Slow‐Photon‐Effect‐Induced Photoelectrical‐Conversion Efficiency Enhancement for Carbon‐Quantum‐Dot‐Sensitized Inorganic CsPbBr3 Inverse Opal Perovskite Solar Cells

All‐inorganic cesium lead halide perovskite is suggested as a promising candidate for perovskite solar cells due to its prominent thermal stability and comparable light absorption ability. Designing textured perovskite films rather than using planar‐architectural perovskites can indeed optimize the optical and photoelectrical conversion performance of perovskite photovoltaics. Herein, for the first time, this study demonstrates a rational strategy for fabricating carbon quantum dot (CQD‐) sensitized all‐inorganic CsPbBr₃ perovskite inverse opal (IO) films via a template‐assisted, spin‐coating method. CsPbBr₃ IO introduces slow‐photon effect from tunable photonic band gaps, displaying novel optical response property visible to naked eyes, while CQD inlaid among the IO frameworks not only broadens the light absorption range but also improves the charge transfer process. Applied in the perovskite solar cells, compared with planar CsPbBr₃, slow‐photon effect of CsPbBr₃ IO greatly enhances the light utilization, while CQD effectively facilitates the electron–hole extraction and injection process, prolongs the carrier lifetime, jointly contributing to a double‐boosted power conversion efficiency (PCE) of 8.29% and an increased incident photon‐to‐electron conversion efficiency of up to 76.9%. The present strategy on CsPbBr₃ IO to enhance perovskite PCE can be extended to rationally design other novel optoelectronic devices.     

A New Strategy for Humidity Independent Oxide Chemiresistors: Dynamic Self‐Refreshing of In2O3 Sensing Surface Assisted by Layer‐by‐Layer Coated CeO2 Nanoclusters

The humidity dependence of the gas sensing characteristics of metal oxide semiconductors has been one of the greatest obstacles for gas sensor applications during the last five decades because ambient humidity dynamically changes with the environmental conditions. Herein, a new and novel strategy is reported to eliminate the humidity dependence of the gas sensing characteristics of oxide chemiresistors via dynamic self‐refreshing of the sensing surface affected by water vapor chemisorption. The sensor resistance and gas response of pure In₂O₃ hollow spheres significantly change and deteriorate in humid atmospheres. In contrast, the humidity dependence becomes negligible when an optimal concentration of CeO₂ nanoclusters is uniformly loaded onto In₂O₃ hollow spheres via layer‐by‐layer (LBL) assembly. Moreover, In₂O₃ sensors LBL‐coated with CeO₂ nanoclusters show fast response/recovery, low detection limit (500 ppb), and high selectivity to acetone even in highly humid conditions (relative humidity 80%). The mechanism underlying the dynamic refreshing of the In₂O₃ sensing surfaces regardless of humidity variation is investigated in relation to the role of CeO₂ and the chemical interaction among CeO₂, In₂O₃, and water vapor. This strategy can be widely used to design high performance gas sensors including disease diagnosis via breath analysis and pollutant monitoring.     

Atomic‐Layer Deposition‐Assisted Double‐Side Interfacial Engineering for High‐Performance Flexible and Stable CsPbBr3 Perovskite Photodetectors toward Visible Light Communication Applications

Self‐powered photodetectors (PDs) based on inorganic metal halide perovskites are regarded as promising alternatives for the next generation of photodetectors. However, uncontrollable film growth and sluggish charge extraction at interfaces directly limit the sensitivity and response speed of perovskite‐based photodetectors. Herein, by assistance of an atomic layer deposition (ALD) technique, CsPbBr₃ perovskite thin films with preferred orientation and enlarged grain size are obtained on predeposited interfacial modification layers. Thanks to improved film quality and double side interfacial engineering, the optimized CsPbBr₃ (Al₂O₃/CsPbBr₃/TiO₂, ACT) perovskite PDs exhibit outstanding performance with ultralow dark current of 10^?11 A, high detectivity of 1.88 × 10¹³ Jones and broad linear dynamic range (LDR) of 172.7 dB. Significantly, excellent long‐term environmental stability (ambient conditions >100 d) and flexibility stability (>3000 cycles) are also achieved. The remarkable performance is credited to the synergistic effects of high carrier conductivity and collection efficiency, which is assisted by ALD modification layers. Finally, the ACT PDs are successfully integrated into a visible light communication system as a light receiver on transmitting texts, showing a bit rate as high as 100 kbps. These results open the window of high performance all‐inorganic halide perovskite photodetectors and extends to rational applications for optical communication.     

