Showing papers by "Zhen Li published in 2018"
TL;DR: In this paper, the authors review recent progress and challenges in scaling up perovskite solar cells and related efforts to enable the terawatt-scale manufacturing and deployment of this PV technology.
Abstract: Perovskite materials use earth-abundant elements, have low formation energies for deposition and are compatible with roll-to-roll and other high-volume manufacturing techniques. These features make perovskite solar cells (PSCs) suitable for terawatt-scale energy production with low production costs and low capital expenditure. Demonstrations of performance comparable to that of other thin-film photovoltaics (PVs) and improvements in laboratory-scale cell stability have recently made scale up of this PV technology an intense area of research focus. Here, we review recent progress and challenges in scaling up PSCs and related efforts to enable the terawatt-scale manufacturing and deployment of this PV technology. We discuss common device and module architectures, scalable deposition methods and progress in the scalable deposition of perovskite and charge-transport layers. We also provide an overview of device and module stability, module-level characterization techniques and techno-economic analyses of perovskite PV modules. Perovskite solar cells (PSCs) have emerged as a revolutionary class of photovoltaic technology. Here, we review recent progress and challenges in scaling up PSCs towards commercialization. We discuss several areas, including device architectures, deposition methods, scalable deposition of perovskite and charge transport layers, device stability, module-level characterization and techno-economic analyses.
679 citations
TL;DR: It is found that strong π–π interactions in solid state can promote the persistent RTP and CS-CF3 shows the unique photo-induced phosphorescence in response to the changes in molecular packing, further confirming the key influence of the molecular packing on the RTP property.
Abstract: Organic luminogens with persistent room temperature phosphorescence (RTP) have attracted great attention for their wide applications in optoelectronic devices and bioimaging. However, these materials are still very scarce, partially due to the unclear mechanism and lack of designing guidelines. Herein we develop seven 10-phenyl-10H-phenothiazine-5,5-dioxide-based derivatives, reveal their different RTP properties and underlying mechanism, and exploit their potential imaging applications. Coupled with the preliminary theoretical calculations, it is found that strong π-π interactions in solid state can promote the persistent RTP. Particularly, CS-CF3 shows the unique photo-induced phosphorescence in response to the changes in molecular packing, further confirming the key influence of the molecular packing on the RTP property. Furthermore, CS-F with its long RTP lifetime could be utilized for real-time excitation-free phosphorescent imaging in living mice. Thus, our study paves the way for the development of persistent RTP materials, in both the practical applications and the inherent mechanism.
645 citations
TL;DR: In this article, carbon quantum dots (CQDs) implanted in the surface plane of graphite carbon nitride (g-C3 N4 ) nanotubes were synthesized by thermal polymerization of freeze-dried urea and CQDs precursor.
Abstract: Graphite carbon nitride (g-C3 N4 ) is a promising candidate for photocatalytic hydrogen production, but only shows moderate activity owing to sluggish photocarrier transfer and insufficient light absorption. Herein, carbon quantum dots (CQDs) implanted in the surface plane of g-C3 N4 nanotubes were synthesized by thermal polymerization of freeze-dried urea and CQDs precursor. The CQD-implanted g-C3 N4 nanotubes (CCTs) could simultaneously facilitate photoelectron transport and suppress charge recombination through their specially coupled heterogeneous interface. The electronic structure and morphology were optimized in the CCTs, contributing to greater visible light absorption and a weakened barrier of the photocarrier transfer. As a result, the CCTs exhibited efficient photocatalytic performance under light irradiation with a high H2 production rate of 3538.3 μmol g-1 h-1 and a notable quantum yield of 10.94 % at 420 nm.
381 citations
TL;DR: The 10Ni2P@CdS catalyst as mentioned in this paper improved the anti-photocorrosion resistance of CdS by coating Ni2P shell and assembling an artificial gill to remove newly formed O2 from water.
