Recent progress of hybrid cathode interface layer for organic solar cells

Organic solar cells(OSCs)have gained conspicuous progress during the past few decades due to the development of materials and upgrading of the device structure.The power conversion efficiency(PCE)of the single-junction device had surpassed 19%.The cathode interface layer(CIL),by optimizing the connection between the active layer and the cathode electrode,has become a momentous part to strengthen the performances of the OSCs.Simultaneously,CIL is also indispensable to illustrating the working mechanism of OSCs and enhancing the stability of the OSCs.In this essay,hybrid CILs in OSCs have been summarized.Firstly,the advancement and operating mechanism of OSCs,and the effects and relevant design rules of CIL are briefly concluded;secondly,the significant influence of CIL on enhancing the stability and PCE of OSCs is presented;thirdly,the characteristics of organic hybrid CIL and organic-inorganic hybrid CIL are introduced.Finally,the conclusion and outlook of CIL are summarized.

Ionic Liquid Assisted Imprint for Efficient and Stable Quasi-2D Perovskite Solar Cells with Controlled Phase Distribution

Although two-dimensional perovskite devices are highly stable,they also lead to a number of challenges.For instance,the introduction of large organic amines makes crystallization process complicated,causing problems such as generally small grain size and blocked charge transfer.In this work,imprint assisted with methylamine acetate were used to improve the morphology of the film,optimize the internal phase distribution,and enhance the charge transfer of the perovskite film.Specifically,imprint promoted the dispersion of spacer cations in the recrystallization process with the assistance of methylamine acetate,thus inhibited the formation of low-n phase induced by the aggregation of spacer cations and facilitated the formation of 3D-like phase.In this case,the corresponding quasi-2D perovskite solar cells delivered improved efficiency and exhibited superior stability.Our work provides an effective strategy to obtain uniform phase distribution for quasi-2D perovskite.

Realizing high-performance organic solar cells through precise control of HOMO driving force based on ternary alloy strategy

A good deal of studies have proven that effective exciton dissociation and fast hole transport can operate efficiently in non-fullerene organic photovoltaics(OPVs)despite nearly zero driving force.Even so,whether such a phenomenon is universal and how small the driving force can realize the best photovoltaic performance still require a thorough understanding.Herein,despite the zero driving force based on PM6:F8IC system,a maximum short-circuit current(J_(sc))of 23.0 mA/cm^(2) and high power conversion efficiency(PCE)of 12.2%can still be achieved.Due to the continuously adjustable energy levels can be realized in organic semiconducting alloys including F8IC:IT-4F and F8IC:Y6,the suitable third components can play the role of energy level regulator.Therefore,the HOMO energy level offset(DEHOMO(D A))from zero to 0.07 and 0.06 eV is accomplished in the optimized IT-4F and Y6 ternary devices.Consequently,both ternary devices achieved substantially increased PCE of 13.8%and Jsc of 24.4 and 25.2 mA/cm^(2),respectively.Besides,pseudo-planar heterojunction(PPHJ)devices based on alloyed acceptors through sequential spin-coating method further improve the photovoltaic performance.Our work puts forward the concept of energy level regulator and prove that the ternary alloy strategy has unique advantages and huge research potential in continuously adjusting the driving force.

Highly crystalline acceptor materials based on benzodithiophene with different amount of fluorine substitution on alkoxyphenyl conjugated side chains for organic photovoltaics

Organic solar cells based on narrow bandgap small-molecule acceptors(SMAs)with highly crystalline characteristics have attracted great attentions for their superiority in obtaining high photovoltaic efficiency.Employing highly crystalline SMAs to enhance power conversion efficiencies(PCEs)by regulating and controlling morphology and compatibility of donor and acceptor materials has turned out to be an effective approach.In this study,we synthesized three different crystalline SMAs by using fluorine substitution on alkoxyphenyl conjugated side chains to modulate the relationship of crystallinity and morphologies,namely ZY1(zero F atoms),ZY2(two F atoms),and ZY3(four F atoms).The three SMAs show the broad absorption edges and similar frontier orbital energy levels,generating the analogical(over 0.9 V)open circuit voltage(VOC)of the polymer solar cells(PSCs).As a result,the PM6:ZY2-based PSCs yield a PCE of 10.81%with a VOC of 0.95 V,a short-circuit current density(JSC)of 16.154 mA cm^(-2),and a fill factor(FF)of 0.71,which is higher than that of 9.17%(PM6:ZY1)and 6.37%(PM6:ZY3).And the PCE(17.23%)of the PM6:Y6:ZY2 based ternary PSCs is also higher than that of 16.32%PM6:Y6 based binary device.Obviously,the results demonstrate that adding fluorine atoms on the conjugated side chains to construct high crystalline materials is a positive strategy to effectively increase the efficiencies of binary and ternary PSCs.

