Regulating Crystallization and Lead Leakage of Perovskite Solar Cell Via Novel Polyoxometalate-Based Metal-Organic Framework.

Despite the unprecedented progress in lead-based perovskite solar cells (PSCs), the toxicity and leakage of lead from degraded PSCs triggered by deep-level defects and poor crystallization quality increase environmental risk and become a critical challenge for eco-friendly PSCs. Here, a novel 2D polyoxometalate (POM)-based metal-organic framework (MOF) (C5 NH5 )4 (C3 N2 H5 )2 Zn3 (H8 P4 Mo6 O31 )2 ·2H2 O (POMOF) is ingeniously devised to address these issues. Note that the integration of POM endows POMOF with great advantages of electrical conductivity and charge mobility. Ordered POMOF induces the crystallization of high-quality perovskite film and eliminates lead-based defects to improve internal stability. The resultant PSCs achieve a superior power conversion efficiency (23.3%) accompanied by improved stability that maintains ≈90% of its original efficiency after 1600 h. Meanwhile, POMOF with phosphate groups effectively prevents lead leakage through in situ chemical anchoring and adsorption methods to reduce environmental risk. This work provides an effective strategy to minimize lead-based defects and leakage in sustainable PSCs through multi-functional POM-based MOF material.

Multilateral Passivation Strategy in Post-Synthetic Flexible Metal-Organic Frameworks for Enhancing Perovskite Solar Cells.

The photovoltaic performance of perovskite solar cells is severely limited by the innate defects of perovskite films. Metal-organic framework (MOF)-based additives with luxuriant skeleton structures and tailored functional groups show a huge potential to solve these problems. Here, a multilateral passivation strategy is performed by introducing two alkyl-sulfonic acid functionalized MOFs, MIL-88B-1,3-SO3H and MIL-88B-1,4-SO3H, respectively, obtained from MIL-88B-NH2 through a post-synthetic process, for coordinating the lead defects and inhibiting non-radiative recombination. The flexible MIL-88B-type frameworks endow both functionalized MOFs with excellent electrical conductivity and preferable carrier transport in the hole-transport materials. Compared with the original MIL-88B-NH2 and MIL-88B-1,4-SO3H, MIL-88B-1,3-SO3H exhibits optimal steric hindrance and multiple passivation groups (-NH2, -NH-, and -SO3H), achieving the champion doped device with an enhanced power conversion efficiency (PCE) of 22.44% and excellent stability, which maintains 92.8% of the original PCE under ambient conditions (40% humidity and 25 °C) for 1200 h.

{Mo126 W30 }: Polyoxometalate Cages Shaped by π-π Interactions.

Here we report the formation of giant {Mo126 W30 } polyoxometalate cages templated by π-conjugated planar ligands. Their inorganic shells incorporate arrays of 18 stacked aromatic carboxylates, such as 1,3,5-benzenetricarboxylate or 5-nitroisophthalate, and the assembly is stabilized by multiple π-π interactions. NMR data confirmed that the cages are stable in solution and the inner aromatic templates can be postsynthetically replaced by selected aliphatic dicarboxylates, paving the way for endo-functionalization and exploration of the reactivities within the cage cavities.

Sulfur-Containing Bent N-Heteroacenes.

A series of novel sulfur-containing bent N-heteroacenes were constructed and characterized by NMR and UV/Vis spectroscopy, cyclic voltammetry, and single-crystal X-ray diffraction. By introducing sulfur-containing groups (thio, sulfinyl, and sulfonyl) into bent azaacenes, their electronic delocalization was improved and frontier energy levels were modulated. The target products displayed tunable optical and electronic properties through altering the valence of sulfur and fused length of the azaacenes. For the first time, typical products were utilized as organic field effect transistor materials, affording promising results.

Synthesis of π-Conjugated Benzocyclotrimers.

Polycyclic aromatic hydrocarbons (PAHs), especially three branchphene benzocyclotrimers represent a series of molecules with intriguing physical and chemical properties. Benzocyclotrimers are also important precursors to construct fullerenes and graphenes. In this article, we review the recent progress in the preparation methods of π-conjugated benzocyclotrimers. In particular, cyclotrimerization reactions to construct varying shaped and edged benzocyclotrimers are illustrated. Various typical characterization methods for these materials, such as variable-temperature 1 H-NMR, single crystal X-ray analysis, density functional theory (DFT) calculations and atomic force microscope (AFM) measurements are included for discussion.

Hydrodynamic Analysis-Based Modeling and Experimental Verification of a New Water-Jet Thruster for an Amphibious Spherical Robot.