Abstract: CdS photocorrosion seriously impeded its application in photocatalysis, especially for water splitting. Here we report new strategies to improve CdS photocorrosion resistance properties significantly by coating Ni2P shell and assembling an artificial gill to remove newly formed O2 from water. Ni2P@CdS catalyst can achieve the over-all water splitting under visible light irradiation without addition of any sacrifice reagent and noble metal loading. Compared with CdS itself, the 10Ni2P@CdS photocatalyst exhibits excellent photocatalytic activity for hydrogen evolution (251.4 μmol of H2 in 180 min) with a high AQE (3.89% at 430 nm). This catalyst also presents high photocurrent, low overpotential (−0.32 V vs SCE), and long fluorescence lifetime (16.27 ns) of excited charges. Cd2+ ions concentration measured by ICP and long term stability results verified the anti-photocorrosion role of Ni2P shell on CdS during water splitting reaction. The activity and stability of 10Ni2P@CdS is even superior to typical 1Pt@CdS catalyst. Our results confirm CdS can be an active catalyst for photocatalytic hydrogen generation from water under visible irradiation if its stability is enhanced by protection of anti-photocorrosion over-coating shell and removing the nascent formed oxygen from water.
343 citations
TL;DR: In this article, the authors investigated the cooperation of a Lewis base and a Lewis acid by combining commercial bis-PCBM mixed isomers as the Lewis acid in the antisolvent and N-(4-bromophenyl)thiourea (BrPh-ThR) as the solver in the perovskite solution precursor.
Abstract: Achieving long-term operational stability at a high efficiency level for perovskite solar cells is the most challenging issue toward commercialization of this emerging photovoltaic technology. Here, we investigated the cooperation of a Lewis base and a Lewis acid by combining commercial bis-PCBM mixed isomers as the Lewis acid in the antisolvent and N-(4-bromophenyl)thiourea (BrPh-ThR) as the Lewis base in the perovskite solution precursor. The combination of the Lewis base and the Lewis acid synergistically passivates Pb2+ and PbX3− antisite defects, enlarges the perovskite grain size, and improves charge-carrier separation and transport, leading to improved device efficiency from 19.3% to 21.7%. In addition, this Lewis base and acid combination also suppresses moisture incursion and passivates pinholes generated in the hole-transporting layer. The unsealed devices remained at 93% of the initial efficiency value in ambient air (10–20% relative humidity) after 3600 h at 20–25 °C and dropped by 10% after 1500 h under continuous operation at 1-sun illumination and 55 °C in nitrogen with maximum power-point tracking.
232 citations
TL;DR: The S@Ni/Fe LDH cathode has successfully solved the main issues related to sulfur electrodes, and it exhibits significantly improved electrochemical performances with prolonged life over 1000 cycles and excellent rate properties.
Abstract: We have designed and synthesized novel hollow Ni/Fe layered double hydroxide (LDH) polyhedrons as an advanced sulfur host for enhancing the performance of lithium-sulfur (Li-S) batteries. The Ni/Fe LDH host shows multiple advantages. First, the Ni/Fe LDH shells can provide sufficient sulfiphilic sites for chemically bonding with polysulfides. Second, the hollow architecture can provide sufficient inner space for both loading a large amount of sulfur and accommodating its large volumetric expansion. Moreover, once the active material is confined within the host, the shells could easily restrict the outward diffusion of polysulfides, guaranteeing prolonged cycle life even with high sulfur loading. As a result, the S@Ni/Fe LDH cathode has successfully solved the main issues related to sulfur electrodes, and it exhibits significantly improved electrochemical performances with prolonged life over 1000 cycles and excellent rate properties.
225 citations
TL;DR: A self-floating sturdy polymer foam which by itself enables efficient solar steam generation without optical concentration.
Abstract: Efficient and cost-effective solar steam generation requires self-floating evaporators which can convert light into heat, prevent unnecessary heat loss and greatly accelerate evaporation without solar concentrators. Currently, the most efficient evaporators (efficiency of ∼80% under 1 sun) are invariably built from inorganic materials, which are difficult to mold into monolithic sheets. Here, we present a new polymer which can be easily solution processed into a self-floating monolithic foam. The single-component foam can be used as an evaporator with an efficiency at 1 sun comparable to that of the best graphene-based evaporators. Even at 0.5 sun, the efficiency can reach 80%. Moreover, the foam is mechanically strong, thermally stable to 300 °C and chemically resistant to organic solvents.
212 citations
TL;DR: A pyrolyzed polyacrylonitrile/selenium disulfide composite cathode with dramatically enhanced active material content and superior performances for both lithium and sodium storage is reported.
