‐mediated charge accumulation inevitably result in efficiency loss and degradation of perovskite photoanodes. Herein, a defect‐passivated electron transport layer‐based perovskite photoanode combined with a catalyst layer favorable is introduced for iodide oxidation reaction bearing a small thermodynamic barrier and rapid kinetics compared to OER for efficient solar fuel generation. The resulting perovskite photoanode revealed a saturated photocurrent density of 22.4 mA cm−2 at 0.3 V versus the reversible hydrogen electrode (VRHE) with an impressive onset potential of −0.2 VRHE as well as durability for 225 h in a neutral electrolyte. In addition, an unbiased hydrogen‐production device comprising a perovskite photoanode and Pt coil electrocatalyst is demonstrated, achieving a remarkable solar‐to‐chemical conversion efficiency of 11.45% and stable operation for 25 h. Moreover, a wireless artificial leaf‐structured device realizing solar‐driven hydrogen generation in natural sea water under outdoor sunlight is presented. [ABSTRACT FROM AUTHOR]

Passivation of perovskite crystals is a crucial strategy to improve the efficiency and stability of perovskite solar cells (PSCs). Zwitterions, which contain both positive and negative charges in the molecule, can be used to passivate perovskite crystals. However, these materials strongly interact with each other, resulting in extremely low solubility in common organic solvents. The low solubility of zwitterions hinders the formation of uniform films, which negatively affects perovskite crystal growth. In this study, a liquid‐type zwitterion (LTZ) is synthesized by modulating intermolecular interactions of the zwitterion (3‐(1‐Pyridinio)‐1‐propanesulfonate). By suppressing intermolecular interactions, the solubility and processibility of the zwitterion in common organic solvents are successfully improved. The well‐distributed LTZ‐treated films are obtained, resulting in better electrical properties for the PSCs compared to solid‐type zwitterion‐based devices. With these characteristics, the resulting device achieves a power conversion efficiency of 24.9% with excellent thermal stability (under 60 °C and N2 atmosphere), maintaining over 80% of its initial efficiency for 1968 h. In addition, the PSC module (active area of 32.7 cm2) achieves an improved efficiency of 19.86% with high open‐circuit voltage and fill factor. The results suggest that interface engineering with an LTZ has the potential to fabricate efficient and stable PSCs. [ABSTRACT FROM AUTHOR]

Low‐temperature vanadium‐based zinc ion batteries (LT‐VZIBs) have attracted much attention in recent years due to their excellent theoretical specific capacities, low cost, and electrochemical structural stability. However, low working temperature surrounding often results in retarded ion transport not only in the frozen aqueous electrolyte, but also at/across the cathode/electrolyte interface and inside cathode interior, significantly limiting the performance of LT‐VZIBs for practical applications. In this review, a variety of strategies to solve these issues, mainly including cathode interface/bulk structure engineering and electrolyte optimizations, are categorially discussed and systematically summarized from the design principles to in‐depth characterizations and mechanisms. In the end, several issues about future research directions and advancements in characterization tools are prospected, aiming to facilitate the scientific and commercial development of LT‐VZIBs. [ABSTRACT FROM AUTHOR]

3D printed energy storage materials and devices (3DP‐ESMDs) have become an emerging and cutting‐edge research branch in advanced energy fields. To achieve satisfactory electrochemical performance, energy storage interfaces play a decisive role in burgeoning ESMD‐based 3D printing. Hence, it is imperative to develop effective interface engineering routes toward desirable 3DP‐ESMDs. In this tutorial review, recent advances in interface engineering for 3DP‐ESMDs are comprehensively provided and in‐depth discussion is offered. To begin with, basic interface engineering principles are introduced. Critical interface engineering strategies including 3D printing‐enabled structural design, composition modification, protective layer design, and 3D printed device optimization are then summarized and illustrated, accompanied by a discussion of pioneering work on 3D printed rechargeable batteries and electrochemical capacitors that has been made through significant interface engineering strategies. Finally, perspectives on interface engineering approaches in future 3DP‐ESMDs are presented. [ABSTRACT FROM AUTHOR]

Recently, lead halide perovskites have attracted significant attention as promising absorber materials for photoelectrochemical (PEC) solar water splitting. However, charge‐accumulation‐induced ion migration at the interface causes perovskite degradation and efficiency loss. To suppress the charge accumulation and improve the PEC performance of the perovskite photoanode, a simple interface engineering is proposed by decorating the SnO2/perovskite interface with a mixture of polyethylenimine ethoxylated (PEIE) and chlorobenzenesulfonic acid (CBSA). The mixed CBSA+PEIE treatment effectively passivates the oxygen vacancies in SnO2 and adjusts the band alignment between SnO2 and the perovskite. The synergistic effects of the mixture treatment facilitate an effective carrier extraction at the SnO2/perovskite interface, enhance the PEC performance, and improve the stability of the device. The perovskite photoanode exhibits an impressive applied bias photon‐to‐current efficiency of 12.9% with an outstanding durability for 225 h. Furthermore, an unbiased solar water splitting is achieved using all the perovskite photoelectrodes, resulting in a remarkable unassisted solar‐to‐hydrogen efficiency of 10.9% and a continuous 22 h stable operation. [ABSTRACT FROM AUTHOR]