Reversible,Fast, and Wide‐Range Oxygen Sensor Based on Nanostructured Organometal Halide Perovskite

Nanostructured materials characterized by high surface–volume ratio hold the promise to constitute the active materials for next‐generation sensors. Solution‐processed hybrid organohalide perovskites, which have been extensively used in the last few years for optoelectronic applications, are characterized by a self‐assembled nanostructured morphology, which makes them an ideal candidate for gas sensing. Hitherto, detailed studies of the dependence of their electrical characteristics on the environmental atmosphere have not been performed, and even the effect of a ubiquitous gas such as O₂ has been widely overlooked. Here, the electrical response of organohalide perovskites to oxygen is studied. Surprisingly, a colossal increase (3000‐fold) in the resistance of perovskite‐based lateral devices is found when measured in a full oxygen atmosphere, which is ascribed to a trap healing mechanism originating from an O₂‐mediated iodine vacancies filling. A variation as small as 70 ppm in the oxygen concentration can be detected. The effect is fast (<400 ms) and fully reversible, making organohalide perovskites ideal active materials for oxygen sensing. The effect of oxygen on the electrical characteristics of organohalide perovskites must be taken into deep consideration for the design and optimization of any other perovskite‐based (opto‐) electronic device working in ambient conditions.     

DNA‐Assembled Core‐Satellite Upconverting‐Metal–Organic Framework Nanoparticle Superstructures for Efficient Photodynamic Therapy

DNA‐mediated assembly of core–satellite structures composed of Zr(IV)‐based porphyrinic metal‐organic framework (MOF) and NaYF₄,Yb,Er upconverting nanoparticles (UCNPs) for photodynamic therapy (PDT) is reported. MOF NPs generate singlet oxygen (¹O₂) upon photoirradiation with visible light without the need for additional small molecule, diffusional photosensitizers such as porphyrins. Using DNA as a templating agent, well‐defined MOF–UCNP clusters are produced where UCNPs are spatially organized around a centrally located MOF NP. Under NIR irradiation, visible light emitted from the UCNPs is absorbed by the core MOF NP to produce ¹O₂ at significantly greater amounts than what can be produced from simply mixing UCNPs and MOF NPs. The MOF–UCNP core–satellite superstructures also induce strong cell cytotoxicity against cancer cells, which are further enhanced by attaching epidermal growth factor receptor targeting affibodies to the PDT clusters, highlighting their promise as theranostic photodynamic agents.     

A Singlet Oxygen Generating Agent by Chirality‐dependent Plasmonic Shell‐Satellite Nanoassembly

Photodynamic therapy (PDT) agent, which generates singlet oxygen (¹O₂) under light, has attracted significant attention for its broad biological and medical applications. Here, DNA‐driven shell–satellite (SS) gold assemblies as chiral photosensitizers are first fabricated. The chiral plasmonic nanostructure, coupling with cysteine enantiomers on its surface, exhibits intense chiroplasmonic activities (?40.2 ± 2.6 mdeg) in the visible region. These chiral SS nanoassemblies have high reactive oxygen species generating efficiency under circular polarized light illumination, resulting in a ¹O₂ quantum yield of 1.09. Meanwhile, it is found that SS could be utilized as PDT agent with remarkable efficiency under right circular polarized light irradiation in vitro and in vivo, allowing X‐ray computed tomography (CT) and photoacoustics (PA) imaging for tumors simultaneously. The achievements reveal that the enantiomer‐dependent and structure‐induced nanoassemblies play an important role in PDT effects. The present researches open up a new avenue for cancer diagnose and therapy using chiral nanostructures as multifunctional platform.     