Abstract: As a special class of cathode materials for lithium-sulfur batteries, pyrolyzed polyacrylonitrile/sulfur (pPAN/S) can completely solve the polysulfide dissolution problem and deliver reliable performance. However, the applicable S contents of pPAN/S are usually lower than 50 weight % (wt %), and their capacity utilizations are not sufficient, both of which greatly limit their energy densities for commercial applications. We report a pyrolyzed polyacrylonitrile/selenium disulfide (pPAN/SeS 2 ) composite with dramatically enhanced active material content (63 wt %) and superior performances for both lithium and sodium storage. As a result, pPAN/SeS 2 delivers high capacity of >1100 mAh g −1 at 0.2 A g −1 for Li storage with extremely stable cycle life over 2000 cycles at 4.0 A g −1 . Moreover, when applied in a room temperature Na-SeS 2 battery, pPAN/SeS 2 achieves superior capacity of >900 mAh g −1 at 0.1 A g −1 and delivers prolonged cycle life over 400 cycles at 1.0 A g −1 .
210 citations
TL;DR: In this paper, a modular strategy is used to decorate isolated cobalt sites into a multichannel carbon matrix (Co@MCM) with Co content of about 1.4 wt% for efficient electrochemical reduction of oxygen.
Abstract: Single-atom catalysts (SACs) with their unique electronic and geometric structures usually exhibit extraordinary catalytic performance for many important chemical reactions. Herein, a modular strategy is used to decorate isolated cobalt sites into a multichannel carbon matrix (Co@MCM) with Co content of about 1.4 wt% for efficient electrochemical reduction of oxygen. As confirmed by X-ray absorption fine structure investigation, the pre-designed CoN4 configuration and geometric structure are well maintained in the newly developed Co@MCM. The decorated CoN4 units together with the multichannel carbon substrate with high conductivity and porosity endow the catalyst with excellent activity for the oxygen reduction reaction (ORR). Our findings not only present some fundamental insights for the accurate modulation of nanostructured catalysts at the atomic scale, but also reveal the structural origin of the enhanced catalytic activity.
207 citations
TL;DR: The microwave-assisted heating strategy may stand out as an extremely simple route to incorporating π-electron-rich barbituric acid with melamine into g-C3 N4 with markedly improved photocatalytic performance.
Abstract: A rapid and highly efficient strategy for introducing C into g-C3 N4 involves copolymerizing π-electron-rich barbituric acid with melamine via a facile microwave-assisted heating, thereby eliminating the issues in conventional electric furnace heating, such as the severe volatilization, owing to the mismatch of the sublimation temperatures of barbituric acid and melamine. The g-C3 N4 catalyst after optimizing the C-doping content actively generates increased amounts of H2 under visible light exposure with the highest H2 generation rate of 25.0 μmol h-1 , which is nearly 20 times above that using g-C3 N4 produced by conventional electric furnace heating of two identical monomers (1.3 μmol h-1 ). As such, the microwave-assisted heating strategy may stand out as an extremely simple route to incorporating π-electrons into g-C3 N4 with markedly improved photocatalytic performance.
206 citations
TL;DR: In this Review, the recent progress in understanding these organic compounds or polymers for fluorescence and phosphorescence is briefly summarized, with the aim of exploring the intrinsic principle of these novel photoluminescence systems and providing reasonable constructs for molecular design.
Abstract: Following the development of photoluminescence systems with various compositions, some nontraditional structures, including nonaromatic organic systems as fluorophores and organic luminogens as the source of phosphorescence emission at room temperature, have attracted considerable attention for their advantages in biological and medical applications, and for the updated photophysical understandings in science. In this Review, the recent progress in understanding these organic compounds or polymers for fluorescence and phosphorescence is briefly summarized, with the aim of exploring the intrinsic principle of these novel photoluminescence systems and providing reasonable constructs for molecular design. Finally, some prospects are suggested for further development of this continually expanding area of research, with the coined concept of Molecular Uniting Set Identified Characteristic (MUSIC).
TL;DR: The research history, observed phenomena, proposed possible mechanisms, different types of triboluminescent compounds, and potential applications in an attempt to find the inherent clues hidden in the scattered literature are presented.
TL;DR: A binder-free electrode based on necklace-like structures composed of Fe3 N@C yolk-shell particles as an advanced anode for Na-ion batteries is reported, which delivers a prolonged cycle life over 300 cycles, and achieves a high C-rate capacity.
