Search

[Display omitted] • Unique popcorn-like nanosphere structure endows abundant active sites. • DFT theoretical calculation reveal the transfer pathway of charges. • Hierarchical tandem heterojunctions promote the separation of carriers. • The H 2 production efficiency is 50 times higher than the unmodified material. • It offers a new method for green energy conversion and hydrogen energy separation. Heterojunction engineering is widely recognized as one of the most effective strategies for enhancing photocatalytic performance and suppressing photocorrosion by promoting efficient carrier separation and transfer. In this work, popcorn-like ZnCdS-MoS 2 @Co 3 O 4 nanospheres with large specific surface areas and hierarchical tandem heterojunctions were synthesized via one-pot in-situ self-assembly combined with hole-driven photodeposition. Based on the highly uniform dispersion of MoS 2 as an electron collector in the system and precise deposition of Co 3 O 4 as a photogenerated hole collector driven by photogenerated carriers at the hole enrichment position, it can efficiently catalyze the photocatalytic hydrogen evolution in water. Compared to ZnCdS, the optimized ZCS-M@0.5C exhibits a 50-fold increase in visible-light-driven hydrogen evolution efficiency, achieving 18.73 mmol·h−1·g−1 and maintaining stability after a 20-hour cycle test. Additionally, the apparent quantum yield reaches a remarkable 10.11% at 420 nm. Experimental characterization tests and differential charge density analysis have confirmed the efficient ability of Pt-like MoS 2 to induce electron separation and transportation, while p-type semiconductor Co 3 O 4 accumulates holes through the p-n junction. Both theoretical and experimental evidence show that the incorporation of dual-internal electric fields facilitates bi-directional charge separation and rapid transfer. The photocatalytic performance is improved through a synergistic effect involving hierarchical tandem heterojunctions. This work presents a novel approach to fabricating highly efficient photocatalysts with multi-heterojunctions through synergistic effects. [ABSTRACT FROM AUTHOR]

In the present work, we shed light on a new excited state intermolecular dynamical mechanism for 2-(4′-N, N-Dimethylaminophenyl)imidazo[4,5-b]pyridine (DMAPIP) in methanol (MeOH) solvent. Given intermolecular hydrogen bond connection modes, we confirm that DMAPIP-2MeOH (two MeOH molecules connecting with DMAPIP system) is the most stable and reasonable form in both S 0 and S 1 states rather than DMAPIP-MeOH. Further, we make a new attribution that excited state multiple protons transfer (ESMPT) process can occur with a low potential barrier in the S 1 state for DMAPIP-2MeOH, and rotation process of twisting dimethylamino or dimethylaminophenyl moiety is nonexistent. Our work not only clarifies how to judge numbers of solvent molecules participating in ESMPT reaction, but paves the way for further investigating intermolecular multiple hydrogen bonds interactions in biological field. [ABSTRACT FROM AUTHOR]

BaTiO 3 /TiO 2 nanocomposite films with varied amount of BaTiO 3 are fabricated and applied as photoanodes for dye-sensitized solar cells (DSCs) and demonstrated enhanced power conversion efficiency. Ferroelectricity of BaTiO 3 in the film after subjected to a annealing process up to 450 °C is examined by Switching Spectroscopy Piezoresponse Force Microscopy (SSPFM). The highest performance is achieved in 1.0 wt% BaTiO 3 addition as a result of increased photocurrent density (J sc ) and fill factor ( FF ), regardless of reduction of dye-loading. Electrochemical impedance spectroscopy (EIS) measurements at different bias voltages (≦ V oc ) in dark suggest that ferroelectric dipole induced electric field has positive effects on enhancing electron mobility and suppressing charge recombination. Although more detailed experiments are needed in designing of the nanocomposite films for compensating characteristics of dye-loading and electron mobility, introduction of ferroelectric dipole induced electric field into the photoanode would be a good strategy in achieving further improvement of power conversion efficiency of DSCs through improved charge transfer properties. [ABSTRACT FROM AUTHOR]

