Strong hetero-interface interaction in 2D/2D WSe_(2)/ZnIn_(2)S_(4) heterostructures for highly-efficient photocatalytic hydrogen generation

Green hydrogen is urgently required for sustainable development of human beings and rational construction of heterostructures holds great promising for photocatalytic hydrogen generation.Herein,2D/2D WSe_(2)/ZnIn_(2)S_(4) heterostructures with strong hetero-interface interaction and abundant contact were constructed via an impregnation-annealing strategy.Efficient charge transfer from ZnIn_(2)S_(4) to WSe_(2)was evidenced by transient absorption spectroscopy in crafted heterostructures owing to the tight and2D face-to-face contact.As a result,the prepared WSe_(2)/ZnIn_(2)S_(4) heterostructures exhibited boosted photocatalytic performance and a highest hydrogen evolution rate of 3.377 mmol/(g h)was achieved with an apparent quantum yield of 45.7%at 420 nm.The work not only provides new strategies to achieve efficient 2D/2D heterostructures but also paves the way for the development of green hydrogen in the future.

Unraveling Passivation Mechanism of Imidazolium-Based Ionic Liquids on Inorganic Perovskite to Achieve Near-Record-Efficiency CsPbI_(2)Br Solar Cells

The application of ionic liquids in perovskite has attracted wide-spread attention for its astounding performance improvement of perovskite solar cells(PSCs).However,the detailed mechanisms behind the improvement remain mysterious.Herein,a series of imidazolium-based ionic liquids(IILs)with different cations and anions is systematically investigated to elucidate the passivation mechanism of IILs on inorganic perovskites.It is found that IILs display the following advantages:(1)They form ionic bonds with Cs^(+)and Pb^(2+)cations on the surface and at the grain boundaries of perovskite films,which could effectively heal/reduce the Cs^(+)/I−vacancies and Pb-related defects;(2)They serve as a bridge between the perovskite and the hole-transport-layer for effective charge extraction and transfer;and(3)They increase the hydrophobicity of the perovskite surface to further improve the stability of the CsPbI_(2)Br PSCs.The combination of the above effects results in suppressed non-radiative recombination loss in CsPbI_(2)Br PSCs and an impressive power conversion efficiency of 17.02%.Additionally,the CsPbI_(2)Br PSCs with IILs surface modification exhibited improved ambient and light illumination stability.Our results provide guidance for an indepth understanding of the passivation mechanism of IILs in inorganic perovskites.

Recent Progress of Electrode Materials for Flexible Perovskite Solar Cells

Flexible perovskite solar cells(FPSCs) have attracted enormous interest in wearable and portable electronics due to their high power-per-weight and low cost. Flexible and efficient perovskite solar cells require the development of flexible electrodes compatible with the optoelectronic properties of perovskite. In this review, the recent progress of flexible electrodes used in FPSCs is comprehensively reviewed. The major features of flexible transparent electrodes, including transparent conductive oxides, conductive polymer, carbon nanomaterials and nanostructured metallic materials are systematically compared. And the corresponding modification strategies and device performance are summarized. Moreover, flexible opaque electrodes including metal films, opaque carbon materials and metal foils are critically assessed. Finally, the development directions and difficulties of flexible electrodes are given.

Flexible perovskite solar cells based on green,continuous roll-to-roll printing technology

By designing and fabricating thin film electronic devices on a flexible substrate instead of more commonly used rigid substrate, flexible electronics produced has opened a field of special applications. In this article, we first reviewed available products that may be used as flexible substrates, their characteristics and unique advantages as supporting material for flexible electronic devices. Secondly, flexible perovskite solar cell is examined in detail, with special focus on its potential large-scale fabrication processes. In particular, a comprehensive review is provided on low cost solution printing techniques that is viewed highly as a viable tool for potential commercialization of the perovskite solar cells. Furthermore, a summary is given on green processing for the solution printing production of flexible perovskite devices.

Fabrication of nanoporous Ni and NiO via a dealloying strategy for water oxidation catalysis

Nickel oxides and(oxy)hydroxides are promising replacements for noble-metal-based catalysts owing to their high activity and good long-term stability for the oxygen evolution reaction(OER). Herein, we developed nanoporous Ni by a method of combined rapid solidification and chemical dealloying. Subsequently,nanoporous Ni O was obtained via heating treatment, the macropore and skeleton sizes of the NiO originated from Ni10Al90 alloy are 100–300 nm and 80–200 nm, respectively. Benefiting from the multi-stage nanoporous structure and high specific surface area, the nanoporous NiO demonstrates an outstanding OER, reaching 20 mA cm-2 at an overpotential of 356 mV in 1 M KOH. The corresponding Tafel slope and apparent activation energy are measured to be 76.73 mV dec-1 and 29.0 kJ mol-1, respectively. Moreover,kinetic analysis indicates that the Ni O catalyst shows pseudocapacitive characteristics, and the improved current is attributed to the high-rate pseudocapacitive behavior that efficiently maintains increased nickel redox cycling to accelerate the reaction rates. After 1000 cycles of voltammetry, the overpotential of the NiO decreases by 22 mV(j = 10 mA cm-2), exhibiting excellent stability and durability.