Abstract: It is of great importance to develop cost-effective electrode materials for large-scale use of Na-ion batteries. Here, a binder-free electrode based on necklace-like structures composed of Fe3 N@C yolk-shell particles as an advanced anode for Na-ion batteries is reported. In this electrode, every Fe3 N@C unit has a novel yolk-shell structure, which can accommodate the volumetric changes of Fe3 N during the (de)sodiation processes for superior structural integrity. Moreover, all reaction units are threaded along the carbon fibers, guaranteeing excellent kinetics for the electrochemical reactions. As a result, when evaluated as an anode material for Na-ion batteries, the Fe3 N@C nano-necklace electrode delivers a prolonged cycle life over 300 cycles, and achieves a high C-rate capacity of 248 mAh g-1 at 2 A g-1 .
TL;DR: Analysis of the experimental results show that the molecular conformation transition of the phenothiazine group from quasi-axial to quasi-equatorial is responsible for this dynamic mechanoluminescence effect.
Abstract: A phenothiazine derivative of FCO-CzS with changeable mechanoluminescence is reported, which, upon continuous mechanical stimulus, shows mechanoluminescent emission from blue to white and yellow. Careful analysis of the experimental results, coupled with the well-understood photoluminescence theory, show that the molecular conformation transition of the phenothiazine group from quasi-axial to quasi-equatorial is responsible for this dynamic mechanoluminescence effect.
TL;DR: An overview of the current research and perspective regarding PSC technology toward future large-scale manufacturing and deployment are provided and several key challenges discussed.
TL;DR: In this paper, a spray coating of a TiO2 electron transport layer (ETL) and blade coating of both a perovskite absorber layer and a spiro-OMeTAD-based hole transport layer was used to reduce the interferences between subcells.
Abstract: To push perovskite solar cell (PSC) technology toward practical applications, large-area perovskite solar modules with multiple subcells need to be developed by fully scalable deposition approaches. Here, we demonstrate a deposition scheme for perovskite module fabrication with spray coating of a TiO2 electron transport layer (ETL) and blade coating of both a perovskite absorber layer and a spiro-OMeTAD-based hole transport layer (HTL). The TiO2 ETL remaining in the interconnection between subcells significantly affects the module performance. Reducing the TiO2 thickness changes the interconnection contact from a Schottky diode to ohmic behavior. Owing to interconnection resistance reduction, the perovskite modules with a 10 nm TiO2 layer show enhanced performance mainly associated with an improved fill factor. Finally, we demonstrate a four-cell MA0.7FA0.3PbI3 perovskite module with a stabilized power conversion efficiency (PCE) of 15.6% measured from an aperture area of ∼10.36 cm2, corresponding to an a...
TL;DR: In this article, the authors reported an example of a pure non-aromatic organic small molecule, cyanoacetic acid, that shows unexpected persistent RTP behavior with RTP lifetime as long as 862 ms.
Abstract: Efficient pure organic room temperature phosphorescence (RTP) materials have drawn considerable attention So far, most pure organic RTP molecules are aromatic compounds, and nonconjugated molecules are really scarce The only few reported non-aromatic organic phosphorescence materials are polymers without confirmed subtle structures, and there are no reports concerning non-aromatic organic small molecules with persistent RTP Here, we report an example of a pure non-aromatic organic small molecule, cyanoacetic acid, that shows unexpected persistent RTP behavior with RTP lifetime as long as 862 ms According to the CAA crystal and theoretical calculations, the presence of strong intermolecular hydrogen bonds is the key factor for its persistent RTP effect This discovery demonstrates a clear relationship between the molecular structure, packing mode and RTP effect in the non-aromatic system, which will largely extend the current pure organic RTP systems to deeply investigate the origin of light emission
TL;DR: The light-controlled exchange reaction between allyl sulfide groups allows flexible processing of tubular soft robots/actuators, which does not need any assisting materials and can be programmed into the same tube without the routine assembly of multiple tubes as used in the past.