Interfacial defects are one of the main origins of the hysteresis effect and limit the efficiency and light stability of perovskite solar cells (PSCs). Herein, the authors propose to grant the hole‐transport materials' (HTMs) improved isotropic coordination and defect passivation through simple halogenation, enabling a robust perovskite/hole‐transport layer interface while avoiding the use of an external passivation layer. First‐principles simulations and experimental results show that the halogenated HTMs offer more isotropic coordination sites for Pb2+ ions than the halogen‐free ones, thus providing the enhanced passivating ability of defects regardless of their molecular orientation at the surface of perovskite films. Consequently, the PSCs based on the chlorinated spiro[fluorene‐9,9′‐xanthene]‐based HTM show suppressed nonradiative recombination, delivering a remarkable open‐circuit voltage (VOC) enhancement (from 1.07 to 1.14 V) and a minimal hysteresis index of as low as 0.07%. The corresponding cells also show much improved light stability, retaining 81% of the initial efficiency after 1000 h of continuous illumination at the maximum power point. This work demonstrates that a solid isotropic coordination capability of HTMs with Pb2+ is critical to forming a robust interface and improving the PSCs' light stability. [ABSTRACT FROM AUTHOR]

Engineering of the interface between perovskite absorber thin films and charge transport layers has fueled the development of perovskite solar cells (PSCs) over the past decade. For p‐i‐n PSCs, the development and adoption of hole transport layers utilizing self‐assembled monolayers (SAM‐HTLs) based on carbazole functional groups with phosphonic acid anchoring groups has enabled almost lossless contacts, minimizing interfacial recombination to advance power conversion efficiency in single‐junction and tandem solar cells. However, so far these materials have been deposited exclusively via solution‐based methods. Here, for the first time, vacuum‐based evaporation of the most common carbazole‐based SAM‐HTLs (2PACz, MeO‐2PACz, and Me‐4PACz) is reported. X‐ray photoelectron spectroscopy and infrared spectroscopy demonstrate no observable chemical differences in the evaporated SAMs compared to solution‐processed counterparts. Consequently, the near lossless interfacial properties are either preserved or even slightly improved as demonstrated via photoluminescence measurements and an enhancement in open‐circuit voltage. Strikingly, applying evaporated SAM‐HTLs to complete PSCs demonstrates comparable performance to their solution‐processed counterparts. Furthermore, vacuum deposition is found to improve perovskite wetting and fabrication yield on previously non‐ideal materials (namely Me‐4PACz) and to display conformal and high‐quality coating of micrometer‐sized textured surfaces, improving the versatility of these materials without sacrificing their beneficial properties. [ABSTRACT FROM AUTHOR]

Over the past few years, all‐inorganic perovskite solar cells (PSCs), especially CsPbI2Br PSCs, have received much attention because of their excellent thermal stability and a suitable trade‐off between light absorption and higher phase stability among the family of inorganic perovskites. In this progress report, the realization of highly efficient and stable CsPbI2Br PSCs is summarized through preparation process, additive engineering, interface modification, and transport material selection. Furthermore, the application of CsPbI2Br in tandem solar cells and its large‐area development are highlighted. Finally, the challenges and outlook of CsPbI2Br PSCs are discussed for further performance improvement and future practical deployment. [ABSTRACT FROM AUTHOR]

Introducing dielectric materials is a promising approach to mitigate space‐charge‐layer (SCL) formation, which negatively affects the electrochemical performance of sulfide‐based all‐solid‐state batteries (ASSBs). Most previous studies have focused on mitigating SCL formation by introducing dielectric materials, overlooking the fact that significant dielectric properties such as the dipole moment direction and the magnitude of the dielectric constant can influence SCL formation. To clarify the unclear mechanism of dielectric materials mitigating SCL formation, paraelectricity, ferroelectricity, and the magnitude of the dielectric constant are investigated to determine their effect on SCL formation. Paraelectric materials possessing no permanent dipole moment can effectively mitigate the SCL formation better than ferroelectric material with strong permanent dipole moment because of the intrinsic characteristics of the paraelectric material, in which the dipole moment can be aligned along the direction of the electric field applied inside of ASSB. Furthermore, paraelectric materials with a larger dielectric constant have a greater effect in mitigating SCL effect than paraelectric materials with a smaller dielectric constant. Thus, these properties should be considered in cathode‐solid‐electrolyte interface design. This study considers relevant dielectric material characteristics that had not been considered previously, suggesting a new paradigm for optimizing the interfacial resistance of sulfide‐based ASSBs originating from SCL formation. [ABSTRACT FROM AUTHOR]

