Sol-gel-based porous Ti-doped tungsten oxide films for high-performance dual-band electrochromic smart windows

Dual-band electrochromic smart windows(DESWs)with independent control of the transmittance of near-infrared and visible light show great potential in the application of smart and energy-saving buildings.The current strategy for building DESWs is to screen materials for composite or prepare plasmonic nanocrystal films.These rigorous preparation processes seriously limit the further development of DESWs.Herein,we report a facile and effective sol-gel strategy using a foaming agent to achieve porous Ti-doped tungsten oxide film for the high performance of DESWs.The introduction of foaming agent polyvinylpyrrolidone during the film preparation can increase the specific surface area and free carrier concentration of the films and enhance their independent regulation ability of near-infrared electrochromism.As a result,the optimal film shows excellent dual-band electrochromic properties,including high optical modulation(84.9%at 633 nm and 90.3%at 1200 nm),high coloration efficiency(114.9 cm^(2) C^(-1) at 633 nm and 420.3 cm^(2) C^(-1) at 1200 nm),quick switching time,excellent bistability,and good cycle stability(the transmittance modulation losses at 633 and 1200 nm were 11%and 3.5%respectively after 1000 cycles).A demonstrated DESW fabricated by the sol-gel film showed effective management of heat and light of sunlight.This study represents a significant advance in the preparation of dual-band electrochromic films,which will shed new light on advancing electrochromic technology for future energy-saving smart buildings.

Reversible Zn^(2+) Insertion in Tungsten Ion-Activated Titanium Dioxide Nanocrystals for Electrochromic Windows

Zinc-anode-based electrochromic devices(ZECDs) are emerging as the next-generation energy-e cient transparent electronics. We report anatase W-doped TiO_(2) nanocrystals(NCs) as a Zn^(2+) active electrochromic material. It demonstrates that the W doping in TiO_(2) highly reduces the Zn^(2+) intercalation energy,thus triggering the electrochromism. The prototype ZECDs based on W-doped TiO_(2) NCs deliver a high optical modulation(66% at 550 nm),fast spectral response times(9/2.7 s at 550 nm for coloration/bleaching),and good electrochemical stability(8.2% optical modulation loss after 1000 cycles).

Advances and Challenges in Two‑Dimensional Organic–Inorganic Hybrid Perovskites Toward High‑Performance Light‑Emitting Diodes

Two-dimensional(2D)perovskites are known as one of the most promising luminescent materials due to their structural diversity and outstanding optoelectronic properties.Compared with 3D perovskites,2D perovskites have natural quantum well structures,large exciton binding energy(Eb)and outstanding thermal stability,which shows great potential in the next-generation displays and solidstate lighting.In this review,the fundamental structure,photophysical and electrical properties of 2D perovskite films were illustrated systematically.Based on the advantages of 2D perovskites,such as special energy funnel process,ultrafast energy transfer,dense film and low efficiency roll-off,the remarkable achievements of 2D perovskite light-emitting diodes(PeLEDs)are summarized,and exciting challenges of 2D perovskite are also discussed.An outlook on further improving the efficiency of pure-blue PeLEDs,enhancing the operational stability of PeLEDs and reducing the toxicity to push this field forward was also provided.This review provides an overview of the recent developments of 2D perovskite materials and LED applications,and outlining challenges for achieving the high-performance devices.

Realizing efficient emission and triple-mode photoluminescence switching in air-stable tin(IV)-based metal halides via antimony doping and rational structural modulation