Atmospheric stable and fexible Sn-based perovskite solar cells via a bioinspired antioxidative crystal template

Sn-based perovskite solar cells(PSCs)demonstrate a potential development in eco-friendly devices due to their hypotoxicity.However,poor stability and crystalline quality are still the challenges for achieving high-performance and long-term operating devices.In this work,inspired by biological protein,nickelporphyrin(Ni-P)with electron cloud on conjugate ring is applied into Sn-based perovskite to prevent perovskite from being eroded.The synergistic effect of water and oxygen is broken in grain boundaries and surface so that the stability of PSCs can be improved obviously,despite there is hardly any barrier for water to erode.Simultaneously,the electron-rich molecules can passivate the defects of perovskite such as iodine vacancy.Moreover,the ester group in Ni-P molecule can bind with SnI;to form complex and then restrain nucleation.Combining with the template effect of 2D molecular,the crystallization of perovskite films is optimized.Therefore,the Sn-based PSCs with Ni-P achieve a stabilized power conversion efficiency(PCE)of 7.79%with negligible hysteresis in fexible devices,respectively.Moreover,the PSCs can maintain 80%of the pristine PCE after 300 h under air environment.

Non-conjugated terpolymer acceptors for highly efficient and stable lager-area all-polymer solar cells

All-polymer solar cells(all-PSCs)have made significant progress recently,but few studies have been conducted to investigate the lab-to-manufacturing translation from the spin-coating method to the printing process.Here,the random copolymerization method and non-conjugated backbone approach are integrated to manipulate the morphology and photoelectric properties of the active layer for large-area printed all-PSCs.A series of non-conjugated terpolymer acceptors PYSe-TC_(6)T(x)(x=5,10,and 20,refers to the molar ratio of TC_(6)T unit)are developed by covalently introducing non-conjugated unit TC_(6)T into the PYSe host bipolymer by random copolymerization.The spin-coated PYSe-TC_(6)T(10)-based all-PSC demonstrates the best power conversion efficiency(PCE)of 13.54%,superior to the PYSe-based one(12.45%).More intriguingly,morphological studies reveal that a combination of the random polymerization and non-conjugated backbone strategy can effectively prevent the active layer from overaggregation and improve the film quality during the printing process,thereby minimizing the efficiency and technology gap between spin-coated small-area devices and blade-coated large-area devices.By directly using the same preparation condition of spin-coating,the blade-coated small-area(0.04 cm^(2))delivers a PCE of 12.83%and the large-area(1.21 cm^(2))device achieves a PCE of 11.96%with a small PCE loss.Both PCE value and PCE loss are one of the most outstanding performances of the bladecoated all-PSCs.These findings reveal that a combination of the non-conjugated flexible backbone with random copolymerization to develop non-conjugated terpolymers is an attractive design concept to smoothly realize the lab-to-manufacturing translation.

Preparation of Perovskite Solar Cells in the Air:Degradation Mechanism and Prospects on Large-Area Fabrication

The preparation of perovskite solar cells(PsCs)in the air environment has attracted the attention of numerous experimenters due to its low preparation cost and the possibility of commercialization.Although the power conversion efficiency(PCE)of PSCs has increased rapidly and exceeded 25%,which is comparable to commercial polysilicon solar cells,most certified or reported high-efficiency perovskite solar cells are still confined to glove boxes or relatively small active areas in the air environment due to moisture,oxygen,high temperature,and ultraviolet(UV)factors.In this review.