Lead sulfide colloidal quantum dot solar cells (CQDSCs), the next generation of photovoltaics, are hampered by non‐radiative recombination induced by defects and an electron‐hole extraction imbalance. CQDSCs have three interfaces: CQD/CQD, electron transport layer (ETL)/CQD, and CQD/hole transport layer (HTL), and modifying one of these interfaces does not fix the problem stated above. Here, coordinated control and passivation of the three interfaces in PbS CQDSCs are presented and it is shown that the synergistic effects may improve charge transport and charge carrier extraction balance and minimize non‐radiative recombination simultaneously. A facile method is developed for epitaxially growing an ultrathin perovskite shell on the CQD surface to passivate the CQD/CQD interface, resulting in CQD absorber layers with long carrier diffusion lengths. With the introduction of organic films with adjustable electrical characteristics, the influence of ETL/CQD interfacial modifications on carrier transport and recombination is investigated. An excessive increase in the electron extraction rate reduces the fill factor and solar efficiency, as discovered. Therefore a modified layer is created at the CQD/HTL interface to promote hole extraction, which enhances charge extraction balance and passivates the interface. Finally, PbS CQDSCs exhibit a power conversion efficiency of 15.45%, a record for Pb chalcogenide CQDSCs. [ABSTRACT FROM AUTHOR]

Interface engineering plays a vital role in the further improvement of efficiency and stability for organic solar cells (OSCs). Herein, a self‐assembly metal chelate based on hafnium and a designed ligand, N‐(4‐(3‐oxobutanoyl)phenyl)acetamide (ACBN) is applied as both interfacial modification layer and UV‐light filter in OSCs. The strong hydrogen‐bond induced intermolecular interaction enables Hf(ACBN)4 with the prerequisite of adequate solvent resistance to work as an electron transport layer (ETL) in the inverted OSCs. The self‐assembly behavior of Hf(ACBN)4 on the SnO2 film surface via constructing compact coordination structure has been verified via systematic theory calculations. In addition to optimizing the energy level alignment, the Hf(ACBN)4 modification effectively passivates the surface defect of SnO2 films for less surface charge recombination and a more efficient charge collection process. Thus, the OSCs with Hf(ACBN)4 layer yield a maximum PCE of 18.1%, better than that based on the bare SnO2 layer. Moreover, beneficial from the reduced oxygen vacancies via coordination effect and the UV‐light filter function of Hf(ACBN)4, the OSCs based on SnO2/ Hf(ACBN)4 composite ETL exhibit preferable stabilities under UV‐light irradiation or continuous operational conditions. [ABSTRACT FROM AUTHOR]

Battery‐supercapacitor hybrid devices (BSHDs) are aimed to be competitive complements to conventional batteries and supercapacitors by simultaneously achieving high energy density, high power density, and excellent cycling stability. However, the cooperative coupling of different energy storage mechanisms between batteries and supercapacitors is still challenging. Therefore, it is important to have a holistic understanding of BSHDs from material synthesis to final application. In this review, the basic concept and working principles of BSHDs are first discussed, which helps identify the related key scientific problems arising from hybridization. Then the ways in which some of these issues have been mitigated are discussed, for example by developing advanced microstructures and engineering the interface between electrode|current collector, electrode|electrolyte, and battery‐type(b‐type)|capacitor‐type(c‐type) materials. Furthermore, along with shedding light on innovative approaches for expanding the BSHDs' cell voltage unconventional charge‐storage mechanisms and device configurations like dual ion and hydrogen ion hybrid supercapacitors are also summarized to push their performance even higher. Finally, a perspective on the technological challenges and future prospects of BSHDs from both an academic and industrial point of view is provided. This review is expected to serve as a window to look at the past and guide the future development of high‐performance BSHDs. [ABSTRACT FROM AUTHOR]

Interface engineering and passivating contacts are key enablers to reach the highest efficiencies in photovoltaic devices. While printed carbon–graphite back electrodes for hole‐transporting material (HTM)‐free perovskite solar cells (PSCs) are appealing for fast commercialization of PSCs due to low processing costs and extraordinary stability, this device architecture so far suffers from severe performance losses at the back electrode interface. Herein, a 2D perovskite passivation layer as an electron blocking layer (EBL) at this interface to substantially reduce interfacial recombination losses is introduced. The formation of the 2D perovskite EBL is confirmed through X‐ray diffraction, photoemission spectroscopy, and an advanced spectrally resolved photoluminescence microscopy mapping technique. Reduced losses that lead to an enhanced fill factor and VOC are quantified by electrochemical impedance spectroscopy and JSC–VOC measurements. This enables reaching one of the highest reported efficiencies of 18.5% for HTM‐free PSCs using 2D perovskite as an EBL with a significantly improved device stability. [ABSTRACT FROM AUTHOR]

Perovskite single crystals have recently been regarded as emerging candidates for photovoltaic application due to their improved optoelectronic properties and stability compared to their polycrystalline counterparts. However, high interface and bulk trap density in micrometer‐thick thin single crystals strengthen unfavorable nonradiative recombination, leading to large open‐circuit voltage (VOC) and energy loss. Herein, hydrophobic poly(3‐hexylthiophene) (P3HT) molecule is incorporated into a hole transport layer to interact with undercoordinated Pb2+ and promote ion diffusion in a confined space, resulting in higher‐quality thin single crystals with reduced interface and bulk defect density, suppressed nonradiative recombination, accelerated charge transport, and extraction. As a result, a remarkably enhanced VOC of up to 1.13 V and efficiency of 22.1% are achieved, which are both the highest values for MAPbI3 single‐crystal solar cells. Moreover, the reduced defect density and suppressed carrier recombination lead to superior weak light response of the single‐crystal solar cells after incorporation of P3HT, and an indoor photovoltaic efficiency of 39.2% at 1000 lux irradiation is obtained. [ABSTRACT FROM AUTHOR]