Recently,many lead-free metal halides with diverse structures and highly efficient emission have been reported.However,their poor stability and single-mode emission color severely limit their applications.Herein,three homologous Sb^(3+)-doped zero-dimensional(0D)air-stable Sn(IV)-based metal halides with different crystal structures were developed by inserting a single organic ligand into SnCl_(4)lattice,which brings different optical properties.Under photoexcitation,(C_(25)H_(22)P)SnC_(l5)@Sb⋅CH_(4O)(Sb^(3+)−1)does not emit light,(C_(25)H_(22)P)_(2)SnC_(l6)@Sb-α(Sb^(3+)−2α)shines bright yellow emission with a photoluminescence quantum yield(PLQY)of 92%,and(C_(25)H_(22)P)_(2)SnC_(l6)@Sb-β(Sb^(3+)−2β)exhibits intense red emission with a PLQY of 78%.The above three compounds show quite different optical properties should be due to their different crystal structures and the lattice distortions.Particularly,Sb^(3+)−1 can be successfully converted into Sb^(3+)−2αunder the treatment of C_(25)H_(22)PCl solution,accompanied by a transition from nonemission to efficient yellow emission,serving as a“turn-on”photoluminescence(PL)switching.Parallelly,a reversible structure conversion between Sb^(3+)−2αand Sb^(3+)−2βwas witnessed after dichloromethane or volatilization treatment,accompanied by yellow and red emission switching.Thereby,a triple-mode tunable PL switching of off-onI-onII can be constructed in Sb^(3+)-doped Sn(IV)-based compounds.Finally,we demonstrated the as-synthesized compounds in fluorescent anticounterfeiting,information encryption,and optical logic gates.

Boosting triplet self-trapped exciton emission in Te(IV)-doped Cs_(2)SnCl_(6) perovskite variants

Perovskite variants have attracted wide interest because of the lead-free nature and strong self-trapped exciton (STE) emission. Divalent Sn(II) in CsSnX3 perovskites is easily oxidized to tetravalent Sn(IV), and the resulted Cs2SnCl6 vacancy-ordered perovskite variant exhibits poor photoluminescence property although it has a direct band gap. Controllable doping is an effective strategy to regulate the optical properties of Cs2SnX6. Herein, combining the first principles calculation and spectral analysis, we attempted to understand the luminescence mechanism of Te4+-doped Cs2SnCl6 lead-free perovskite variants. The chemical potential and defect formation energy are calculated to confirm theoretically the feasible substitutability of tetravalent Te4+ ions in Cs2SnCl6 lattices for the Sn-site. Through analysis of the absorption, emission/excitation, and time-resolved photoluminescence (PL) spectroscopy, the intense green-yellow emission in Te4+:Cs2SnCl6 was considered to originate from the triplet Te(IV) ion 3P1→1S0 STE recombination. Temperature-dependent PL spectra demonstrated the strong electron-phonon coupling that inducing an evident lattice distortion to produce STEs. We further calculated the electronic band structure and molecular orbital levels to reveal the underlying photophysical process. These results will shed light on the doping modulated luminescence properties in stable lead-free Cs2MX6 vacancy-ordered perovskite variants and be helpful to understand the optical properties and physical processes of doped perovskite variants.

Highly efficient green InP-based quantum dot light-emitting diodes regulated by inner alloyed shell component

InP-based quantum dot light-emitting diodes(QLEDs),as less toxic than Cd-free and Pb-free optoelectronic devices,have become the most promising benign alternatives for the next generation lighting and display.However,the development of green-emitting InP-based QLEDs still remains a great challenge to the environmental preparation of InP quantum dots(QDs)and superior device performance.Herein,we reported the highly efficient green-emitting InP-based QLEDs regulated by the inner alloyed shell components.Based on the environmental phosphorus tris(dimethylamino)phosphine((DMA)3P),we obtained highly efficient InP-based QDs with the narrowest full width at half maximum(~35 nm)and highest quantum yield(~97%)by inserting the gradient inner shell layer ZnSe_(x)S_(1-x)without further post-treatment.More importantly,we concretely discussed the effect and physical mechanism of ZnSe_(x)S_(1-x)layer on the performance of QDs and QLEDs through the characterization of structure,luminescence,femtosecond transient absorption,and ultraviolet photoelectron spectroscopy.We demonstrated that the insert inner alloyed shell ZnSe_(x)S_(1-x)provided bifunctionality,which diminished the interface defects upon balancing the lattice mismatch and tailored the energy levels of InP-based QDs which could promote the balanced carrier injection.The resulting QLEDs applying the InP/ZnSe_(0.7)S_(0.3)/ZnS QDs as an emitter layer exhibited a maximum external quantum efficiency of 15.2%with the electroluminescence peak of 532 nm,which was almost the highest record of InP-based pure green-emitting QLEDs.These results demonstrated the applicability and processability of inner shell component engineering in the preparation of high-quallity InP-based QLEDs.