Tetracenes and their derivatives are widely used in organic semiconductors for the advantages of small reorganization energies and large electronic couplings. The influences of long alkyl chain on charge transfer mobility of two bistetracene derivatives are investigated theoretically. The results show that the introduction of long alkyl chains would lead to a more compact packing, and increase electronic coupling, but reduce intermolecular distance. However, the introduction of long alkyl chains has little influence on reorganization energy. This provides a new understanding of the introduction of long alkyl chain on designing new high efficiency organic semiconductors. [ABSTRACT FROM AUTHOR]

In this letter, the charge transfer mobility of naphthalenediimide (NDTI) derivative is investigated. By employing the normal-mode analysis and bond length relaxation analysis, the influences of chemical elements on reorganization energies and intermolecular electronic couplings are investigated in NDTI derivative. The results show that the introduction of atom O would decrease reorganization energy in hole-hopping process and increase electronic coupling. This analysis encourages the molecular and material design in organic semiconductors. [ABSTRACT FROM AUTHOR]

The ZnO nanostructure is difficult to apply in sewage treatment because of its low photocatalytic efficiency, narrow spectrum response, high photogenerated carrier recombination rate, and difficult retrieval from aqueous solution. CuO coupling could improve both the absorption of visible light and photocatalytic performance of ZnO nanoparticles. In this paper, the ZnO/CuO hollow microspheres was fabricated by a self-assembly method without a template. The experimental results showed that ZnO/CuO hollow microspheres (4 μm) were successfully prepared via the hydrothermal method. CuO coupling greatly ameliorated the photocatalytic performance of ZnO microspheres under natural solar light or visible light, and the photodegrading rate in natural solar light was approximately 6 times greater than that of pure ZnO spheres. In addition, ZnO/CuO spheres showed good photocatalytic stability. The enhanced catalytic activity is associated with the reduced impedance of the ZnO sphere via CuO coupling, which promotes the separation of e−/h+ carriers and enlarges the spectrum response to visible light. • ZnO/CuO hollow microspheres were prepared in situ without a template. • The effective heterostructure of ZnO and CuO was constructed. • ZnO/CuO hollow microspheres possess superior catalytic activity under natural sunlight. • CuO coupling can reduce impedance and facilitate transfer charge carriers. [ABSTRACT FROM AUTHOR]

The construction of semiconductor heterojunctions is regarded as an efficient strategy for promoting photogenerated carrier transfer and enhancing photocatalytic performance. [1] Moreover, the in-situ self-assembly method of the main catalyst and the cocatalyst is believed to overcome the shortcomings of the traditional surface loading method and provide a more efficient hydrogen evolution reaction capability. In this work, Zn-Cd-Mo-S quaternary metal sulfide mesoporous nanospheres were generated by in-situ self-assembly via a one-step mild hydrothermal method. A photocatalyst with a double-heterojunction synergistic structure and a large specific surface area was constructed to form a high-speed charge transfer channel as a mechanism to promote photocatalytic hydrogen production. The best quaternary catalyst ZCM 5 S has a hydrogen evolution yield of 23.32 mmol h−1 g−1, which is 53 times and 11 times that of the corresponding binary (CdS) and ternary (ZnCdS) metal sulfides, respectively, and still has high stability within 20 h. Furthermore, the ZCM 5 S gets an apparent quantum efficiency (AQE) of 6.9 % at 420 nm. Through further analysis, such as photoluminescence (PL) and photoelectrochemical, etc., the enhanced photocatalytic performance of ZCM 5 S can be attributed to the synergistic effect of the heterojunction between ZnS and CdS and the heterojunction between ZnCdS and MoS 2. In addition, the Pt-like structure of molybdenum sulfide cocatalyst can lead to efficient photoinduced charge separation and transfer. Meanwhile, the mesoporous structure endows the material with abundant reactive sites and increases the catalytic reaction efficiency. The unique in situ construction method of this work also provides a reference for the design and synthesis of heterojunction quaternary catalysts for green energy conversion. [Display omitted] • The mesoporous structure increases the reactive site area. • The double heterojunction synergy facilitates exciton transfer. • Quaternary sulfides outperform their parent materials. • A method for in situ syntheses of quaternary metal sulfides is proposed. • The main and co-catalyst one-step method is beneficial and feasible. [ABSTRACT FROM AUTHOR]