Abstract: Stimuli-responsive materials offer a distinguished platform to build tether-free compact soft robots, which can combine sensing and actuation without a linked power supply. In the past, tubular soft robots have to be made by multiple components with various internal channels or complex cavities assembled together. Moreover, robust processing, complex locomotion, simple structure, and easy recyclability represent major challenges in this area. Here, it is shown that those challenges can be tackled by liquid crystalline elastomers with allyl sulfide functional groups. The light-controlled exchange reaction between allyl sulfide groups allows flexible processing of tubular soft robots/actuators, which does not need any assisting materials. Complex locomotion demonstrated here includes reversible simultaneous bending and elongation; reversible diameter expansion; and omnidirectional bending via remote infrared light control. Different modes of actuation can be programmed into the same tube without the routine assembly of multiple tubes as used in the past. In addition, the exchange reaction also makes it possible to use the same single tube repeatedly to perform different functions by erasing and reprogramming.
TL;DR: In this paper, the authors reported the charge carrier recombination rate and spin coherence lifetime in single crystals of two-dimensional Ruddlesden-Popper perovskites PEA2PbI4·(MAPbI3)n−1.
Abstract: We report the charge carrier recombination rate and spin coherence lifetimes in single crystals of two-dimensional (2D) Ruddlesden–Popper perovskites PEA2PbI4·(MAPbI3)n−1 (PEA, phenethylammonium; MA, methylammonium; n = 1, 2, 3, 4). Layer thickness-dependent charge carrier recombination rates are observed, with the fastest rates for n = 1 because of the large exciton binding energy, and the slowest rates are observed for n = 2. Room-temperature spin coherence times also show a nonmonotonic layer thickness dependence with an increasing spin coherence lifetime with increasing layer thickness from n = 1 to n = 4, followed by a decrease in lifetime from n = 4 to ∞. The longest coherence lifetime of ∼7 ps is observed in the n = 4 sample. Our results are consistent with two contributions: Rashba splitting increases the spin coherence lifetime going from the n = ∞ to the layered systems, while phonon scattering, which increases for smaller layers, decreases the spin coherence lifetime. The interplay between thes...
TL;DR: Four bromine-substituted fluorene-based derivatives are presented and BrFlu-CBr, having fluorescence-phosphorescence dual-emission induced not only by UV light but also by mechanical stimulus, manifests the highest phosphorescence efficiency upon photoirradiation.
Abstract: Organic tribophosphorescence materials are rarely reported and the introduction of Br atoms may be a practical way to design such materials. Here four bromine-substituted fluorene-based derivatives are presented and BrFlu-CBr, having fluorescence-phosphorescence dual-emission induced not only by UV light but also by mechanical stimulus, manifests the highest phosphorescence efficiency of 4.56 % upon photoirradiation. During the grinding process, three different triboluminescent spectra were identified. Upon introduction of a mechanical stimulus, the triboluminescence emission is cyan, whereas after an extended period it changed to blue. After removing the mechanical stimulus, green-white phosphorescent emission was observed. Careful research on single-crystal structures and theoretical calculations demonstrate that strong Br⋅⋅⋅Br interactions are vital to facilitate spin-orbit coupling and promote intersystem crossing, thus generating the unique properties.
TL;DR: Dual-modal photoacoustic imaging and single-photon-emission computed tomography imaging based on ultrasmall Cu2- xSe nanoparticles were used to noninvasively monitor the opening and recovery of the blood-brain barrier induced by focused ultrasound in living mice and indicate that the accumulated Cu 2- x Se nanoparticles could be excreted from the brain and other major organs after 15 days without causing side effects.
Abstract: The reversible and controllable opening and recovery of the blood–brain barrier (BBB) is crucial for the treatment of brain diseases, and it is a big challenge to noninvasively monitor these processes. In this article, dual-modal photoacoustic imaging and single-photon-emission computed tomography imaging based on ultrasmall Cu2–xSe nanoparticles (3.0 nm) were used to noninvasively monitor the opening and recovery of the BBB induced by focused ultrasound in living mice. The ultrasmall Cu2–xSe nanoparticles were modified with poly(ethylene glycol) to exhibit a long blood circulation time. Both small size and long blood circulation time enable them to efficiently penetrate into the brain with the assistance of ultrasound, which resulted in a strong signal at the sonicated site and allowed for photoacoustic and single-photon emission computed tomography imaging monitoring the recovery of the opened BBB. The results of biodistribution, blood routine examination, and histological staining indicate that the acc...
TL;DR: The working principle and structural design of specific AIEgen-based bioprobes that are triggered by enzymes are summarized and their great potential in biomedical applications are discussed, with the aim to promote the future research of fluorescent biop robes involving enzymes.