Organic–inorganic lead halide perovskite solar cells (PSCs) have demonstrated enormous potential as a new generation of solar‐based renewable energy. Although their power conversion efficiency (PCE) has been boosted to a spectacular record value, the long‐term stability of efficient PSCs is still the dominating concern that hinders their commercialization. Notably, interface engineering has been identified as a valid strategy with extraordinary achievements for enhancing both efficiency and stability of PSCs. Herein, the latest research advances of interface engineering for various interfaces are summarized, and the basic theory and multifaceted roles of interface engineering for optimizing device properties are analyzed. As a highlight, the authors provide their insights on the deposition strategy of interlayers, application of first‐principle calculation, and challenges and solutions of interface engineering for PSCs with high efficiency and stability toward future commercialization. [ABSTRACT FROM AUTHOR]

Emerging semiconducting materials including colloidal quantum dots (CQDs) and organic molecules have unique photovoltaic properties, and their hybridization can result in synergistic effects for high performance. For realizing the full potential of CQD/organic hybrid devices, controlling interfacial properties between the CQD and organic matter is crucial. Here, the electronic band between the CQD and the polymer layers is carefully modulated by inserting an interfacial layer treated with several types of ligands. The interfacial layer provides a cascading conduction band offset (ΔEC), and reduces local charge accumulation at CQD/polymer interfaces, thereby suppressing bimolecular recombination; a thin thiol‐treated interfacial layer (≈6 nm) decreases shallow traps, resulting in higher short‐circuit current (JSC) and fill factor of hybrid solar cells. Based on these results, a high performance CQD/polymer hybrid solar cell is introduced that demonstrates a power conversion efficiency of 13.74% under AM 1.5 solar illumination. The hybrid device retains more than 90% of its initial performance after 402 days under ambient conditions. [ABSTRACT FROM AUTHOR]

Surface engineering of transition metal layered double hydroxides (LDHs) provides an efficient way of enhancing their catalytic activity toward the oxygen evolution reaction (OER). However, the underlying mechanism of atomistic doping or heterogeneous interface with foreign atom is still ambiguous. Herein, a case study of NiFe‐LDHs that are homogeneously doped with Ce (CeNiFe‐LDH) and interfaced with Ce(OH)3 (Ce@NiFe‐LDH), which elucidates their electronic modulation, in situ evolution of active site, and catalytic reaction mechanisms by using X‐ray photoelectronic spectroscopy, operando electrochemical Raman spectroscopy, and first‐principles density functional theory (DFT) calculations, is reported. The results indicate that Ce and Fe atoms serve as the electron acceptors and facilitate the coupled oxidation of Ni3+/4+ in NiFe‐LDH, and the activated oxyhydroxide phase of the catalysts exhibits superior catalytic activity for water oxidation. Especially, Ce@NiFe‐LDH shows a stronger electron transfer between the loaded Ce(OH)3 and the matrix, which leads to a better catalytic activity than CeNiFe‐LDH. DFT calculations provide a clear picture with atomistic resolution for charge redistribution in the NiFe‐LDH surface induced by Ce, which eventually leads to the optimal free energy landscape for the enhanced OER catalytic activity. [ABSTRACT FROM AUTHOR]

Exploring highly active and low‐cost electrocatalysts is essential to the development of sustainable and efficient energy conversion technologies. 2D nanomaterials with unique electronic structure and physicochemical properties have great potential in constructing advanced electrocatalysts. 2D carbonaceous graphene and its analogs (e.g., reduced graphite oxide, carbon nanosheets) have been extensively studied in this field, while there recently has been considerable attention focusing on other 2D metal‐free nanomaterials (e.g., g‐C3N4, h‐BN). Here, the recent advances of 2D metal‐free nanomaterials beyond graphene and its analogs toward a wide range of electrocatalysis applications are reviewed. The strategies for constructing advanced 2D metal‐free nanomaterial‐based electrocatalysts are discussed in terms of surface engineering and interface engineering. Finally, perspectives on the challenges and future directions of these unique material systems in the electrocatalysis area are provided. [ABSTRACT FROM AUTHOR]

Solid‐state lithium batteries (SSLBs) have attracted more attention due to their improved safety and high energy density. Although numerous solid‐state electrolytes (SSEs) with high ionic conductivity have been frequently reported, poor solid–solid interfacial contact and interfacial chemical reactions around the cathode in SSLBs can hinder their practical application. Here, a gradient nanowire (NW) cathode is demonstrated for advanced interface engineering in SSLBs by a facile solvent evaporation process. In this unique gradient cathode membrane, one side surface with more ionic conductive polymer provides a smooth contact with SSE, while the other side surface with more electronic conductive NW/reduced graphene oxide composite provides rapid electron transport acting as a current collector. Furthermore, the inside NW cathode materials are uniformly coated by a solid polymer electrolyte and such a structure changes the point‐to‐point contact to a large‐area contact in the cathode, providing continuous channels for rapid electron/ion transport and improved mechanical strength. The effective interface engineering gives SSLBs enhanced structural stability and excellent electrochemical performance. The as‐obtained SSLBs can deliver 200 mAh g–1 capacity after 100 cycles at room temperature without obvious structural degradation. This novel design of NW‐based gradient cathodes demonstrates a promising strategy for solid–solid interface engineering in solid‐state lithium batteries. [ABSTRACT FROM AUTHOR]