Hollow hetero-nanosheet arrays have attracted great attention due to their efficient catalytic abilities for water splitting. We successfully fabricated ZIF-67-derived hollow CoMoS3.13/MoS2 nanosheet arrays on carbon cloth in situ through a two-step heating-up hydrothermal method, in which the MoS2 nanosheets were suitably distributed on the surface of the hollow CoMoS3.13 nanosheet arrays. There was a distinct synergistic effect between CoMoS3.13 and MoS2, and a large number of defective and disordered interfaces were formed, which improved the charge transfer rate and provided abundant electrochemical active sites. CMM 0.5, with the optimal Mo doping concentration of 0.5 mmol, exhibited the best catalytic properties. The overpotential values of CMM 0.5 at 10 mA cm−2 were only 107 and 169 mV for the HER and OER, respectively, and it had nearly 100% faradaic efficiency. A dual-electrode electrolytic cell assembled with CMM 0.5 required a voltage of only 1.507 V at 10 mA cm−2 for overall water splitting, and it displayed remarkable long-term durable bifunctional stability. [ABSTRACT FROM AUTHOR]

An Fe-doped Ni0.85Se nanosheets array on Ni foam was synthesized successfully through a one-step solvothermal method as an effective binder-free multifunctional catalyst for the hydrogen evolution reaction (HER), the oxygen evolution reaction (OER), overall water splitting and supercapacitors. As an electrocatalyst, the 0.8%Fe–Ni0.85Se nanosheets array only required a small overpotential of 120 mV and a Tafel slope of 34.11 mV dec−1 to deliver a current density of 10 mA cm−2 for the HER. The 2%Fe–Ni0.85Se nanosheets array can provide a large current density of 100 mA cm−2 at an overpotential of 1.54 V and a Tafel slope of 73.40 mV dec−1 for the OER. The 2%Fe–Ni0.85Se(+)‖0.8%Fe–Ni0.85Se(−) electrolyzer only needed a low cell potential of 1.52 V to reach 100 mA cm−2 in 1.0 M KOH and exhibited long-term stability for 40 h. The remarkable HER, OER and overall water splitting properties of the Fe-doped Ni0.85Se nanosheets array mainly originated from the unique nanosheets array morphology, high electronic conductivity, and large effective electrochemical active surface induced by Fe doping. In addition, the 2%Fe–Ni0.85Se nanosheets showed supercapacitive properties, with a maximum specific capacitance of 1103.5 F g−1 at a current density of 1 A g−1, good cycling stability with a capacitance retention of 82% after 1000 cycles and a low charge transfer resistance of 0.0092 Ω. [ABSTRACT FROM AUTHOR]