Dual‐Stage Light Amplified Photodynamic Therapy against Hypoxic Tumor Based on an O2 Self‐Sufficient Nanoplatform

Tumor hypoxia severely limits the efficacy of traditional photodynamic therapy (PDT). Here, a liposome‐based nanoparticle (designated as LipoMB/CaO₂) with O₂ self‐sufficient property for dual‐stage light‐driven PDT is demonstrated to address this problem. Through a short time irradiation, ¹O₂ activated by the photosensitizer methylene blue (MB) can induce lipid peroxidation to break the liposome, and enlarge the contact area of CaO₂ with H₂O, resulting in accelerated O₂ production. Accelerated O₂ level further regulates hypoxic tumor microenvironment and in turn improves ¹O₂ generation by MB under another long time irradiation. In vitro and in vivo experiments also demonstrate the superior competence of LipoMB/CaO₂ to alleviate tumor hypoxia, suppress tumor growth and antitumor metastasis with low side‐effect. The O₂ self‐sufficient LipoMB/CaO₂ nanoplatform with dual‐stage light manipulation is a successful attempt for PDT against hypoxic tumor.     

A series of novel double perovskite oxides NaMTi<Subscript>2</Subscript>O<Subscript>6</Subscript> (M = Eu,Sm, and Gd): preparation,characterization and photocatalytic studies under visible and solarlight irradiation

The photocatalytic activity of sol–gel synthesized double perovskite type oxides NaEuTi₂O₆(NETO), NaSmTi₂O₆ (NSTO), and NaGdTi₂O₆ (NGTO) powders on degradation of methylene blue (MB) dye was demonstrated for the first time under visible light as well as sunlight irradiation. The obtained samples were characterized by X-ray diffraction, UV–Visible diffuse reflectance spectroscopy and scanning electron microscopy equipped with X-ray energy-dispersion spectrometry. All the three samples have shown photocatalytic activity for degradation of MB under sunlight and visible light irradiation and their photocatalytic activity followed the order of NGTO > NETO > NSTO. The superior activity of NGTO is ascribed to the higher amount of hydroxyl radicals generated in the photocatalytic reaction.     

Vacuum‐Drying Processed Micrometer‐Thick Stable CsPbBr3 Perovskite Films with Efficient Blue‐To‐Green Photoconversion

Metal halide perovskite materials have attracted great attention owing to their fascinating optoelectronic characteristics and low cost fabrication via facile solution processing. One of the potential applications of these materials is to employ them as color‐conversion layers (CCLs) for visible blue light to achieve full‐color displays. However, obtaining thick perovskite films to realize complete color conversion is a key challenge. Here, the fabrication of micrometer‐level thick CsPbBr₃ perovskite films is presented through a facile vacuum drying approach. An efficient green photoconversion is realized in a 3.8 µm thick film from blue light @ 463 nm. For a back luminance of 1000 cd m^?2, the brightness of the resulting green emission can reach as high as 200 cd m^?2. Furthermore, only ≈2% of decay in brightness is observed when the films are tested after 18 days of exposure to ambient environment. In addition, a potential design is also proposed for full‐color displays with perovskite materials incorporated as CCLs.     

Distinguishable Detection of Ultraviolet,Visible, and Infrared Spectrum with High‐Responsivity Perovskite‐Based Flexible Photosensors

Distinguishable detection of the ultraviolet, visible, and infrared spectrum is promising and significant for the super visual system of artificial intelligences. However, it is challenging to provide a photosensor with such broad spectral response ability. In this work, the ultraviolet, visible, and infrared spectrum is distinguished by developing serial photosensors based on perovskite/carbon nanotube hybrids. Oraganolead halide perovskites (CH₃NH₃PbX₃) possess remarkable optoelectronic properties and tunable optical band gaps by changing the halogens, and integration with single‐walled carbon nanotubes can further improve their photoresponsivities. The CH₃NH₃PbCl₃‐based photosensor shows a responsivity up to 10⁵ A W^?1 to ultraviolet and no obvious response to visible light, which is superior to that of most ultraviolet sensors. The CH₃NH₃PbBr₃‐based photosensor exhibits a high responsivity to visible light. Serial devices of the two hybrid photosensors with comparable electric and sensory performances can distinguish the spectrum of ultraviolet, visible, and infrared even with varying light intensities. The photosensors also demonstrate excellent mechanical flexibility and bending stability. By taking full advantages of the oraganolead halide perovskites, this work provides flexible high‐responsivity photosensors specialized for ultraviolet, and gives a simple strategy for distinguishable detection of ultraviolet, visible, and infrared spectrum based on the serial flexible photosensors.     