Professor John B. Goodenough started his research on perovskite‐type oxides working on random‐access memory with ceramic [La,M(II)]MnO3 in the Lincoln Laboratory, Massachusetts Institute of Technology, more than 60 years ago. Since then perovskite‐type oxides have played vital roles in the field of energy conversion and storage. In this review, a brief overview is given on the structure, defect chemistry, and transport properties of perovskite oxides, especially the mixed‐valent materials with mixed electronic and ionic conductivities. The recent advances of perovskite oxides applications in the oxygen reduction reaction, oxygen evolution reaction, electrochemical water splitting reaction, metal–air batteries, solid‐state batteries, oxygen separation membranes, and solid oxide fuel cells are highlighted. Moreover, some novel design strategies for optimizing performance, like interface engineering, defect engineering, strain modulation are discussed as well. Finally, a perspective is given on how to design high‐performance perovskite oxide based materials for energy conversion and storage applications as well as the challenges involved in this task. [ABSTRACT FROM AUTHOR]

Due to a certified 25.2% high efficiency, low cost, and easy fabrication; perovskite solar cells (PSCs) are the focus of interest among the next‐generation photovoltaic technologies. Long‐term stability is one of the most challenging obstacles to bring technology from the lab to the market. In this review, applications of self‐assembled monolayers (SAMs) to enhance the power conversion efficiency (PCE) and stability of PSCs is discussed. In the first part, the introduction of SAMs, and deposition techniques applied to different PSC architectures are described. In the middle section, current efforts to utilize SAMs to fine‐tune the optoelectronic properties to enhance the PCE and stability are detailed. The improvements in surface morphology, energy band alignment, as well as reduced interfacial charge recombination induced by SAMs, and the trap passivation mechanism allowing optimal PCE and stability are described. A general outlook summarizing the importance of SAMs to the improvement of PSCs performance is also given, alongside a discussion of future opportunities and possible research directions. [ABSTRACT FROM AUTHOR]

Rational design and construction of bifunctional electrocatalysts with excellent activity and durability is imperative for water splitting. Herein, a novel top‐down strategy to realize a hierarchical branched Mo‐doped sulfide/phosphide heterostructure (Mo‐Ni3S2/NixPy hollow nanorods), by partially phosphating Mo‐Ni3S2/NF flower clusters, is proposed. Benefitting from the optimized electronic structure configuration, hierarchical branched hollow nanorod structure, and abundant heterogeneous interfaces, the as‐obtained multisite Mo‐Ni3S2/NixPy/NF electrode has remarkable stability and bifunctional electrocatalytic activity in the hydrogen evolution reaction (HER)/oxygen evolution reaction (OER) in 1 m KOH solutions. It possesses an extremely low overpotential of 238 mV at the current density of 50 mA cm−2 for OER. Importantly, when assembled as anode and cathode simultaneously, it merely requires an ultralow cell voltage of 1.46 V to achieve the current density of 10 mA cm−2, with excellent durability for over 72 h, outperforming most of the reported Ni‐based bifunctional materials. Density functional theory results further confirm that the doped heterostructure can synergistically optimize Gibbs free energies of H and O‐containing intermediates (OH*, O*, and OOH*) during HER and OER processes, thus accelerating the catalytic kinetics of electrochemical water splitting. This work demonstrates the importance of the rational combination of metal doping and interface engineering for advanced catalytic materials. [ABSTRACT FROM AUTHOR]

Discovery of the 9.7% efficiency, 500 h stable solid‐state perovskite solar cell (PSC) in 2012 triggered off a wave of perovskite photovoltaics. As a result, a certified power conversion efficiency (PCE) of 25.2% was recorded in 2019. Publications on PSCs have increased exponentially since 2012 and the total number of publications reached over 13 200 as of August 2019. PCE has improved by developing device structures from mesoscopic sensitization to planar p‐i‐n (or n‐i‐p) junction and by changing composition from MAPbI3 to FAPbI3‐based mixed cations and/or mixed anion perovskites. Long‐term stability has been significantly improved by interfacial engineering with hydrophobic materials or the 2D/3D concept. Although small area cells exhibit superb efficiency, scale‐up technology is required toward commercialization. In this review, research direction toward large‐area, stable, high efficiency PSCs is emphasized. For large‐area perovskite coating, a precursor solution is equally important as coating methods. Precursor engineering and formulation of the precursor solution are described. For hysteresis‐less, stable, and higher efficiency PSCs, interfacial engineering is one of the best ways as defects can be effectively passivated and thereby nonradiative recombination is efficiently reduced. Methodologies are introduced to minimize interfacial and grain boundary recombination. [ABSTRACT FROM AUTHOR]

