Inkjet-Printing Controlled Phase Evolution Boosts the Efficiency of Hole Transport Material Free and Carbon-Based CsPbBr_(3) Perovskite Solar Cells Exceeding 9%

Hole transport material free carbon-based all-inorganic CsPbBr_(3)perovskite solar cells(PSCs)are promising for commercialization due to its low-cost,high open-circuit voltage(V_(oc))and superior stability.Due to the different solubility of PbBr_(2)and CsBr in conventional solvents,CsPbBr_(3)films are mainly obtained by multi-step spin-coating through the phase evolution from PbBr_(2)to CsPb_(2)Br_(5)and then to CsPbBr_(3).The scalable fabrication of high-quality CsPbBr_(3)films has been rarely studied.Herein,an inkjet-printing method is developed to prepare high-quality CsPbBr_(3)films.The formation of long-range crystalline CsPb_(2)Br_(5)phase can effectively improve phase purity and promote regular crystal stacking of CsPbBr_(3).Consequently,the inkjet-printed CsPbBr_(3)C-PSCs realized PCEs up to 9.09%,8.59%and 7.81%with active areas of 0.09,0.25,and 1 cm^(2),respectively,demonstrating the upscaling potential of our fabrication method and devices.This high performance is mainly ascribed to the high purity,strong crystal orientation,reduced surface roughness and lower trap states density of the as-printed CsPbBr_(3)films.This work provides insights into the relationship between the phase evolution mechanisms and crystal growth dynamics of cesium lead bromide halide films.

MOF-Transformed In_(2)O_(3-x)@C Nanocorn Electrocatalyst for Efficient CO_(2)Reduction to HCOOH

For electrochemical CO_(2) reduction to HCOOH,an ongoing challenge is to design energy efficient electrocatalysts that can deliver a high HCOOH current density(JHCOOH)at a low overpotential.Indium oxide is good HCOOH production catalyst but with low con-ductivity.In this work,we report a unique corn design of In_(2)O_(3-x)@C nanocatalyst,wherein In_(2)O_(3-x)nanocube as the fine grains dispersed uniformly on the carbon nanorod cob,resulting in the enhanced conductivity.Excellent performance is achieved with 84%Faradaic efficiency(FE)and 11 mA cm^(−2)JHCOOH at a low potential of−0.4 V versus RHE.At the current density of 100 mA cm^(−2),the applied potential remained stable for more than 120 h with the FE above 90%.Density functional theory calculations reveal that the abundant oxygen vacancy in In_(2)O_(3-x) has exposed more In^(3+) sites with activated electroactivity,which facilitates the formation of HCOO*intermediate.Operando X-ray absorp-tion spectroscopy also confirms In^(3+) as the active site and the key intermediate of HCOO*during the process of CO_(2) reduction to HCOOH.

Antioxidative solution processing yields exceptional Sn(Ⅱ) stability for sub-1.4 eV bandgap inorganic perovskite solar cells

Owing to the combined features of sub-1.4 eV bandgap and all-inorganic composition,cesium tin–lead(Sn-Pb)triiodide perovskite is promising for approaching the Shockley-Queisser limit of solar cells while avoiding the use of volatile organic cations.But the low Sn(Ⅱ)stability in this perovskite remains a hurdle for delivering its theoretically attainable device performance.Herein we present a synthesis method of this perovskite based on an acetylhydrazine-incorporated antioxidative solution system.Mechanistic investigation shows that acetylhydrazine effectively reduces the oxidation of solution-phase Sn(Ⅱ)and meanwhile creates an electron-rich,protective nano-environment for solid-state Sn(Ⅱ)ions.These lead to high oxidation resistance of the final film as well as effective defect inhibition.The resultant solar cells demonstrate power conversion efficiencies up to 15.04%,the highest reported so far for inorganic perovskite devices with sub-1.4 eV bandgaps.Furthermore,the T_(90) lifetime of these devices can exceed 1000 hours upon light soaking in a nitrogen atmosphere,demonstrating the potential advantage when lower-bandgap perovskite solar cells go all-inorganic.