• The Sba modified Ti 3 C 2 Tx MXene is synthesized to modify buried interface to achieve high PCE in PSCs. • The MX-Sba formed a double-sided association with SnO 2 and perovskite to passivate both-side defects. • Intramolecular charge transfer within MX-Sba accelerates the interfacial charge transfer of PSCs. • The MX-Sba optimized the SnO 2 /PVK interfacial band arrangement. Buried interface engineering is essential for improving optoelectronic properties and the charge extraction process to achieve high efficient perovskite solar cells (PSCs). Herein, we designed and prepared the 4-Sulfamoylbenzoic acid (Sba) functionalized MXene (MX-Sba) nanosheets to modify buried interface of PSCs. Such functionalized strategy enabled the MX-Sba to form a double-sided association with SnO 2 and perovskite to passivate both-side defects due to the coexistence of F groups within MXene and NH 2 and S O groups of Sba. Compared to the MXene, MX-Sba not only further improved the conductivity of SnO 2 layer, but also helped to achieve the desirable interfacial band arrangement. As a result, the MX-Sba based PSCs achieved the highest photoelectric conversion efficiency of 23.49 % with improved stability. This work provides an effective strategy for buried interface engineering in PSCs, which is also applicable for other photoelectric devices. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • TFP coordinates with Pb defects and forms hydrogen bonds with MA+ and FA+. • The Ag@TFP layer enhances light absorption and produces more hot carriers. • The Ag@TFP layer enhances the V bi and match the energy levels of the PSCs. • A PCE of 23.86% has been achieved in PSCs based on Ag@TFP-TFP synergistic strategy. The development of multi-functional synergetic strategy with defect passivation and optical management is expected to further improve the photovoltaic performance of perovskite solar cells (PSCs). Herein, the small organic molecule of 4-trifluoromethyl pyridine (TFP) and Ag nanoparticle modified by TFP (Ag@TFP) with local surface plasmon resonance (LSPR) effects were introduced into PSCs. After investigating their different intervention ways in PSCs, a novel technique has been proved to own the ability to achieve the best photovoltaic performance of PSCs, i.e. TFP was introduced into the perovskite layer by anti-solvent method, and then a layer of Ag@TFP was deposited on the perovskite layer. The TFP can both coordinate with Pb related defects and form hydrogen bonds with MA+ and FA+ to effectively inhibit ion migration, so that the perovskite films with high crystal quality and improved stability can be obtained. The further deposition of Ag@TFP enhances the light absorption of perovskite via far-field light scattering effects and produces hot electrons for injection, so that the Jsc and Voc can be greatly increased. Meanwhile, an enhanced near-field electromagnetic field of Ag@TFP increases the build-in field of device, and a more matched energy level alignment has been formed, which greatly accelerates the charge transfer from perovskite to HTL. As a result, the highest PCE of 23.86 % has been achieved in the Ag@TFP-TFP based Cs 0.069 FA 0.826 MA 0.105 Pb(I 0.955 Br 0.045) 3 PSCs. This work not only provides an effective approach to improve the photovoltaic performance of PSCs, but also open a new gate to design synergetic strategy with multifunction for prompting the development of PSCs. [ABSTRACT FROM AUTHOR]

Understanding the phase regulation mechanism of BaTiO 3 synthesized by a hydrothermal method is a complicated and challenging task. Here, we successfully prepared cubic and tetragonal BaTiO 3 single nanocrystals by changing the ratio of water and ethanol in the solvent. We confirm that the BaTiO 3 phase is mainly affected by the hydroxylation process due to the reaction with solvent. In particular, ethanol can be catalytically oxidized by titanium atoms, cause BaTiO 3 hydroxylation and promote the formation of a cubic phase. In the mixed solution of ethanol and water, the hydroxylation process is suppressed, which facilitates the formation of the tetragonal phase. The relationship framework between the solvent ratio, phase structure and hydroxyl defects of BaTiO 3 is established. Tetragonal BaTiO 3 with fewer hydroxyl defects can promote charge transfer and surface reaction after polarization, thereby enhancing their photoelectric catalytic performance. This work provides references for the controllable synthesis of ferroelectric nanocrystals by hydrothermal methods and new insight for the utilization of polarization in photoelectrocatalysis applications. [Display omitted] • Cubic BaTiO 3 were prepared in pure ethanol or water solution due to the hydroxylation effect in the hydrothermal process. • In the mixed solution of ethanol and water, the hydroxylation process was suppressed and tetragonal BaTiO 3 were generated. • The polarization electric field of tetragonal BaTiO 3 has a significant imapct on their photoelectrocatalytic performance. [ABSTRACT FROM AUTHOR]