Highly efficient perovskite solar cells by building 2D/3D perovskite heterojuction in situ for interfacial passivation and energy level adjustment

Passivating the interfacial defects and reducing the interfacial non-radiative recombination losses are the keys to improving the photovoltaic performance of three-dimensional(3D)perovskite solar cells(PVSCs).Stacking two dimensional(2D)perovskites on 3D perovskite is a promising method for interfacial treatment that improves the stability and efficiency of PVSCs.Herein,we developed conjugated fluorinated benzimidazolium cation(FBIm+)which can be inserted between 3D perovskite and holetransporting layer(HTL)to form 2D perovskite in situ.The 2D single crystal structures of(FBIm)_(2)Pb I4and(FBIm)_(2)Pb Br_(4)were achieved and confirmed by single-crystal X-ray diffraction(XRD),while few single crystals of 2D perovskite based on imidazolium or benzimidazolium anchors have been reported.The 2D perovskite can passivate the interfacial defects,induce better crystallinity and orientation,conduct lower trap density and extend carrier lifetime.Furthermore,the energy level arrangement can be regulated by changing the counterion from iodide to bromide,which can efficiently improve the hole extraction and device performances.As a consequence,the best efficiency of 23.00%for FBIm Br-incorporated devices was achieved,while only 20.72%for the control device.Meanwhile,the PVSCs modified by FBIm Br displayed excellent environmental stability due to the constructed hydrophobic 2D perovskite layer which can effectively block moisture permeation.This work develops a new path to design novel conjugated organic passivants to form 2D/3D perovskite structures.

Dual-Resistance of Ion Migration and Moisture Erosion via Hydrolytic Crosslinking of Siloxane Functionalized Poly(Ionic Liquids)for Efficient and Stable Perovskite Solar Cells

The inevitable ion migration that occurs within ionic polycrystalline perovskite film results in inferior longterm stability of perovskite solar cells(PVSCs)that cannot meet the commercial requirements.Here,a novel poly(ionic liquid)named poly-1-vinyl-3-propyltrimethoxysilane imidazolium chloride(PImIL-SiO)is first introduced into perovskite to strengthen grain boundaries(GBs)and construct dual-functional barriers against internal ion migration and external moisture erosion for fabricating highly efficient and stable PVSCs.PImIL-SiO-containing imidazoliumcations and pendant siloxane groups contribute to passivation of bulk defects and anchoring of GBs,which effectively hinders ion migration channels,thus reducing perovskite film phase separation and device hysteresis.Furthermore,the intrinsically hydrophobic PImIL-SiO automatically forms a secondary protective barrier to endow the perovskite film with ultrahigh moisture corrosion resistance through the hydrolyzation reaction of siloxane with the permeated moisture.Consequently,the PImIL-SiO-modified PVSCs achieve a champion power conversion efficiency(PCE)of 22.46%,accompaniedby excellent thermal andhumidity stabilities where the non-encapsulated devices retain 87%of the initial PCE after aging at 85℃for 250 h and>85%of the initial PCE over 1100 h in air with a relative humidity of 50–70%.

Random Terpolymer Based on Simple Siloxane-functionalized Thiophene Unit Enabling High-performance Non-fullerene Organic Solar Cells

Incorporation of siloxane-functionalized units into polymers backbone has proven to be an efficient strategy to improve photovoltaic performance. In this work, a low-cost siloxane-containing unit was developed to construct a series of terpolymers, and the effects of siloxane on the polymer performance were systematically studied. Different contents of thiophene containing siloxane-functionalized side chain were introduced into PM6 to obtain a series of polymers(PM6, PM6-SiO-10, PM6-SiO-20 and PM6-SiO-30). The siloxane-functionalized side chains in polymers have only a slight effect on the absorption behavior and frontier molecular orbitals. However, when the siloxane content increased, the terpolymers' aggregation property decreased and the temperature-dependency increased, leading to improved donor-acceptor compatibility. The power conversion efficiency(PCE) based on PM6:Y6, PM6-SiO-20:Y6 and PM6-SiO-30:Y6 devices was 15.64%, 16.03% and 15.82%, respectively. In comparison, the active layer based on PM6-SiO-10:Y6 exhibits the most appropriate phase separation morphology, resulting in effective exciton dissociation, more balanced hole-electron transport and less recombination. Consequently, the highest PCE of 16.69% with an outstanding shortcircuit current density of 26.96 mA·cm^(-2) was obtained, which are one of the highest values for siloxane-functionalized polymer-based devices.This work demonstrates that finely controlling the content of siloxane-functionalized thiophene is beneficial for obtaining high-performance terpolymer donors and provides a novel and low-cost method to improve photovoltaic performance.