On the accurate characterization of quantum-dot light-emitting diodes for display applications

Quantum dot light-emitting diodes(QLEDs)are a class of high-performance solution-processed electroluminescent(EL)devices highly attractive for next-generation display applications.Despite the encouraging advances in the mechanism investigation,material chemistry,and device engineering of QLEDs,the lack of standard protocols for the characterization of QLEDs may cause inaccurate measurements of device parameters and invalid comparison of different devices.Here,we report a comprehensive study on the characterizations of QLEDs using various methods.We show that the emission non-uniformity across the active area,nonLambertian angular distributions of EL intensity,and discrepancies in the adopted spectral luminous efficiency functions could introduce significant errors in the device efficiency.Larger errors in the operational-lifetime measurements may arise from the inaccurate determination of the initial luminance and inconsistent methods for analyzing the luminance-decay curves.Finally,we suggest a set of recommended practices and a checklist for device characterizations,aiming to help the researchers in the QLED field to achieve accurate and reliable measurements.

Boosting electroluminescence performance of all solution processed In P based quantum dot light emitting diodes using bilayered inorganic hole injection layers

The development of high-performance In P-based quantum dot light-emitting diodes(QLEDs)has become the current trend in ecofriendly display and lighting technology.However,compared with Cd-based QLEDs that have already been devoted to industry,the efficiency and stability of In P-based QLEDs still face great challenges.In this work,colloidal Ni Oxand Mg-doped Ni Oxnanocrystals were used to prepare a bilayered hole injection layer(HIL)to replace the classical polystyrene sulfonate(PEDOT:PSS)HIL to construct high-performance In Pbased QLEDs.Compared with QLEDs with a single HIL of PEDOT:PSS,the bilayered HIL enables the external quantum efficiencies of the QLEDs to increase from 7.6%to 11.2%,and the T_(95)lifetime(time that the device brightness decreases to 95%of its initial value)under a high brightness of 1000 cd m^(-2)to prolong about 7 times.The improved performance of QLEDs is attributed to the bilayered HIL reducing the mismatched potential barrier of hole injection,narrows the potential barrier difference of indium tin oxide(ITO)/hole transport layer interface to promote carrier balance injection,and realizes high-efficiency radiative recombination.The experimental results indicate that the use of bilayered HILs with p-type Ni Oxmight be an efficient method for fabricating high-performance In P-based QLEDs.

Unraveling the Effect of Cation Types on Electrochromic Properties of Titanium Dioxide Nanocrystals

Electrochromic(EC)devices have been regarded as promising candidates for energy-saving smart windows,next-generation displays,and wearable electronics.Monovalent ions such as H^(+)-and Li^(+)-based electrolytes are the benchmark insertion ions for EC devices but have serious limitations such as high cost,instability,and difficulty to handle.Seeking multivalent electrolytes is an effective alternative way to prepare high-performance EC devices;unfortunately,the related reports are currently limited to tungsten oxide EC materials.Herein,for the first time,we investigate the EC properties driven by different valence cationic(i.e.,Li^(+),Zn^(2+),and Al^(3+))electrolytes in the titanium dioxide system.It is found that the initial optical modulation ranges of TiO_(2)nanocrystal(NC)films in Li^(+),Zn^(2+),and Al^(3+)electrolytes are 76.8%,77.4%,and 77.3%,respectively.After 250 cycles,the optical contrast of these films in Zn^(2+)electrolyte decreased by only 2.3%,much lower than that in benchmark Li^(+)electrolyte of 10.1%and Al^(3+)electrolyte of 59.1%.Density functional theory calculation indicates that the potential barriers of Li^(+),Zn^(2+),and Al^(3+)in TiO_(2)are 0.59,0.55,and 0.74 eV,respectively,which makes TiO_(2)NCs show good EC properties in Zn^(2+)electrolytes.This work unravels the effect of different valence cations on the electrochromic properties of titanium dioxide NCs,which may provide some new directions for the development of excellent EC devices with long-term stability and durability.