Octahedral Cu 2 O-Au composite microstructures (CMSs) were synthesized with a facile in situ method and were attempted as surface-enhanced Raman scattering (SERS) substrates. The density of the Au nanoparticles (NPs) on the surface of the octahedral Cu 2 O microcrystals can be controlled by tuning the concentration of the gold precursor, which can further influence the SERS activity of the Cu 2 O-Au CMSs system. The CMSs system exhibited a charge transfer from Au to Cu 2 O. Furthermore, metallic NPs deposited on the semiconductor material formed a local electromagnetic field, which altered the interfacial charge distribution. The SERS signal enhancement from the Cu 2 O-Au CMSs system is attributed to a combination of electromagnetic and chemical enhancement mechanisms occurring simultaneously at the semiconductor-metal interface. Overall, the proposed CMSs system will provide a new model for SERS study and application. [ABSTRACT FROM AUTHOR]

BiVO 4 film coupled with resorcinol–formaldehyde resin (RFS) nanoparticles to form BiVO 4 /RFS heterojunction film as photoanode for solar water oxidation. The conduction and valence band potential of RFS nanoparticles were lower than those of BiVO 4 , and the surface holes and electrons could be directionally transferred to RFS nanoparticles and BiVO4 film, respectively. [Display omitted] • BiVO 4 /RFS film photoanodes were prepared by coupling BiVO 4 films with resorcinol–formaldehyde resin nanoparticles for solar water oxidation. • The light harvesting and electrochemical properties of the optimal BiVO 4 /RFS film was close to the BiVO 4 film. • Better water oxidation activity, kinetics and stability were observed on the BiVO 4 /RFS film photoanode. • The conduction and valence band potential of RFS nanoparticles were lower than those of BiVO 4 , and their surface holes and electrons could be directionally transferred to RFS nanoparticles and BiVO 4 film, respectively. The poor properties of carrier separation and transfer on BiVO 4 surface are two major bottlenecks for nanostructured BiVO 4 photoanodes during solar water oxidation. Herein, BiVO 4 /resorcinol–formaldehyde resin (BiVO 4 /RFS) heterojunction films were prepared by coupling resorcinol–formaldehyde resin (RFS) nanoparticles on BiVO 4 films' surface, and investigated as photoanodes for solar water oxidation. The light harvesting and electrochemical properties of the resultant BiVO 4 /RFS film was close to the BiVO 4 film, but its carrier radiative recombination was weakened significantly. Relative to the BiVO 4 film photoanode, better water oxidation activity, kinetics and stability were observed on the BiVO 4 /RFS film photoanode. The conduction and valence band potential of RFS nanoparticles were discovered to be lower than those of BiVO 4 , and the surface photogenerated holes and electrons could be directionally transferred to RFS nanoparticles and BiVO 4 film, respectively. The higher solar water oxidation performance on the BiVO 4 /RFS photoanode was mainly originated from the separation and transfer of surface carrier through the BiVO 4 /RFS coupling interfaces under AM 1.5G irradiation. The present work could provide inspiration in the design and development of similar heterojunction materials for solar water splitting. [ABSTRACT FROM AUTHOR]