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.

Additive-free non-fullerene organic solar cells with random copolymers as donors over 9% power conversion efficiency

In this study, a series of random conjugated polymers (PBDB-TBTn) as donors were designed and synthesized. In these polymers, benzodithiophene unit with thiophene conjugated side chains (BDT) are donor part, and two different content of benzo[1,2-c:4,5-c']dithiophene-4,8-dione (BDD) and difluorobenzothiadizole (BT) linked alkylthiophene are acceptor unit. Polymer solar cells (PSCs) were fabricated with ITIC as an acceptor, and over the power conversion efficiency (PCE) of 9%was obtained, with open circuit voltage (Voc) of 0.86 V, short-circuit current density (Jsc) of 16.84 mA/cm^2, and fill factor (FF) of 62.5%. These random conjugated polymers based solar cells are insensitive to solvent additives and thermal annealing. The performance of the device decreases gradually with the increasing of the proportion of fluorinated acceptor unit. The declining efficiency is due to the excessive fluorinated acceptor unit, which leads to over aggregated topography, destroys the effective charge transport pathways, and affects phase separation domain size between the donor and the acceptor. The phenomena are explained by the charge carrier recombination, atomic force microscope (AFM), and transmission electron microscope (TEM). These results indicate that proper addition of fluorinated acceptor units to build random copolymers can enhance the efficiency of organic photovoltaics toward additive-free and thermal annealing-free PSCs.

Reducing Energy Loss and Morphology Optimization Manipulated by Molecular Geometry Engineering for Hetero-junction Organic Solar Cells

of main observation and conclusion Molecular geometry engineering is an efective strategy to control the micromorphology and molecularenergy level in organic photovoltaics(OPVs).Two novel copolymers based on alkysilyl-and chloride-functionalied benzodithiophene(BDT)were designed and synthesized for wide bandgap copolymer donor materials in OPVs.It was found that the two copolymers exhited distinctly different proper-ties in active layer when blended with fulerene-fre acceptor T-4.The chloride-functionalited copolymer PBDTCI-TZ2 with deeper molecular energy leveland better coplanar structure induced more ordered aggregation in blend flm.Thus,the device based on PBDTC-TZ exhibits better energy alinmentwith IT-4F and smallr radiative recombination.furthermore,the non-radiative recombination of PBDTCI-TZ.T-4F based device is about 45 mV lowerthan the PBDTS-TZ/T-4F based device,contributing to a lower enery loss(Ein,and a higher open-cicut voltage(Vc).As a resut,the devices based onthe blend of PBDTC-TZ2.IT-4F exhibit a high power conversion efficiency(PCE)of up to 12.2%with a high Vvoe of 0.837 Vv,higher than that of PBDTSi-TZ:IT-4F,of which the PCE is 11.2%with a Voc of 0.781V.

Wide Band-gap Two-dimension Conjugated Polymer Donors with Different Amounts of Chlorine Substitution on Alkoxyphenyl Conjugated Side Chains for Non-fullerene Polymer Solar Cells

In this study,wide bandgap(WBG)two-dimensional(2D)copolymer donors(DZ1,DZ2,and DZ3)based on benzodithiophene(BDT)on alkoxyphenyl conjugated side chains without and with different amounts of chlorine atoms and difluorobenzotriazole(FBTZ)are designed and synthesized successfully for efficient non-fullerene polymer solar cells(PSCs).Three polymer donors DZ1,DZ2,and DZ3 display similar absorption spectra at 300-700 nm range with optional band-gap(Egopt)of 1.84,1.92,and 1.97 eV,respectively.Compared with reported DZ1 without chlorine substitution,it is found that introducing chlorine atoms into the meta-position of the alkoxyphenyl group affords polymer possessing a deeper the highest occupied molecular orbital(HOMO)energy level,which can increase open circuit voltage(Voc)of PSCs,as well as improve hole mobility.Non-fullerene bulk heterojunction PSCs based on DZ2:MelC demonstrate a relatively high power conversion efficiency(PCE)of 10.22%with a Voc of 0.88 V,a short-circuit current density(Jsc)of 17.62 mA/cm^2,and a fill factor(FF)of 68%,compared with PSCs based on DZ1:MelC(a PCE of 8.26%)and DZ3:MelC(a PCE of 6.28%).The results imply that adjusting chlorine atom amount on alkoxyphenyl side chains based on BDT polymer donors is a promising approach of synthesizing electron-rich building block for high performance of PSCs.