In-situ fabrication of dual porous titanium dioxide films as anode for carbon cathode based perovskite solar cell

We develop a dual porous （DP） TiO2 film for the electron transporting layer （ETL） in carbon cathode based perovskite solar cells （C-PSCs）. The DP TiO2 film was synthesized via a facile PS-templated method with the thickness being controlled by the spin-coating speed. It was found that there is an optimum DP TiO2 film thickness for achieving an effective ETL, a suitable perovskite]TiO2 interface, an efficient light harvester and thus a high performance C-PSC. In particular, such a DP TiO2 film can act as a scaffold for complete-filling of the pores with perovskite and for forming high-quality perovskite crystals that are seamlessly interfaced with Ti02 to enhance interracial charge injection. Leveraging the unique advantages of DP TiO2 ETL, together with a dense-packed and pinhole-free TiO2 compact layer, PCE of the C-PSCs has reached 9.81% with good stability.

Long-Chain Gemini Surfactant-Assisted Blade Coating Enables Large-Area Carbon-Based Perovskite Solar Modules with Record Performance

Carbon-based perovskite solar cells show great potential owing to their low-cost production and superior stability in ambient air.However,scaling up to high-efficiency carbon-based solar modules hinges on reliable deposition of uniform defect-free perovskite films over large areas,which is an unsettled but urgent issue.In this work,a long-chain gemini surfactant is introduced into perovskite precursor ink to enforce self-assembly into a network structure,considerably enhancing the coverage and smoothness of the perovskite films.The long gemini surfactant plays a distinctively synergistic role in perovskite film construction,crystallization kinetics modulation and defect passivation,leading to a certified record power conversion efficiency of 15.46%with Voc of 1.13 V and Jsc of 22.92 mA cm^(-2)for this type of modules.Importantly,all of the functional layers of the module are printed through a simple and high-speed(300 cm min^(-1))blade coating strategy in ambient atmosphere.These results mark a significant step toward the commercialization of all-printable carbon-based perovskite solar modules.

D-π-D molecular layer electronically bridges the NiO_(x) hole transport layer and the perovskite layer towards high performance photovoltaics

Nickel oxide (NiO_(x)) has significant cost and stability advantages over poly[bis (4-phenyl)(2,4,6-trimethyl phenyl)amine](PTAA) for inverted p-i-n perovskite solar cells (PSCs),but the poor NiO_(x)/perovskite contact stemming from some reactive species at the interface led to suboptimal device performance.To solve this problem,we take a multiple donor molecule approach,using 3,3’-(4,8-bis(hexylthio)benzo[1,2-b:4,5-b’]dithiophene-2,6-diyl)bis(10-(6-bromohexyl)-10H-phenoxazine)(BDT-POZ) as an example,to modify the NiO_(x)/perovskite interface.The primary goal was to reduce the under-coordinated Ni^(≥3+) cations via electron transfer from the donor molecules to NiO_(x),thus mitigating the detrimental reactions between perovskite and NiO_(x).Equally importantly,the hole extraction at the interface was greatly enhanced after the organic donor modification,since the hydrophobic species atop NiO_(x) not only enabled pinhole-free crystallization of the perovskite but also properly tuned the interfacial energy level alignment.Consequently,the PSCs with NiO_(x)/BDT-POZ HTL achieved a high power conversion efficiency (PCE) up to 20.16%,which compared excellently with that of the non-modified devices (17.83%).This work provides a new strategy to tackle the exacting issues that have so far impeded the development of NiO_(x) based PSCs.

空间选择性缺陷管理制备高性能碳基CsPbI_(3)钙钛矿太阳能电池

Defects formed at the surface,buried interface and grain boundaries(GB)of CsPbI_(3)perovskite films considerably limit photovoltaic performance.Such defects could be passivated effectively by the most prevalent post modification strategy without compromising the photoelectric properties of perovskite films,but it is still a great challenge to make this strategy comprehensive to different defects spatially distributed throughout the films.Herein,a spatially selective defect management(SSDM)strategy is developed to roundly passivate various defects at different locations within the perovskite film by a facile one-step treatment procedure using a piperazine-1,4-diium tetrafluoroborate(PZD(BF_(4))_(2))solution.The small-size PZD^(2+)cations could penetrate into the film interior and even make it all the way to the buried interface of CsPbI_(3)perovskite films,while the BF_(4)^(-)anions,with largely different properties from I^(-)anions,mainly anchor on the film surface.Consequently,virtually all the defects at the surface,buried interface and grain boundaries of CsPbI_(3)perovskite films are effectively healed,leading to significantly improved film quality,enhanced phase stability,optimized energy level alignment and promoted carrier transport.With these films,the fabricated CsPbI_(3)PSCs based on carbon electrode(C-PSCs)achieve an efficiency of18.27%,which is among the highest-reported values for inorganic C-PSCs,and stability of 500 h at 85℃with 65%efficiency maintenance.