Abstract: Enzymes play an indispensable role in maintaining normal life activities. The abnormalities of content and activity in specific enzymes are usually associated with the occurrence and the developmen...
TL;DR: In this article, a dualmode colorimetric/fluorescence pH sensor was fabricated from carbon dots (CDs) and it exhibited a pH response via both fluorescence and visible colourimetric observation.
Abstract: A dual-mode colorimetric/fluorescence pH sensor was fabricated from carbon dots (CDs). It exhibited a pH response via both fluorescence and visible colorimetric observation. The CDs solution changed from red to yellow when the pH changed from acid to alkaline. Meanwhile, the color of pH test paper that incorporated the CDs changed from purple-red to orange and then to yellow. The CD fluorescence maximum was at 630 nm in acid solution and 590 nm under neutral and alkaline conditions. The fluorescence of the pH test paper changed from red to orange and then to yellow, which was better than that of the pure CDs solution. The CDs exhibited highly selective and reversible fluorescence quenching with respect to Cu2+ ions because of strong binding and fast chelating kinetics. There was a linear relationship between fluorescence quenching and Cu2+ concentration, suggesting the other promising practical usage of this sensing system. The versatile CDs-based pH sensor thus provides a basis for developing sustainable...
TL;DR: The tunable fluorescence of perylene diimide (PDI) derivatives was achieved by the incorporation of varied isolation groups linked on the PDI core by the result of the efficient inhibition of π-π stacking by the larger isolation groups.
Abstract: The development of fluorogens with deep-red emission is one of the hottest topics of investigation in the field of bio/chemosensors and bioimaging. Herein, the tunable fluorescence of perylene diimide (PDI) derivatives was achieved by the incorporation of varied isolation groups linked on the PDI core. With the enlarged sizes of isolation groups, the conversion from aggregation caused quenching to aggregation-induced emission was obtained in their fluorescence variations from solutions to nanoparticles, as the result of the efficient inhibition of π–π stacking by the larger isolation groups. Accordingly, DCzPDI bearing 1,3-di(9H-carbazol-9-yl)benzene as the biggest isolation group exhibited the bright deep-red emission in the aggregated state with a quantum yield of 12.3%. Combined with the three-photon excited fluorescence microscopy (3PFM) technology, through-skull 3PFM imaging of mouse cerebral vasculature can be realized by DCzPDI nanoparticles with good biocompatibility, and the penetration depth can...
TL;DR: The results indicate that the target-modulated sensitization is a useful new strategy to build UC nanoprobes and can reasonably expect that the breakthrough of SBR limit will make UC nanoprobe a more powerful tool in future studies.
Abstract: Although lanthanide-doped upconversion nanoparticles (UCNPs) have shown great promise in biosensing and bioimaging owing to their excellent photophysical properties, researchers are facing a bottle...
TL;DR: These bright NIR nanocrystals modified with 1,2-distearoyl-sn-glycero-3-phosphoethanolamine-N-[methoxy(polyethylene glycol)-2000] to endow with excellent water-solubility, biocompatibility and a blood circulation half-life of 5.9 h have great potential in NIR II imaging of tumor.
TL;DR: In this paper, a novel AIE-active ratiometric fluorescent probes for Hg2+ were synthesized, which combined the advantages of the excellent luminescence properties of AIEgens in the solid state and the high selectivity of the Hg 2+-promoted deprotection reaction.
Abstract: Novel AIE-active ratiometric fluorescent probes for Hg2+ were synthesized, which combined the advantages of the excellent luminescence properties of AIEgens in the solid state and the high selectivity of the Hg2+-promoted deprotection reaction. Upon testing with mercury ions, the luminescent color changed from sky blue to yellow-green almost immediately, while other metal ions (Ag+, Fe3+, Cu2+, Pb2+, Co2+, Cr3+, Al3+, Cd2+, Mg2+, Mn2+, Ba2+, Fe2+, Ca2+, Ni2+, Zn2+, Li+, K+, and Na+) caused no disturbance to the sensing process. Furthermore, the fabricated test strips reported the presence of Hg2+ ions with the detection limit as low as 1 × 10−5 M. Moreover, the synthesized AIEgens showed reversible mechanochromic properties with high color contrast, suggesting that they could have additional promising applications in optoelectronic devices.