Novel polymer acceptors achieving 10.18% efficiency for all-polymer solar cells

Polymer acceptors based on extended fused ring p skeleton has been proven to be promising candidates for all-polymer solar cells(all-PSCs), due to their remarkable improved light absorption than the traditional imide-based polymer acceptors. To expand structural diversity of the polymer acceptors, herein,two polymer acceptors PSF-IDIC and PSi-IDIC with extended fused ring p skeleton are developed by copolymerization of 2,20-((2 Z,20 Z)-((4,4,9,9-tetrahexadecyl-4,9-dihydro-s-indaceno [1,2-b:5,6-b']dithio phene-2,7-diyl)bis(methanylylidene))bis(3-oxo-2,3-dihydro-1 H-indene-2,1-diylidene))dimalononitrile(IDIC-C16) block with sulfur(S) and fluorine(F) functionalized benzodithiophene(BDT) unit and silicon(Si) atom functionalized BDT unit, respectively. Both polymer acceptors exhibit strong light absorption.The PSF-IDIC exhibits similar energy levels and slightly higher absorption coefficient relative to the PSi-IDIC. After blended with the donor polymer PM6, the functional atoms on the polymer acceptors show quite different effect on the device performance. Both of the acceptors deliver a notably high open circuit voltage(V_(OC)) of the devices, but PSi-IDIC achieves higher V OCthan PSF-IDIC. All-PSC based on PM6:PSi-IDIC attains a power conversion efficiency(PCE) of 8.29%, while PM6:PSF-IDIC-based device achieves a much higher PCE of 10.18%, which is one of the highest values for the all-PSCs reported so far. The superior device performance of PM6:PSF-IDIC is attributed to its higher exciton dissociation and charge transport, decreased charge recombination, and optimized morphology than PM6:PSi-IDIC counterpart. These results suggest that optimizing the functional atoms of the side chain provide an effective strategy to develop high performance polymer acceptors for all-PSCs.

Concerted regulation on vertical orientation and film quality of two-dimensional ruddlesden-popper perovskite layer for efficient solar cells

Recently,the two-dimensional(2D)ruddlesden-popper(RPP)perovskite has been successfully attracting great attention owing to their excellent electronic property and superior ambient stability.But 2D perovskite solar cells(PVSCs)with insulating large cations show a worse performance than three-dimensional(3D)PVSCs in general because of the worse charge transportation.In this work,dimethyl sulfoxide(DMSO)and KI were incorporated simultaneously to produce a synergistic effect on both film quality and orientation of 2D perovskite.With this strategy,a cavity-free 2D perovskite film was formed with vertically oriented crystal,and high quality film was obtained with decreased defects and increased crystallinity.Besides,profitable multiple phases were obtained for better spontaneous carrier separation and transportation.The 2D PVSCs based on(PEA)2(MA)n−1PbnI3n+1(n=5)delivered a higher power conversion efficiency(PCE)of 13.4%.In addition,the perovskite with KI and DMSO contained more stable low-dimension phase at the bottom of perovskite film,which could act as a barrier to prevent moisture from further eroding internal perovskites.The optimized 2D PVSCs remained 90%of the PCE after being exposed in air(50%–60%humidity,room temperature)with a continuous illumination for 300 h.

Improving Ultraviolet Stability of Perovskite Solar Cells via Singlet Fission Down-Conversion