[Display omitted] • Inorganic HAuCl 4 doping combined organic NPB post-treatment strategy was proposed. • High PCE of 19.20% for Au@PEDOT:PSS/NPB PSCs is achieved on rigid substrate. • Flexible Au@PEDOT:PSS/NPB PSCs achieve 14.04% PCE with strong wrinkle resistance. • Improved hysteresis and stability of PSCs are realized via synchronous regulation. The further improvements in optoelectronic properties, hydrophobicity of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) hole transport layers, as well as regulation of defect states within devices are essential to promote the continued development of inverted p-i-n rigid and flexible planar perovskite solar cells (PSCs). However, the strong hygroscopicity, poor surface morphology, lower work function and coil configuration of pristine PEDOT:PSS films are detrimental to their own performance and growth dynamics process of perovskites, often resulting in sever energy losses and poor device performance. Herein, hydrogen tetrachloroaurate (III) hydrate (HAuCl 4 ·3H 2 O) additive is combined with a conductive N,N'-Bis-(1-naphthalenyl)-N,N'-bis-phenyl-(1,1′-biphenyl)-4,4′-diamine (NPB) buffer layer to boost device performance by systematically modulating PEDOT:PSS and perovskite film. Wherein, the redox reaction between PEDOT:PSS and HAuCl 4 can cause phase segregation of PEDOT:PSS, improving the hydrophobicity, electrical conductivity, work function and surface morphology of the films. The reduced gold nanoparticles will produce localized surface plasmon resonance effects, thus enhancing the utilization of solar radiation by perovskite films. Furthermore, the suitable energy level alignment of NPB layer relative to perovskite and Au@PEDOT:PSS films will sufficiently exploit the dissociative excitons to facilitate effective hole transport, and the N atoms in NPB can also passivate defects at the interface by binding to uncoordinated Pb2+ ions, thereby reducing non-radiative open-circuit voltage loss and increasing short-circuit current density. A high power conversion efficiency (PCE) of 19.20% can be achieved for MA 0.85 FA 0.15 PbI 3 based p-i-n PSCs with negligible hysteresis and enhanced stability of devices. Similarly, the corresponding flexible device achieves a PCE of 14.04% with improved crumpling durability throughout low temperature preparation conditions below 140 °C. Our work presents a facile method to prepare high-efficient inverted PSCs while achieving improved long-term device stability. [ABSTRACT FROM AUTHOR]

• Ag nanoparticles are anchored onto CuS sub-micron flowers to form composites. • The CuS@Ag electrodes exhibit enhanced charge storage property. • The decoration of Ag nanoparticles increases the electrical conductivity. • The generated electric field at the CuS/Ag interface accelerates the charge transfer. [Display omitted] In this reported work, Ag nanoparticles (NPs) decorated CuS sub-micron flowers are synthesized using a facile, solvothermal reaction coupled with a silver mirror reaction. The experimental results and theoretical calculations reveal that decorating the CuS with Ag NPs increases its intrinsic electrical conductivity and generates an electric field at the interface between Ag and CuS. These effects promote the efficient utilization of active materials and accelerate the interface charge transfer and electrochemical reaction kinetics. Consequently, the maximum specific capacity of the prepared CuS@Ag electrodes is found to be as high as 702 C g−1 at 2 A g−1, which is about 5 times greater than the pure CuS electrode. In addition, the capacity value is 400 C g−1 at 20 A g−1 and it exhibits 93% retention of the initial capacity after 5000 cycles at 10 A g−1. Moreover, a hybrid supercapacitor (HSC) device is assembled employing the CuS@Ag electrode as the positive electrode, which delivers an energy density of 51.1 Wh kg−1 at a power density of 798 W kg−1. These results demonstrate the promising potential of the fabricated CuS@Ag composites for further application in HSCs. [ABSTRACT FROM AUTHOR]

[Display omitted] • SrFe 12 O 19 /MoS 2 heterojunction composite are synthesized via hydrothermal method. • The exposed interface reduce the recombination rate of the photogenerated carrier. • The composite achieved high degradation rate with magnetic recovery ability. Photocatalysis is one of the most promising technologies in wastewater treatment. Efficient degradation under visible light and the recovery capability of the photocatalyst are crucial in real-word applications. Herein, M−type SrFe 12 O 19 was integrated into the surface of flowerlike MoS 2 microsphere via the hydrothermal method. As-prepared SrFe 12 O 19 /MoS 2 composite photocatalyst has effective visible light response and magnetic recovery ability. The SrFe 12 O 19 /MoS 2 composite achieved 97% degradation rate for methylene blue under visible light. The photocatalytic reaction rate of the SrFe 12 O 19 /MoS 2 composite was nearly twice that of pure MoS 2. Transient steady-state fluorescence spectrometry and electrochemical spectrometry revealed that an appropriate amount of SrFe 12 O 19 effectively improves the charge transfer rate and accelerates photoinduced charge carrier separation. The possible photocatalytic degradation mechanism of the SrFe 12 O 19 /MoS 2 composite with the p–n heterojunction was also examined. [ABSTRACT FROM AUTHOR]