Abstract: Perovskite solar cells (PSCs) have advanced quickly with their power conversion efficiency approaching the record of silicon solar cells. However, there is still a big challenge to obtain both high efficiency and long‐term stability for future commercialization of PSCs. The major instability issue is associated with the decomposition or phase transition of perovskite materials that are believed to be intrinsically unstable under outdoor working conditions. Herein, the authors review the approaches that marked important progress in developing new functional electron/hole transporting materials that enabled highly efficient and stable PSCs. The findings that accelerate charge diffusion and that suppress the irrevocable loss of ions diffusing out of perovskite materials and other diffusion processes are highlighted. In addition, derivative interface engineering methods to control the diffusion process of charges/ions/molecules are also reviewed. Finally, the authors propose key research issues in charge transporting materials and interface engineering with regard to the important diffusion processes that will be one of the keys to realize highly efficient and long‐term stable PSCs. [ABSTRACT FROM AUTHOR]

Abstract: A low‐temperature solution‐processed strategy is critical for cost‐effective manufacture of flexible perovskite solar cells (PSCs). Based on an aqueous‐processed TiO2 layer, and conventional fullerene derivatives replaced by a pristine fullerene interlayer of C60, herein a facile interface engineering for making all‐solution‐processed TiO2/C60 layers in flexible n‐i‐p PSCs is reported. Due to the improvement of the perovskite grain quality, promotion of interfacial charge transfer and suppression of interfacial charge recombination, the stabilized power conversion efficiency for the flexible PSCs reaches as high as 16% with high bending resistance retention (≈80% after 1500 cycles) and high light‐soaking retention (≈100% after 100 min). In addition, the stabilized efficiency is over 19% for the rigid TiO2/C60‐based PSCs. The present work with the facile low‐temperature solution process renders the practicability for high‐performance flexible PSCs applied to wearable devices, portable equipment, and electric vehicles. [ABSTRACT FROM AUTHOR]

Abstract: To solve the stability issues of perovskite solar cells (PSC), here a novel interface engineering strategy that a versatile ultrathin 2D perovskite (5‐AVA)2PbI4 (5‐AVA = 5‐ammoniumvaleric acid) passivation layer that is in situ incorporated at the interface between (FAPbI3)0.88(CsPbBr3)0.12 and the hole transporting CuSCN is reported. Surface analysis using X‐ray photoelectron spectroscopy confirms the formation of 2D perovskite. Hysteresis is reduced by the interfacial 2D layer, which could be ascribed to improvement of interfacial charge extraction efficiency, associated with suppression of recombination. Moreover, introduction of the interface passivating layer enhances the moisture stability and photostability as compared to the control perovskite film due to hydrophobic nature of 2D perovskite. The unencapsulated device retains 98% of the initial power conversion efficiency (PCE) after 63 d under moisture exposure of about 10% in the dark. A PCE of the control device is boosted from 13.72 to 16.75% as a consequence of enhanced open‐circuit voltage (Voc) and fill factor along with slightly increased short‐circuit current density (Jsc), which results from reduced trap states of (FAPbI3)0.88(CsPbBr3)0.12 as evidenced by enhanced carrier lifetimes and charge extraction. The perovskite/hole transport material interface engineering gives insight into simultaneous improvements of PCE and device stability. [ABSTRACT FROM AUTHOR]

Abstract: Compact TiO2 is widely used as an electron transport material in planar‐perovskite solar cells. However, TiO2‐based planar‐perovskite solar cells exhibit low efficiencies due to intrinsic problems such as the unsuitable conduction band energy and low electron extraction ability of TiO2. Herein, the planar TiO2 electron transport layer (ETL) of perovskite solar cells is modified with ionic salt CuI via a simple one‐step spin‐coating process. The p‐type nature of the CuI islands on the TiO2 surface leads to modification of the TiO2 band alignment, resulting in barrier‐free contacts and increased open‐circuit voltage. It is found that the polarity of the CuI‐modified TiO2 surface can pull electrons to the interface between the perovskite and the TiO2, which improves electron extraction and reduces nonradiative recombination. The CuI solution concentration is varied to control the electron extraction of the modified TiO2 ETL, and the optimized device shows a high efficiency of 19.0%. In addition, the optimized device shows negligible hysteresis, which is believed to be due to the removal of trap sites and effective electron extraction by CuI‐modified TiO2. These results demonstrate the hitherto unknown effect of p‐type ionic salts on electron transport material. [ABSTRACT FROM AUTHOR]