Filterless narrowband photodetectors enabled by controllable band modulation through ion migration: The case of halide perovskites

Narrowband photodetectors conventionally rely on optical structure design orbandpass filters to achieve the narrowband regime. Recently, a strategy forfilterless narrowband photoresponse based on the charge collection narrowing(CCN) mechanism was reported. However, the CCN strategy requires an electrically and optically “thick” photoactive layer, which poses challenges in controlling the narrowband photoresponse. Here we propose a novel strategy forconstructing narrowband photodetectors by leveraging the inherent ion migration in perovskites, which we term “band modulation narrowing” (BMN). Bymanipulating the ion migration with external stimuli such as illumination,temperature, and bias voltage, we can regulate in situ the energy-band structure of perovskite photodetectors (PPDs) and hence their spectral response.Combining the Fermi energy levels obtained by the Kelvin probe force microscopy, the internal potential profiles from solar cell capacitance simulator simulation, and the anion accumulation revealed by the transient ion-drifttechnique, we discover two critical mechanisms behind our BMN strategy: theextension of an optically active but electronically dead region proximal to the top electrode and the down-bending energy bands near the electron transportlayer. Our findings offer a case for harnessing the often-annoying ionmigration for developing advanced narrowband PPDs.

Photovoltaics of low-bandgap inorganic perovskites

Low-bandgap inorganic perovskites are a group of materials that can simultaneously harness the stability merit of an all-inorganic composition and high photovoltaic efficiency potential of low-bandgap light absorbers as compared with other perovskite materials.Therefore,low-bandgap inorganic perovskites are promising materials options for the development of both single-junction and tandem solar cells.In this review,we summarize the recent studies addressing the major issues related to these perovskites,including the low phase stability and uncontrolled Sn-related defects.We also present a perspective discussion on future research directions related to these perovskites.We propose to gain insights into those unique thermodynamic and kinetic behaviors of these perovskites to understand and overcome their low phase stability.In particular,we envision that fundamental investigations leveraging 119Sn NMR may open a new pathway for understanding and alleviating Sn-related defects.Continued efforts in the discussed areas are expected to unleash the full technological potential of low-bandgap inorganic perovskites for high-performance solar cells and modules.

Directing the photogenerated charge flow in a photocathodic metal protection system with single-domain ferroelectric PbTiO_(3)nanoplates

Photocathodic protection(PCP)is arguably an ideal alternative technology to the conventional electrochemical cathodic protection methods for corrosion mitigation of metallic infrastructure due to its eco-friendliness and low-energy-consumption,but the construction of highlyefficient PCP systems still remains challenging,caused primarily by the lack of driving force to guide the charge flow through the whole PCP photoanodes.Here,we tackle this key issue by equipping the PCP photoanode with ferroelectric single-domain PbTiO_(3)nanoplates,which can form a directional“macroscopic electric field”throughout the entire photoanode controllable by external polarization.The properly poled PCP photoanode allows the photogenerated electrons and holes to migrate in opposite directions,that is,electrons to the protected metal and holes to the photoanode/electrolyte interface,leading to largely suppressed charge annihilation and consequently a considerable boost in the overall solar energy conversion efficiency of the PCP system.The as-fabricated photoanode can not only supply sufficient photocurrent to 304 stainless steel to initiate cathodic protection,but also shift the metal potential to the corrosion-free range.Our findings provide a viable design strategy for future high-performance PCP systems based on ferroelectric nanomaterials with enhanced charge flow manipulation.

Major strategies for improving the performance of perovskite solar cells

Metal halide perovskite solar cell(PSC)has successfully distinguished itself in optoelectronic field by virtue of the sharp rise in power conversion efficiency over the past decade.The remarkable efficiency breakthrough at such a fast speed can be mainly attributed to the comprehensive study on film deposition techniques,especially the effective management of surface and interfacial defects in recent works.Herein,we summarized the current trends in performance enhancement for PSCs,with a focus on the generally applicable strategies in high-performance works,involving deposition methods,compositional engineering,additive engineering,crystallization manipulation,charge transport material selection,interfacial passivation,optical coupling effect and constructing tandem solar cells.Promising directions and perspectives are also provided.