A Special Additive Enables All Cations and Anions Passivation for Stable Perovskite Solar Cells with Efficiency over 23%

Passivating undercoordinated ions is an effective way to reduce the defect densities at the surface and grain boundaries(GBs)of perovskite materials for enhanced photovoltaic performance and stability of perovskite solar cells(PSCs).Here,(BBF)complex is chosen as a multifunctional additive,which contains both C7H9N and BF3 groups working as Lewis base and Lewis acid,respectively,can bond with Pb^(2+)/I^(−) and FA+on the surface and in the GBs in the perovskite film,affording passivation of both cation and anion defects.The synergistic effect of the C7H9N and BF3 complex slows the crystallization during the perovskite film deposition to improve the crystalline quality,which reduces the trap density and the recombination in the perovskite film to suppress nonradiative recombination loss and minimizes moisture permeation to improve the stability of the perovskite material.Meanwhile,such an additive improves the energy-level alignment between the valence band of the perovskite and the highest occupied molecular orbital of the hole-transporting material,Spiro-OMeTAD.Consequently,our work achieves power conversion efficiency of 23.24%,accompanied by enhanced stability under ambient conditions and light illumination and opens a new avenue for improving the performance of PSCs through the use of a multifunctional complex.

Secondary crystallization strategy for highly efficient inorganic CsPbI_(2)Br perovskite solar cells with efficiency approaching 17%

Inorganic CsPbI_(2) Br perovskite solar cells(PSCs) have a tremendous development in last few years due to the trade-off between the excellent optoelectronic properties and the relatively outstanding stability.Herein,we demonstrated a strategy of secondary crystallization(SC) for CsPbI_(2) Br film in a facile planar n-i-p structure(ITO/ZnO-SnO_(2)/CsPbI_(2) Br/Spiro-OMeTAD/Ag) at low-temperature(150℃).It is achieved through the method of post-treatment with guanidinium bromine(GABr) atop annealed CsPbI_(2) Br film.It was found that the secondary crystallization by GABr can not only regulate the crystal growth and passivate defects,but also serve as a charge collection center to effectively collect photogenerated carriers.In addition,due to the excess Br ions in GABr,the formation of the Br-rich region at the CsPbI_(2) Br perovskite surface can further lower the Fermi level,leading to more beneficial band alignment between the perovskite and the hole transport layer(HTL),while the phase stability was also improved.As a result,the champion cell shows a superb open-circuit voltage(V_(oc)) of 1.31 V,a satisfactory power conversion efficiency(PCE) of 16.97% and outstanding stabilities.As far as we know,this should be one of the highest PCEs reported among all-inorganic CsPbI_(2) Br based PSCs.

Perspective on the imaging device based on perovskite materials

Large light absorption coefficients,tunable bandgaps,high tolerance to defects,long carrier lifetimes as well as diffusion lengths render lead halide perovskite materials ideal candidates for optoelectronic devices.Except application in solar cell,photodetectors based on perovskite materials have been recognized as another game changer due to the achievements such as high responsivity of 1.9×104 A/W[1],gain factor larger than 5.0×104[1],large detectivity of 1014 J[2],high on/off ratio of 105[3],fastest response time down to 1 ns[4],large linear dynamic range exceeding 170[5]and low detachable light intensity as small as 1 pW/cm2[6],which demonstrate the potential applications of perovskite based photodetector in the areas of weak light detection.