Ultrahigh‐Performance Self‐Powered Flexible Double‐Twisted Fibrous Broadband Perovskite Photodetector

Self‐powered flexible photodetectors without an external power source can meet the demands of next‐generation portable and wearable nanodevices; however, the performance is far from satisfactory becuase of the limited match of flexible substrates and light‐sensitive materials with proper energy levels. Herein, a novel self‐powered flexible fiber‐shaped photodetector based on double‐twisted perovskite–TiO₂–carbon fiber and CuO–Cu₂O–Cu wire is designed and fabricated. The device shows an ultrahigh detectivity of 2.15 × 10¹³ Jones under the illumination of 800 nm light at zero bias. CuO–Cu₂O electron block bilayer extends response range of perovskite from 850 to 1050 nm and suppresses dark current down to 10^?11 A. The fast response speed of less than 200 ms is nearly invariable after dozens of cycles of bending at the extremely 90 bending angle, demonstrating excellent flexibility and bending stability. These parameters are comparable and even better than reported flexible and even rigid photodetectors. The present results suggest a promising strategy to design photodetectors with integrated function of self‐power, flexibility, and broadband response.     

Design for Highly Piezoelectric and Visible/Near‐Infrared Photoresponsive Perovskite Oxides

Defect‐engineered perovskite oxides that exhibit ferroelectric and photovoltaic properties are promising multifunctional materials. Though introducing gap states by transition metal doping on the perovskite B‐site can obtain low bandgap (i.e., 1.1–3.8 eV), the electrically leaky perovskite oxides generally lose piezoelectricity mainly due to oxygen vacancies. Therefore, the development of highly piezoelectric ferroelectric semiconductor remains challenging. Here, inspired by point‐defect‐mediated large piezoelectricity in ferroelectrics especially at the morphotropic phase boundary (MPB) region, an efficient strategy is proposed by judiciously introducing the gap states at the MPB where defect‐induced local polar heterogeneities are thermodynamically coupled with the host polarization to simultaneously achieve high piezoelectricity and low bandgap. A concrete example, Ni²⁺‐mediated (1–x)Na_0.5Bi_0.5TiO₃‐xBa(Ti_0.5Ni_0.5)O_3–δ (x = 0.02–0.08) composition is presented, which can show excellent piezoelectricity and unprecedented visible/near‐infrared light absorption with a lowest ever bandgap ≈0.9 eV at room temperature. In particular, the MPB composition x = 0.05 shows the best ferroelectricity/piezoelectricity (d₃₃ = 151 pC N^–1, Pr = 31.2 μC cm^–2) and a largely enhanced photocurrent density approximately two orders of magnitude higher compared with classic ferroelectric (Pb,La)(Zr,Ti)O₃. This research provides a new paradigm for designing highly piezoelectric and visible/near‐infrared photoresponsive perovskite oxides for solar energy conversion, near‐infrared detection, and other multifunctional applications.     

Single‐Component TiO2 Tubular Microengines with Motion Controlled by Light‐Induced Bubbles

In this work, light‐controlled bubble‐propelled single‐component metal oxide tubular microengines have for the first time been demonstrated. For such a simple single‐component TiO₂ tubular microengine in H₂O₂ aqueous solution under UV irradiation, when the inner diameter and length of the tube are regulated, the O₂ molecules will nucleate and grow into bubbles preferentially on the inner concave surface rather than on the outer surface, resulting in a vital propulsion of the microengine. More importantly, the motion state and speed can be modulated reversibly, fast (the response time is less than 0.2 s) and wirelessly by adjusting UV irradiation. Consequently, the as‐developed TiO₂ tubular microengine promises potential challenged applications related to photocatalysis, such as “on‐the‐fly” photocatalytic degradation of organic pollutes and photocatalytic inactivation of bacteria due to the low cost, single component, and simple structure, as well as the facile fabrication in a large‐scale.     