Abstract: Organic‐inorganic halide perovskite materials have become a shining star in the photovoltaic field due to their unique properties, such as high absorption coefficient, optimal bandgap, and high defect tolerance, which also lead to the breathtaking increase in power conversion efficiency from 3.8% to over 22% in just seven years. Although the highest efficiency was obtained from the TiO2 mesoporous structure, there are increasing studies focusing on the planar structure device due to its processibility for large‐scale production. In particular, the planar p‐i‐n structure has attracted increasing attention on account of its tremendous advantages in, among other things, eliminating hysteresis alongside a competitive certified efficiency of over 20%. Crucial for the device performance enhancement has been the interface engineering for the past few years, especially for such planar p‐i‐n devices. The interface engineering aims to optimize device properties, such as charge transfer, defect passivation, band alignment, etc. Herein, recent progress on the interface engineering of planar p‐i‐n structure devices is reviewed. This review is mainly focused on the interface design between each layer in p‐i‐n structure devices, as well as grain boundaries, which are the interfaces between polycrystalline perovskite domains. Promising research directions are also suggested for further improvements. [ABSTRACT FROM AUTHOR]

Abstract: The interface between the catalyst layer (CL) and the polymer electrolyte membrane (PEM) in a fuel cell has substantial impact on its electrochemical performance. In consequence, there have been growing research activities to engineer this interface to improve the performance of polymer electrolyte membrane fuel cells (PEMFCs). This review summarizes these novel approaches and compares the various techniques. Based on available fuel cell data in the literature, a quantitative comparison of relative improvements due to a micro‐ and nano‐engineered PEM|CL interface is provided. This allows several conclusions: First, regardless of the applied method, a re‐engineering of the PEM|CL interface leads to an improvement of power‐determining parameters, such as mass transport resistances. The latter has hitherto not been clearly connected to the PEM|CL interface and is an important piece of information for future fuel cell development. Second, for patterned membrane surfaces, feature sizes of about 1–10 µm on the membrane surface seem to result in the most significant power density improvement. Third, an engineered PEMCL interface can contribute to extend the fuel cell durability due to enhanced adhesion and contact between the two layers. With this, novel membrane electrode assemblies (MEAs) can be designed that enable significantly higher power densities compared conventional 2D‐layer MEAs. [ABSTRACT FROM AUTHOR]

Hybrid organic/inorganic perovskite solar cells are invigorating the photovoltaic community due to their remarkable properties and efficiency. However, many perovskite solar cells show an undesirable current-voltage ( I- V) hysteresis in their forward and reverse voltage scans, working to the detriment of device characterization and performance. This hysteresis likely arises from slow ion migration in the bulk perovskite active layer to interfaces which may induce charge trapping. It is shown that interfacial chemistry between the perovskite and charge transport layer plays a critical role in ion transport and I- V hysteresis in perovskite-based devices. Specifically, phenylene vinylene polymers containing cationic, zwitterionic, or anionic pendent groups are utilized to fabricate charge transport layers with specific interfacial ionic functionalities. The interfacial-adsorbing boundary induced by the zwitterionic polymer in contact with the perovskite increases the local ion concentration, which is responsible for the observed I- V hysteresis. Moreover, the ion adsorbing properties of this interface are exploited for perovskite-based memristors. This fundamental study of I- V hysteresis in perovskite-based devices introduces a new mechanism for inducing memristor behavior by interfacial ion adsorption. [ABSTRACT FROM AUTHOR]

In this work, both anode and cathode interfaces of p-i-n CH3NH3PbI3 perovskite solar cells (PVSCs) are simultaneously modified to achieve large open-circuit voltage (Voc) and fill factor (FF) for high performance semitransparent PVSCs (ST-PVSCs). At the anode, modified NiO serves as an efficient hole transport layer with appropriate surface property to promote the formation of smooth perovskite film with high coverage. At the cathode, a fullerene bisadduct, C60(CH2)(Ind), with a shallow lowest unoccupied molecular orbital level, is introduced to replace the commonly used phenyl-C61-butyric acid methyl ester (PCBM) as an alternative electron transport layer in PVSCs for better energy level matching with the conduction band of the perovskite layer. Therefore, the Voc, FF and power conversion efficiency (PCE) of the PVSCs increase from 1.05 V, 0.74 and 16.2% to 1.13 V, 0.80 and 18.1% when the PCBM is replaced by C60(CH2)(Ind). With the advantages of high Voc and FF, ST-PVSCs are also fabricated using an ultrathin transparent Ag as cathode, showing an encouraging PCEs of 12.6% with corresponding average visible transmittance (AVT) over 20%. These are the highest PCEs reported for ST-PVSCs with similar AVTs paving the way for using ST-PVSCs as power generating windows. [ABSTRACT FROM AUTHOR]

Poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) is widely used as hole injection/extraction material in organic optoelectronics. However, there still exist drawbacks for PEDOT:PSS such as low work function (WF), poor structural and electrical homogeneity. To solve these problems, methylnaphthalene sulfonate formaldehyde condensate (MNSF) is applied, which has excellent dispersion property, branched chemical structure, and low cost, as dispersant and dopant instead of linear PSS to prepare PEDOT:MNSF. The hole injection/extraction capability of PEDOT:MNSF is systematically studied in organic optoelectronic devices. PEDOT:MNSF-1:6 exhibits unexpected high device performance with a maxima current efficiency of 33.4 cd A−1 in blue phosphorescent organic light-emitting diode and a power conversion efficiency of 13.1% in CH3NH3PbI xCl3− x-based inverted perovskite solar cell, respectively. Compared with PEDOT:PSS, the relatively higher efficiency of PEDOT:MNSF-1:6 is attributed mainly to its higher WF of 5.29 eV, structural and electrical homogeneity. Our research displays a promising future of MNSF as a cheap and widely available alternative of PSS. Moreover, a clear map is provided for the design of dopant for PEDOT considering the structure of dopant. [ABSTRACT FROM AUTHOR]