Anthradithiophene based hole-transport material for efficient and stable perovskite solar cells

A novel hole-transport material(HTM)based on an anthradithiophene central bridge named BTPA-7 is developed.In comparison to spiro-OMeTAD(2,2’,7,7’-tetrakis-(N,N-di-p-methoxyphenylamine)-9,9’-spirobifluorene),the synthetic steps of BTPA-7 are greatly reduced from 6 to 3 and the synthetic cost of BTPA-7 is nearly a half that of spiro-OMeTAD.Moreover,BTPA-7 exhibits a relatively lower conductivity but higher hole mobility and higher glass transition temperature(Tg)than spiro-OMeTAD.Compared with the photovolatic performance for spiro-OMeTAD,FA0.85MA0.15PbI3 and MAPbI3 PSC devices based on BTPA-7 exhibit slightly lower PCEs with the values of 17.58%(18.88%for spiro-OMeTAD)and 11.90%(13.25%for spiro-OMeTAD),respectively.Nevertheless,a dramatically higher JSC of PSC based on BTPA-7is achieved,which arises from the higher hole mobility of BTPA-7.In addition,the relatively hydrophobic character of BTPA-7 eventually enhances the PSC device stability.Lower cost,higher hole mobility,higher Tg,satisfactory photovoltaic performance,and superior device stability of BTPA-7 can be utilized as a substitute for spiro-OMeTAD in PSCs.

Double Side Interfacial Optimization for Low-Temperature Stable CsPbI_(2)Br Perovskite Solar Cells with High Efficiency Beyond 16%

CsPbI_(2)Br perovskite solar cells have achieved rapid development owing to their exceptional optoelectronic properties and relatively outstanding stability.However,open-circuit voltage(Voc)loss caused by band mismatch and charge recombination between perovskite and charge transporting layer is one of the crucial obstacles to further improve the device performance.Here,we proposed a bilayer electron transport layer ZnO(bottom)/SnO_(2)(top)to reduce the Voc loss(Eloss)and promote device Voc by ZnO insert layer thickness modulation,which could improve the efficiency of charge carrier extraction/transfer and suppress the charge carrier recombination.In addition,guanidinium iodide top surface treatment is used to further reduce the trap density,stabilize the perovskite film and align the energy levels,which promotes the fill factor,short-circuit current density(Jsc),and stability of the device.As a result,the champion cell of double-side optimized CsPbI_(2)Br perovskite solar cells exhibits an extraordinary efficiency of 16.25%with the best Voc as high as 1.27 V and excellent thermal and storage stability.

The issues on the commercialization of perovskite solar cells

Perovskite solar cells have aroused a worldwide research upsurge in recent years due to their soaring photovoltaic performance,ease of solution processing,and low cost.The power conversion efficiency record is constantly being broken and has recently reached 26.1%in the lab,which is comparable to the established photovoltaic technologies such as crystalline silicon,copper indium gallium selenide and cadmium telluride(CdTe)solar cells.Currently,perovskite solar cells are standing at the entrance of industrialization,where huge opportunities and risks coexist.However,towards commercialization,challenges of up-scaling,stability and lead toxicity still remain,the proper handling of which could potentially lead to the widespread adoption of perovskite solar cells as a low-cost and efficient source of renewable energy.This review gives a holistic analysis of the path towards commercialization for perovskite solar cells.A comprehensive overview of the current state-of-the-art level for perovskite solar cells and modules will be introduced first,with respect to the module efficiency,stability and current status of industrialization.We will then discuss the challenges that get in the way of commercialization and the corresponding strategies to address them,involving the upscaling,the stability and the lead toxicity issue.Insights into the future direction of commercialization of perovskite photovoltaics was also provided,including the flexible perovskite cells and modules and perovskite indoor photovoltaics.Finally,the future perspectives towards commercialization are put forward.

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.

Epitaxial growth of large-area and highly crystalline anisotropic ReSe2 atomic layer

The anisotropic two-dimensional （2D） layered material rhenium disulfide （ReSe2） has attracted considerable attention because of its unusual properties and promising applications in electronic and optoelectronic devices. However, because of its low lattice symmetry and interlayer decoupling, anisotropic growth and out-of-plane growth occur easily, yielding thick flakes, dendritic structure, or flower-like structure. In this stud34 we demonstrated a bottom-up method for the controlled and scalable synthesis of ReSe2 by van der Waals epitaxy. To achieve controllable growth, a micro-reactor with a confined reaction space was constructed by stacking two mica substrates in the chemical vapor deposition system. Within the confined reaction space, the nucleation density and growth rate of ReSe2 were significantly reduced, favoring the large-area synthesis of ReSe2 with a uniform monolayer thickness. The morphological evolution of ReSe2 with growth temperature indicated that the anisotropic growth was suppressed at a low growth temperature （〈600 ℃）. Field-effect transistors employing the grown ReSe2 exhibited p-type conduction with a current ON/OFF ratio up to 10s and a hole carrier mobility of 0.98 cm^2/（V·s）. Furthermore, the ReSe2 device exhibited an outstanding photoresponse to near-infrared light, with responsivity up to 8.4 and 5.1 A/W for 850- and 940-nm light, respectively. This work not only promotes the large-scale application of ReSe2 in high-performance electronic devices but also clarifies the growth mechanism of low-lattice symmetry 2D materials.