Highly efficient and stable white LEDs based on pure red narrow bandwidth emission triangular carbon quantum dots for wide-color gamut backlight displays

High-performance white light-emitting diodes (WLEDs) hold great potential for the next-generation backlight display applications.However,achieving highly efficient and stable WLEDs with wide-color-gamut has remained a formidable goal.Reported here is the first example of pure red narrow bandwidth emission triangular CQDs (PR-NBE-T-CQDs) with photoluminescence peaking at 610 nm.The PR-NBE-T-CQDs synthesized from resorcinol show high quantum yield (QY) of 72% with small full width at half maximum of 33 nm.By simply controlling the reaction time,pure green (PG-) NBE-T-CQDs with high QY of 75% were also obtained.Highly efficient and stable WLEDs with wide-color-gamut based on PR- and PG-NBE-T-CQDs was achieved.This WLED showed a remarkable wide-color gamut of 110% NTSC and high power efficiency of 86.5 lumens per Watt.Furthermore,such WLEDs demonstrate outstanding stability.This work will set the stage for developing highly efficient,low cost and environment-friendly WLEDs based on CQDs for the next-generation wide-color gamut backlight displays.

Current progress in developing metal oxide nanoarrays-based photoanodes for photoelectrochemical water splitting

Solar energy driven photoelectrochemical(PEC) water splitting is a clean and powerful approach for renewable hydrogen production. The design and construction of metal oxide based nanoarray photoanodes is one of the promising strategies to make the continuous breakthroughs in solar to hydrogen conversion efficiency of PEC cells owing to their owned several advantages including enhanced reactive surface at the electrode/electrolyte interface, improved light absorption capability, increased charge separation efficiency and direct electron transport pathways. In this Review, we first introduce the structure,work principle and their relevant efficiency calculations of a PEC cell. We then give a summary of the state-of the-art research in the preparation strategies and growth mechanism for the metal oxide based nanoarrays, and some details about the performances of metal oxide based nanoarray photoanodes for PEC water splitting. Finally, we discuss key aspects which should be addressed in continued work on realizing high-efficiency metal oxide based nanoarray photoanodes for PEC solar water splitting systems.

Materials and structures for the electron transport layer of efficient and stable perovskite solar cells

The electron transport layer plays a vital function in extracting and transporting photogenerated electrons, modifying the interface, aligning the interfacial energy level and minimizing the charge recombination in perovskite solar cells. This review summarizes the recent research progress on electron transport materials of metal oxides, organic molecules and multilayers. The doped metal oxides as electron transport materials in regular perovskite solar cells show improved device performance relative to their non-doped counterpart due to enhanced electron mobility and energy level alignment. The non-fullerene organic electron transport materials with better electron mobility and tunable energy level alignment need to be further designed and developed despite their advantages of mechanical flexibility and wide range tunability. The multilayer electron transport materials are suggested to be an important direction of research for efficient and stable perovskite solar cells because of their favorable synergistic interaction.

High-quality perovskite in thick scaffold： a core issue for hole transport material-free perovskite solar cells

Organic-inorganic perovskite solar cells （PSCs） have attracted intense attention in the last few years due to the phenomenal increase in power conversion efficiency （PCE）, but their low stability has greatly hindered their practical application. By removing unstable hole transport materials （HTM）, the device stability of HTM-free PSCs has been greatly improved. However, the PCE has largely lagged behind those of HTM-based PSCs. We contend that deposition of high-quality perovskite into a thick scaffold is the key to achieving high-performance, HTM-free PSCs. Indeed, a few deposition methods have been used to successfully deposit a high-quality perovskite layer into a relatively thick TiO2 scaffold, hence producing PSCs with relatively high PCEs. In this review, we will introduce the basic working principle of HTM-free PSCs and analyze the important role of thick TiO2 scaffold. Most importantly, the problems of the conventional perovskite deposition methods in thick TiO2 scaffold will be examined and some recent successful deposition methods will be surveyed. Finally, we will draw conclusions and highlight some promising research directions for HTM-free PSCs.

Erratum to:Highly efficient and stable white LEDs based on pure red narrow bandwidth emission triangular carbon quantum dots for wide-color gamut backlight displays

In the version of this article originally published,Figs.2(d)and 3(a),and Figs.S3 and S6 in the Electronic Supplementary Material(ESM)were incorrect.The corrected images are shown below.

Two-step solvent post-treatment on PTAA for highly efficient and stable inverted perovskite solar cells

Modifying the surface of poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine](PTAA)with toluene during the high-speed spin-coating process of dimethylformamide considerably improves the wettability and morphology of PTAA and results in improvement of the crystallinity and absorption of perovskite film.The hole mobility and ohm contact have also been improved accordingly.Combined with these improved parameters,inverted perovskite solar cells with high efficiency of 19.13%and long-term stability could be achieved,which are much better than those with untreated PTAA.Importantly,our devices can keep 88.4%of the initial power conversion efficicncy after 30 days of storage in ambient air.