The electrodes in energy storage devices, such as lithium/sodium ion batteries, are typical multicomponent system consisting of inorganic electrode particles, polymer binders, conductive fillers, current collectors, and other components. These components are usually porously combined by a polymeric binder to accomplish the required electrochemical functions. In spite of the great success, this classic porous configuration faces serious issues in mechanical stability and flexibility due to weak and instable structures/interfaces. Here, by learning from polymeric nanocomposites, a concept of electrode matrix is proposed based on a gum-like nanocomposite, a dual-conductive adhesive. As an electrode matrix, the gum-like nanocomposite integrates the functions of binder, electrolyte, and conductive fillers. In particular, it shows strong adhesion, high electrical/ionic conductivities, and appropriate mechanical and self-healing properties. Finally, it is demonstrated that, with the electrode matrix, battery electrodes can be fabricated into nonporous composite showing not only excellent mechanical flexibility/stability but also improved electrochemical performance when working with a gum-like electrolyte. [ABSTRACT FROM AUTHOR]

Poly(Phenylene vinylene) anionic polyelectrolyte (PVBT‐SO3) was found to be an efficient hole extraction layer for inverted perovskite solar cells. It can be cast from an aqueous solution and does not require thermal annealing for improved device performance. The devices show maximum solar cell efficiency of 15.9% and exhibit improved stability under ambient conditions and enhanced charge extraction. [ABSTRACT FROM AUTHOR]

Plasmonic manipulation of light in metal/semiconductor heterostructures is a powerful tool that exploits extraordinary optical properties of metallic nanostructures to concentrate and control light at the nanometer scale. Here, recent progresses in the mechanism and strategies developed for the control of plasmon-induced optical field distribution, hot electron injection and energy transfer at the metal/semiconductor heterostructure interface are discussed. This is of crucial importance to the selection of matched materials, the design of optimized device architectures and the future development of efficient fabrication technologies for plasmon-enhanced photocatalytic and photovoltaic applications. [ABSTRACT FROM AUTHOR]

Interface engineering is critical for achieving efficient solar cells, yet a comprehensive understanding of the interface between a metal electrode and electron transport layer (ETL) is lacking. Here, a significant power conversion efficiency (PCE) improvement of fullerene/perovskite planar heterojunction solar cells from 7.5% to 15.5% is shown by inserting a fulleropyrrolidine interlayer between the silver electrode and ETL. The interface between the metal electrode and ETL is carefully examined using a variety of electrical and surface potential techniques. Electrochemical impedance spectroscopy (EIS) measurements demonstrate that the interlayer enhances recombination resistance, increases electron extraction rate, and prolongs free carrier lifetime. Kelvin probe force microscopy (KPFM) is used to map the surface potential of the metal electrode and it indicates a uniform and continuous work function decrease in the presence of the fulleropyrrolidine interlayer. Additionally, the planar heterojunction fullerene/perovskite solar cells are shown to have good stability under ambient conditions. [ABSTRACT FROM AUTHOR]

Inverted polymer solar cells with a maximum efficiency of 9.23% are fabricated using a dual functional fullerene zwitterion as the cathode interlayer. C60‐sulfobetaine acts as an electron acceptor and cathode modification layer. Exceptional insensitivity to interlayer thickness is found with efficiencies exceeding 8%. Slot‐die coated solar cells with an organic cathode interlayer have efficiencies of 7.38%. [ABSTRACT FROM AUTHOR]

High efficiency and stable polymer solar cells (PSCs) are fabricated by using solution‐processed Zn1‐xMgxO (ZMO) films as a novel class of cathode buffer layers (CBLs). They have the advantages of tunable bandgaps and energy levels, high optical transparency, and good electron‐transporting abilities. PSCs with an optimized ZMO CBL exhibit a high power conversion efficiency of 8.31%, which is much better than those of control devices without a CBL or with a ZnO CBL. [ABSTRACT FROM AUTHOR]

Advanced thermoelectric technologies can drastically improve energy efficiencies of industrial infrastructures, solar cells, automobiles, aircrafts, etc. When a thermoelectric device is used as a solid-state heat pump and/or as a power generator, its efficiency depends pivotally on three fundamental transport properties of materials, namely, the thermal conductivity, electrical conductivity, and thermopower. The development of advanced thermoelectric materials is very challenging because these transport properties are interrelated. This paper reviews the physical mechanisms that have led to recent material advances. Progresses in both inorganic and organic materials are summarized. While the majority of the contemporary effort has been focused on lowering the lattice thermal conductivity, the latest development in nanocomposites suggests that properly engineered interfaces are crucial for realizing the energy filtering effect and improving the power factor. We expect that the nanocomposite approach could be the focus of future materials breakthroughs. [ABSTRACT FROM AUTHOR]