Thrusters are the bottom actuators of the amphibious spherical robot, and play an important role in the motion control of these robots. To realize accurate motion control, a thrust model for a new water-jet thruster based on hydrodynamic analyses is proposed in this paper. First, the hydrodynamic characteristics of the new thruster were numerically analyzed using computational fluid dynamics (CFD) commercial software CFX. The moving reference frame (MRF) technique was utilized to simulate propeller rotation. In particular, the hydrodynamics of the thruster were studied not only in the axial flow but also in oblique flow. Then, the basic framework of the thrust model was built according to hydromechanics theory. Parameters in the basic framework were identified through the results of the hydrodynamic simulation. Finally, a series of relevant experiments were conducted to verify the accuracy of the thrust model. These proved that the thrust model-based simulation results agreed well with the experimental results. The maximum error between the experimental results and simulation results was only 7%, which indicates that the thrust model is precise enough to be utilized in the motion control of amphibious spherical robots.

Self-Assembly of Hybrid Oxidant POM@Cu-BTC for Enhanced Efficiency and Long-Term Stability of Perovskite Solar Cells.

The controllable oxidation of spiro-OMeTAD and improving the stability of hole-transport materials (HTMs) layer are crucial for good performance and stability of perovskite solar cells (PSCs). Herein, we report an efficient hybrid polyoxometalate@metal-organic framework (POM@MOF) material, [Cu2 (BTC)4/3 (H2 O)2 ]6 [H3 PMo12 O40 ]2 or POM@Cu-BTC, for the oxidation of spiro-OMeTAD with Li-TFSI and TBP. When POM@Cu-BTC is introduced to the HTM layer as a dopant, the PSCs achieve a superior fill factor of 0.80 and enhanced power conversion efficiency 21.44 %, as well as improved long-term stability in an ambient atmosphere without encapsulation. The enhanced performance is attributed to the oxidation activity of POM anions and solid-state nanoparticles. Therefore, this research presents a facile way by using hybrid porous materials to accelerate oxidation of spiro-OMeTAD, further improving the efficiency and stability of PSCs.

Layered Electron Acceptors by Dimerization of Acenes End- Capped with 1,2,5-Thiadiazoles.

Layered electron acceptors D1-4 equipped with terminal 1,2,5-thiadiazole groups have been constructed using a one-pot protocol of acene dimerization. Their molecular structures are determined using single-crystal X-ray diffraction analysis. Photophysical and electrochemical properties of these molecules present a marked dependence on conjugation length and molecular geometry. An aggregation-induced emission peak and an intramolecular excimer emission (IEE) band were observed for D2 and D4, respectively. This work paves the way for the efficient synthesis of layered heteroacenes.

Self-host blue-emitting iridium dendrimer with carbazole dendrons: nondoped phosphorescent organic light-emitting diodes.

A blue-emitting iridium dendrimer, namely B-G2, has been successfully designed and synthesized with a secondgeneration oligocarbazole as the dendron, which is covalently attached to the emissive tris[2-(2,4-difluorophenyl)-pyridyl]iridium(III) core through a nonconjugated link to form an efficient self-host system in one dendrimer. Unlike small molecular phosphors and other phosphorescent dendrimers, B-G2 shows a continuous enhancement in the device efficiency with increasing doping concentration. When using neat B-G2 as the emitting layer, the nondoped device is achieved without loss in efficiency, thus giving a state-of-art EQE as high as 15.3% (31.3 cdA1, 28.9 lmW1) along with CIE coordinates of (0.16, 0.29).

Molecular near-infrared triplet-triplet annihilation upconversion with eigen oxygen immunity.

Molecular triplet-triplet annihilation upconversion often experiences drastic luminescence quenching in the presence of oxygen molecules, posing a significant constraint on practical use in aerated conditions. We present an oxygen-immune near-infrared triplet-triplet annihilation upconversion system utilizing non-organometallic cyanine sensitizers (λex = 808 nm) and chemically synthesized benzo[4,5]thieno[2,3-b][1,2,5]thiadiazolo[3,4-g]quinoxaline dyes with a defined dimer structure as annihilators (λem = 650 nm). This system exhibits ultrastable upconversion under continuous laser irradiance (>480 mins) or extended storage (>7 days) in aerated solutions. Mechanistic investigations reveal rapid triplet-triplet energy transfer from sensitizer to annihilators, accompanied by remarkably low triplet oxygen quenching efficiencies ( η O 2 < 13% for the sensitizer, <3.7% for the annihilator), endowing the bicomponent triplet-triplet annihilation system with inherent oxygen immunity. Our findings unlock the direct and potent utilization of triplet-triplet annihilation upconversion systems in real-world applications, demonstrated by the extended and sensitive nanosensing of peroxynitrite radicals in the liver under in vivo nitrosative stress.