In Situ Fabrication of Vertical Multilayered MoS2/Si Homotype Heterojunction for High‐Speed Visible–Near‐Infrared Photodetectors

c2D transition metal dichalcogenides (TMDCs)‐based heterostructures have been demonstrated to achieve superior light absorption and photovoltaic effects theoretically and experimentally, making them extremely attractive for realizing optoelectronic devices. In this work, a vertical multilayered n‐MoS₂/n‐silicon homotype heterojunction is fabricated, which takes advantage of multilayered MoS₂ grown in situ directly on plane silicon. Electrical characterization reveals that the resultant device exhibits high sensitivity to visible–near‐infrared light with responsivity up to 11.9 A W^–1. Notably, the photodetector shows high‐speed response time of ≈30.5 µs/71.6 µs and capability to work under higher pulsed light irradiation approaching 100 kHz. The high response speed could be attributed to a good quality of the multilayer MoS₂, as well as in situ device fabrication process. These findings suggest that the multilayered MoS₂/Si homotype heterojunction have great potential application in the field of visible–near‐infrared detection and might be used as elements for construction of high‐speed integrated optoelectronic sensor circuitry.     

Ultrathin and Small‐Size Graphene Oxide as an Electron Mediator for Perovskite‐Based Z‐Scheme System to Significantly Enhance Photocatalytic CO2 Reduction

The judicious design of efficient electron mediators to accelerate the interfacial charge transfer in a Z‐scheme system is one of the viable strategies to improve the performance of photocatalysts for artificial photosynthesis. Herein, ultrathin and small‐size graphene oxide (USGO) nanosheets are constructed and employed as the electron mediator to elaborately exploit an efficient CsPbBr₃‐based all‐solid‐state Z‐scheme system in combination with α‐Fe₂O₃ for visible‐light‐driven CO₂ reduction with water as the electron source. CsPbBr₃ and α‐Fe₂O₃ can be closely anchored on USGO nanosheets, owing to the existence of interfacial strong chemical bonding behaviors, which can significantly accelerate the photogenerated carrier transfer between CsPbBr₃ and α‐Fe₂O₃. The resultant improved charge separation efficiency endows the Z‐scheme system exhibiting a record‐high electron consumption rate of 147.6 µmol g^?1 h^?1 for photocatalytic CO₂‐to‐CO conversion concomitant with stoichiometric O₂ from water oxidation, which is over 19 and 12 times higher than that of pristine CsPbBr₃ nanocrystals and the mixture of CsPbBr₃ and α‐Fe₂O₃, respectively. This work provides a novel and effective strategy for improving the catalytic activity of halide‐perovskite‐based photocatalysts, promoting their practical applications in the field of artificial photosynthesis.     

A Self‐Powered and Flexible Organometallic Halide Perovskite Photodetector with Very High Detectivity

Flexible and self‐powered photodetectors (PDs) are highly desirable for applications in image sensing, smart building, and optical communications. In this paper, a self‐powered and flexible PD based on the methylammonium lead iodide (CH₃NH₃PBI₃) perovskite is demonstrated. Such a self‐powered PD can operate even with irregular motion such as human finger tapping, which enables it to work without a bulky external power source. In addition, with high‐quality CH₃NH₃PBI₃ perovskite thin film fabricated with solvent engineering, the PD exhibits an impressive detectivity of 1.22 × 10¹³ Jones. In the self‐powered voltage detection mode, it achieves a large responsivity of up to 79.4 V mW^?1 cm^?2 and a voltage response of up to ≈90%. Moreover, as the PD is made of flexible and transparent polymer films, it can operate under bending and functions at 360 ° of illumination. As a result, the self‐powered, flexible, 360 ° omnidirectional perovskite PD, featuring high detectivity and responsivity along with real‐world sensing capability, suggests a new direction for next‐generation optical communications, sensing, and imaging applications.     

An integrated solution for NOx‐reduction and ‐control under lean‐burn conditions

Upcoming emission regulations order highly effective NO_x‐reduction systems in lean‐burn engines requiring new catalytic materials and integrated control of the reduction process. Thus, new approaches for NO_x‐reduction and its monitoring over an On‐Board‐Diagnostic (OBD) system are suggested throughout the globe. A promising attempt is the development of a catalytic system having an integrated NO_x‐sensor, based on selective catalytic reduction process and impedance sensors. The study displays the results achieved both with a perovskite type of self‐regenerative catalyst functioning by H₂‐reductant and with impedance NO_x‐sensors. The catalysts were tested at the temperature range of 150 °C to 360 °C yielding NO_x conversion rates of 92 % with high selectivity to N₂. Impedance sensors having NiCr₂O₄‐ and NiO‐SE and PYSZ‐ and FYSZ‐electrolytes are developed and tested at 600 °C under lean atmosphere (5 vol. % O₂). Better sensing behaviour towards NO and lower cross‐selectivity towards O₂, CO, CO₂ and CH₄ have been observed with sensors having NiO‐SE.     