• High pressure and high temperature were utilized to modify microscopic structures. • Stacking faults can sharply reduce the transfer resistance of electrons in MoS 2. • Distortions were uncovered, which can activate the basal plane of MoS 2. • Modifying the microscopic structures is an effective way to promote HER. MoS 2 is a classical catalyst for hydrogen evolution reaction (HER), but the performance is limited by poor electrical transport in c axis, and absent of active sites in (001) planes (basal planes). Simultaneously enhance the layer's interaction and activate the basal plane in MoS 2 is urgent. In this work, a new sight of high pressure and high temperature (HPHT) was presented to modify the microscopic structures, and finally promoting the connection among the layers and activate the basal planes in bulk MoS 2. It is found that high pressure generates shear between grains, and results stacking faults in structures. The stacking faults can enhance interaction between MoS 2 sandwich layers, and reduce the charge transfer resistance. An intermediate state was captured, which exhibits distortions in structure at 3 GPa, 200 °C. The distortions cause longer or shorter Mo-S bonds, which introduce strains to activate the basal plane. Density functional theory (DFT) calculations show that the distortions can effective reduced the adsorption free energy of H* in MoS 2 basal plane from 1.92 eV to 0.33 eV. So the activity of MoS 2 was modified by HPHT, which indicates better activity than commercial MoS 2. This work is not only significant to activate catalyst by HPHT, but also important to promote the functional materials. [ABSTRACT FROM AUTHOR]

For flexible perovskite solar cells, achieving high power conversion efficiency by using a room-temperature technology to fabricate a compact electron transport layer is one of the best options. Here, we develop an annealing-free, dopant-free, and amorphous tungsten oxide as electron transport layer by vacuum evaporation for flexible perovskite solar cells. The compact amorphous tungsten oxide electron transport layer with different thicknesses (0–50 nm) was directly deposited on flexible PEN/ITO substrate. A model of the improvement mechanism is proposed to understand how the thickness tailoring simultaneously enhances the crystallization and relaxes the trade-off between interface recombination and charge transfer. By optimizing the amorphous tungsten oxide thickness, the high homogeneous, uniform, and dense electron transport layer with a thickness of 30 nm is found to not only decrease the pinhole of the perovskite layer, but also enhance charge transport with reducing resistance. Furthermore, the mechanical bending stability revealed that, the fabricated perovskite solar cells show stable power conversion efficiency up to more than 1000 bending cycles. The room-temperature processed fabrication enables the amorphous tungsten oxide to become a potential electron transport layer candidate for the large-scale flexible perovskite solar cells, which becomes compatible with practical roll-to-roll solar cells manufacturing. Image 1 • Room-temperature and large-area a-WO x ETL has been developed for flexible PSCs. • The trade-off between charge recombination and transfer is relaxed. • Flexible PSCs based on a-WO x exhibits an excellent mechanical bending stability. • Large area a-WO x ETL achieve high efficiency for flexible perovskite solar cells. [ABSTRACT FROM AUTHOR]

Two‐photon excited chromophores are widely applied for photon upconversion in organic optoelectronics. In this work, efficient two‐photon excited fluorescence is observed from charge‐transfer cocrystals where the molecular architectures of donor and acceptor molecules are both centrosymmetric. The superior structural symmetry of cocrystals eliminates the second harmonic generation of incident near‐infrared laser. The nonlinear optical properties of cocrystals are found to be strongly correlated with the intermolecular charge‐transfer interaction, bringing a wide window of excitation wavelength for the upconverted light emission. The work demonstrates that the cocrystallization of small molecules provides opportunities for the design and synthesis of novel organic optofunctional materials. [ABSTRACT FROM AUTHOR]