The instability of perovskite materials under continuous ultraviolet(UV)light irradiation and high sensitivity in humid environments remain obstacles to future commercialization.Especially,the photovoltaic performance of perovskite solar cells(PVSCs)is prone to decline under UV light exposure for sustained periods of time.However,in conventional methods,preventing UV light from entering PVSCs usually comes at the expense of reducing short circuit photocurrent(Jsc).Herein,the UV stability of PVSCs is modified by in-troducing a singlet fission down-conversion layer 6,13-bis(triisopropylsilylethynyl)pentacene(TIPS-PEN)via one-step anti-solvent method without sacrificing device efficiency.The introduction of down conversion layer can not only improve the Jsc by converting UV light into multiple excitons,but also enhance the open-circuit voltage(Voc)owing to a better matched energy level alignment at the perovskite/spiro-OMeTAD interface.Consequently,the TIPS-PEN incorporated PVSCs attain the champion power conversion effi-ciency(PCE)up to 22.92%accompanied with dramatically increased UV photostability which can retain 80%of its primitive PCE un-der continuous UV light soaking for 150 h.Moreover,the unencapsulated PVSCs with TIPS-PEN exhibit remarkable moisture stability which can sustain over 80%of the initial value under air conditions(50%relative humidity,25℃)after 1000 h.

Selection of Functional Spacer Cations for Efficient 2D/3D Perovskite Solar Cells

In recent years,perovskite solar cells(PSCs)have gone through unparalleled rapid expansion and become a candidate for solar cells.Among various PSCs,though typical three-dimensional(3D)halide perovskite-based PSCs deliver the highest efficiency,they are subjected to severe instability,which constrains their commercializability.In comparison,two-dimensional(2D)PSCs have aroused widespread concern due to their superior stability.After that,2D/3D perovskite materials combining high efficiency and good stability have emerged as the times require,which are expected to bring about stable and efficient PSCs.Here,this review focuses on selection of functional spacer cations for efficient and stable 2D/3D PSCs.First,the unique function of different spacer groups and the selection of appropriate spacer cations in 2D perovskites is summarized and proposed.Then,by selecting appropriate cations,the role of 2D perovskites is elaborated,including energy level regulation,ion migration suppression,defect passivation,residual stress release and improved stability.In addition,the preparation methods of 2D/3D perovskites are comprehensively summarized.Finally,current challenges and future opportunities for the further development of 2D/3D perovskites for solar cells are discussed and prospected.

Contact Electrification Spectrum for Performance Enhancement Mechanism Investigation of Triboelectric Nanogenerators based on Silicone Elastomers with Different Surface Microstructures

Triboelectric nanogenerators(TENGs)based on conjunctive effects of contact electrification(CE)and electrostatic induction are emerging as a new mechanical energy harvesting and sensing technique for promising applications in smart wearables,Internet of Things(IoTs),etc.The surface microstructure of a flexible triboelectric material for the increase of surface area is a common strategy for performance enhancement of TENGs,but the real roles of surface microstructures on their output performance are still not explicit due to the lack of suitable analysis tool and rational experimental design.Taking advantages of the surface-sensitive characteristic of CE effect,this work exploited and developed the electric signal patterns generated by single impact of TENGs as a kind of CE spectrum to analyze and speculate the real roles of surface microstructures of flexible triboelectric materials on the output performance of TENGs.Firstly,four different kinds of surface microstructures,namely planar surface(PS)and three combinations of two basic surface microstructures,i.e.,micro lens arrays(MLAs),fabric textures(FTs),and hierarchical structures of MLAs on FTs(MLA/FTs),were elaborately designed and introduced for an identical triboelectric material(i.e.,silicone elastomer)by a(micro)molding synthesis route.Then they were used for assembly of TENGs based on vertical contact mode to conduct performance evaluation under the same triggering conditions.Through systematic analysis and comparison of their highly repeatable CE spectra by programmed machine,it was found that the surface microstructure for a flexible triboelectric material to maximally enhance the output performance of a TENG shall achieve a positive synergistic effect of increasing triboelectric charge density,effective contact area and contacting/separating velocity,rather than simple increase of its surface area.

Recent Progresses on Dopant-Free Organic Hole Transport Materials toward Efficient and Stable Perovskite Solar Cells

As the third generation new battery,the power conversion efficiency(PCE)of metal halide perovskite solar cells(PsCs)has increased from 3.8%in 2009 to 25.8%currently certified,which fully shows that they have great research value and development prospect.As one of the main components of high-efficiency PSCs,hole transport materials(HTMs)play an important role in extracting and transporting holes and inhibiting charge recombination.However,commonly used HTMs require doping,and the hygroscopicity and corrosiveness of the dopants will destroy the stability of PsCs and hinder their commercialization.Therefore,it is of great significance to develop dopant-free HTMs.