From UV to Near‐Infrared Light‐Responsive Metal–Organic Framework Composites: Plasmon and Upconversion Enhanced Photocatalysis

The exploitation of photocatalysts that harvest solar spectrum as broad as possible remains a high‐priority target yet grand challenge. In this work, for the first time, metal–organic framework (MOF) composites are rationally fabricated to achieve broadband spectral response from UV to near‐infrared (NIR) region. In the core–shell structured upconversion nanoparticles (UCNPs)‐Pt@MOF/Au composites, the MOF is responsive to UV and a bit visible light, the plasmonic Au nanoparticles (NPs) accept visible light, whereas the UCNPs absorb NIR light to emit UV and visible light that are harvested by the MOF and Au once again. Moreover, the MOF not only facilitates the generation of “bare and clean” Au NPs on its surface and realizes the spatial separation for the Au and Pt NPs, but also provides necessary access for catalytic substrates/products to Pt active sites. As a result, the optimized composite exhibits excellent photocatalytic hydrogen production activity (280 µmol g^?1 h^?1) under simulated solar light, and the involved mechanism of photocatalytic H₂ production under UV, visible, and NIR irradiation is elucidated. Reportedly, this is an extremely rare study on photocatalytic H₂ production by light harvesting in all UV, visible, and NIR regions.     

Mesoporous Polymeric Cyanamide‐Triazole‐Heptazine Photocatalysts for Highly‐Efficient Water Splitting

Conjugated polymers are promising light harvesters for water reduction/oxidation due to their simple synthesis and adjustable bandgap. Herein, both cyanamide and triazole functional groups are first incorporated into a heptazine‐based carbon nitride (CN) polymer, resulting in a mesoporous conjugated cyanamide‐triazole‐heptazine polymer (CTHP) with different compositions by increasing the quantity of cyanamide/triazole units in the CN backbone. Varying the compositions of CTHP modulates its electronic structures, mesoporous morphologies, and redox energies, resulting in a significantly improved photocatalytic performance for both H₂ and O₂ evolution under visible light irradiation. A remarkable H₂ evolution rate of 12723 µmol h^?1 g^?1 is observed, resulting in a high apparent quantum yield of 11.97% at 400 nm. In parallel, the optimized photocatalyst also exhibits an O₂ evolution rate of 221 µmol h^?1 g^?1, 9.6 times higher than the CN counterpart, with the value being the highest among the reported CN‐based bifunctional photocatalysts. This work provides an efficient molecular engineering approach for the rational design of functional polymeric photocatalysts.     

Anomalous and Polarization‐Sensitive Photoresponse of Td‐WTe2 from Visible to Infrared Light

Recently, an emergent layered material T_d‐WTe₂ was explored for its novel electron–hole overlapping band structure and anisotropic inplane crystal structure. Here, the photoresponse of mechanically exfoliated WTe₂ flakes is investigated. A large anomalous current decrease for visible (514.5 nm), and mid‐ and far‐infrared (3.8 and 10.6 µm) laser irradiation is observed, which can be attributed to light‐induced surface bandgap opening from the first‐principles calculations. The photocurrent and responsivity can be as large as 40 µA and 250 A W^?1 for a 3.8 µm laser at 77 K. Furthermore, the WTe₂ anomalous photocurrent matches its in‐plane crystal structure and exhibits light polarization dependence, maximal for linear laser polarization along the W atom chain a direction and minimal for the perpendicular b direction, with the anisotropic ratio of 4.9. Consistently, first‐principles calculations confirm the angle‐dependent bandgap opening of WTe₂ under polarized light irradiation. The anomalous and polarization‐sensitive photoresponses suggest that linearly polarized light can significantly tune the WTe₂ surface electronic structure, providing a potential approach to detect polarized and broadband lights up to far infrared range.