High detectivity photodetectors based on perovskite nanowires with suppressed surface defects

Solution-processable,single-crystalline perovskite nanowires are ideal candidates for developing low-cost photodetectors,but their detectivities are limited due to a high level of unintentional defects.Through the surfaceinitiated solution-growth method,we fabricated high-quality,single-crystalline,defects-suppressed MAPbI_(3) nanowires,which possess atomically smooth side surfaces with a surface roughness of 0.27 nm,corresponding to a carrier lifetime of 112.9 ns.By forming ohmic MAPbI_(3)∕Au contacts through the dry contact method,highperformance metal–semiconductor–metal photodetectors have been demonstrated with a record large linear dynamic range of 157 dB along with a record high detectivity of 1.2×10^(14) Jones at an illumination power density of 5.5 nW∕cm^(2).Such superior photodetector performance metrics are attributed to,first,the defects-suppressed property of the as-grown MAPbI_(3) nanowires,which leads to a quite low noise current in the dark,and second,the ohmic contact between MAPbI_(3) and Au interfaces,which gives rise to an improved responsivity compared with the Schottky contact counterpart.The realized high-performance MAPbI_(3) nanowire photodetector advances the development of low-cost photodetectors and has potential applications in weak-signal photodetection.

A leap towards high performance quantum dot solar cells

Lead halide perovskites in the form of nanocrystalline quantum dots(QDs)have emerged as a new class of semiconductor materials for photovoltaics(PVs)and optoelectronics.Thanks to the nanoscale size-induced lattice strain and enhanced contribution from the surface energy[1],perovskite QDs have shown superior phase stability at room temperature over their thin film bulk counterparts offering a promising strategy to significantly increase stability and hence lifetime of the perovskite devices.

Flexible Diodes/Transistors Based on Tunable p-n-Type Semiconductivity in Graphene/Mn-Co-Ni-O Nanocomposites

We report a novel Mn-Co-Ni-O(MCN)nanocomposite in which the p-type semiconductivity of Mn-Co-Ni-O can be manipulated by addition of graphene.With an increase of graphene content,the semiconductivity of the nanocomposite can be tuned from p-type through electrically neutral to n-type.The very low effective mass of electrons in graphene facilitates electron tunneling into the MCN,neutralizing holes in the MCN nanoparticles.XPS analysis shows that the multivalent manganese ions in the MCN nanoparticles are chemically reduced by the graphene electrons to lower-valent states.Unlike traditional semiconductor devices,electrons are excited from the filled graphite band into the empty band at the Dirac points from where they move freely in the graphene and tunnel into the MCN.The new composite film demonstrates inherent flexibility,high mobility,short carrier lifetime,and high carrier concentration.This work is useful not only in manufacturing flexible transistors,FETs,and thermosensitive and thermoelectric devices with unique properties but also in providing a new method for future development of 2D-based semiconductors.

Flexible Diodes/Transistors Based on Tunable p-n-Type Semiconductivity in Graphene/Mn-Co-Ni-O Nanocomposites

We report a novel Mn-Co-Ni-O(MCN)nanocomposite in which the p-type semiconductivity of Mn-Co-Ni-O can be manipulated by addition of graphene.With an increase of graphene content,the semiconductivity of the nanocomposite can be tuned from p-type through electrically neutral to n-type.The very low effective mass of electrons in graphene facilitates electron tunneling into the MCN,neutralizing holes in the MCN nanoparticles.XPS analysis shows that the multivalent manganese ions in the MCN nanoparticles are chemically reduced by the graphene electrons to lower-valent states.Unlike traditional semiconductor devices,electrons are excited from the filled graphite band into the empty band at the Dirac points from where they move freely in the graphene and tunnel into the MCN.The new composite film demonstrates inherent flexibility,high mobility,short carrier lifetime,and high carrier concentration.This work is useful not only in manufacturing flexible transistors,FETs,and thermosensitive and thermoelectric devices with unique properties but also in providing a new method for future development of 2D-based semiconductors.

国家三要素及未来形态的建构——超越政治与市场的理想共同体

国家包含着政治、经济和社会三大要素,基于三大要素形成了各种不同形态的国家模式,政治导致权力垄断及其不平等,经济导致资本控制和社会排斥,而社会则基于友爱精神带来团结互助,基于社会要素可以形成一种超越政治与市场的理想共同体类型,即橄榄型的社会性国家.