A dual plasmonic core-shell Pt/[TiN@TiO_(2)]catalyst for enhanced photothermal synergistic catalytic activity of VOCs abatement

Volatile organic compounds(VOCs)are ubiquitous organic pollutants affecting atmospheric environment and human health.The development of new efficient and environmentally friendly materials utilizing photothermal synergistic catalysis for purification of VOCs is still challenging.Herein,we design and prepare a core–shell TiN@TiO_(2)nanostructure integrating with nanoscaled Pt(Pt/[TiN@TiO_(2)])by an attractive quenching method.The strong light-harvesting capability of Pt and TiN components improve light-to-heat utilization efficiency by their intrinsic surface plasmon resonance effect.The TiO_(2)component upon the surface and the coexisting coupling effect of Pt0 and Pt2+enhance the photocatalytic effect of the system.As a result,the catalytic performance is significantly improved with toluene(120 ppm)conversion of 100%under the gas hourly space velocity of 72,000 mL·g^(−1)·h^(−1)and light illumination of 500 mW·cm^(−2).The desired catalyst thus achieves highly efficient coupling effect of photocatalysis and light-to-heat conversion for promoting VOCs abatement.

High-performance, stable and low-cost mesoscopic perovskite （CH3NH3PbI3） solar cells based on poly（3-hexylthiophene）- modified carbon nanotube cathodes

This work explores the use of poly（3- hexylthiophene） （P3HT） modified carbon nanotubes （CNTs@P3HT） for the cathodes of hole transporter free, mesoscopic perovskite （CH3NH3PbI3） solar cells （PSCs）, simultaneously achieving high-performance, high stability and low-cost PSCs. Here the thin P3HT modifier acts as an electron blocker to inhibit electron transfer into CNTs and a hydrophobic polymer binder to tightly cross-link the CNTs together to compact the carbon electrode film and greatly stabilize the solar cell. On the other hand, the presence of CNTs greatly improve the conductivity of P3HT. By optimizing the concentration of the P3HT modifier （2 mg/mL）, we have improved the power conversion efficiencies （PCEs） of CNTs@P3HT based PSCs up to 13.43% with an average efficiency of 12.54%, which is much higher than the pure CNTs based PSCs （best PCE 10.59%） and the sandwich-type P3HT/CNTs based PSCs （best PCE 9.50%）. In addition, the hysteresis of the CNTs@P3HT based PSCs is remarkably reduced due to the intimate interface between the perovskite and CNTs@P3HT electrodes. Degradation of the CNTs@ P3HT based PSCs is also strongly retarded as compared to cells employing the pure CNTs electrode when exposed to the ambient condition of 20%- 40% humidity.

Light tuning CO/H_(2)composition on Ag:Unraveling CO_(2)mass transfer and electron-phonon coupling in plasmon-enhanced electrocatalysis

Plasmon-enhanced electrocatalysis(PEEC)is an emerging approach to mitigate CO_(2)emissions.The mechanisms behind CO_(2)adsorption and reduction at the catalyst-electrolyte interface in PEEC still need to be further explored.Herein,we employ a well-defined Ag nanostructure to elucidate these pivotal issues.By shining light with wavelengths of 625,525,405 nm on Ag,an adjustable CO/H_(2)ratio from 35 to 1 can be obtained.The reaction pathway changing under plasmonic excitation does not originate from the lowered CO_(2)mass transfer in the vicinity of Ag,as the electrochemical quartz crystal microbalance results unravel that a slightly elevated temperature in bulk electrolyte caused by light irradiation cannot weaken the CO_(2)adsorption at the Ag catalyst-electrolyte interface.Theoretical calculations reveal that optical excitation towards shorter wavelengths leads to a progressive lowered energy barrier for H_(2)formation together with an enhanced energy barrier for^(*)COOH formation.Although thermodynamically suppressed,CO_(2)reduction can still be improved kinetically by optimizing the excitation wavelength and intensity,being accompanied with the enhanced photocurrent.Transient absorption spectroscopy results further correlate the higher photocurrent with a prolonged electron-phonon coupling time,verifying that the improvement of CO_(2)reduction kinetics in PEEC can be realized by hot electron harnessing.