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CPL-active microspheres and microcrystals are fabricated via the reaction and co-assembly of pyridine derivatives with a chiral phosphoric acid.

Organic dyes with pyridine anchors are used to construct stable photoelectrochemical cells for visible-light-sensitized water reduction into H2.

Electropolymerized Zn-porphyrin films are used to fabricate the dopant-free hole-transporting layer for high-performance perovskite solar cells.

A synthetic approach to dibenzo[f,h]quinolines and their derivatives via stepwise ruthenium-catalyzed C–H arylation and potassium-mediated reductive cyclodehydrogenation from 2-phenylpyridine and aryl bromides, is presented. One dibenzo[f,h]quinoline derivative is used as a bidentate ligand to prepare a cyclometalated ruthenium complex. Two dibenzo[f,h]quinoline compounds and the ruthenium complex were characterized by single-crystal X-ray structural analysis.

Singlet fission (SF) has drawn tremendous attention as a multiexciton generation process that could mitigate the thermal loss and boost the efficiency of solar energy conversion. Although a SF-based solar cell with an EQE above 100% has already been fabricated successfully, the practical efficiency of the corresponding devices is plagued by the limited scope of SF materials. Therefore, it is of great importance to design and develop new SF-capable compounds aiming at practical device application. In the current contribution

The research in circularly polarized luminescence has attracted wide interest in recent years. Efforts on one side are directed toward the development of chiral materials with both high luminescence efficiency and dissymmetry factors, and on the other side, are focused on the exploitations of these materials in optoelectronic applications. This review summarizes the recent frontiers (mostly within five years) in the research in circularly polarized luminescence, including the development of chiral emissive materials based on organic small molecules, compounds with aggregation-induced emissions, supramolecular assemblies, liquid crystals and liquids, polymers, metal-ligand coordination complexes and assemblies, metal clusters, inorganic nanomaterials, and photon upconversion systems. In addition, recent applications of related materials in organic light-emitting devices, circularly polarized light detectors, and organic lasers and displays are also discussed.

Three tris-heteroleptic mononuclear Ru(II) complexes with dual fluorescence and phosphorescence-[Ru(dpma)(bpy)(phen)]2+ (12+), [Ru(dpma)(bpy)(dppz)]2+ (22+), and [Ru(dpma)(phen)(dppz)]2+ (32+)-have been designed and used as ratiometric light-response probes for DNA, where dpma is di(pyrid-2-yl)(methyl)-amine, bpy is 2,2'-bipyridine, phen is 1,10-phenanthroline, and dppz is dipyridophenazine, respectively. Single crystals of complex 2(PF6)2 have been obtained and studied by X-ray analysis. The interactions of these complexes with different DNAs are investigated by means of spectroscopic methods, viscosity measurements, and molecular modeling. In the presence of calf thymus DNA, complexes 2(PF6)2 and 3(PF6)2 show the emergence of a new lower-energy phosphorescence emission band; meanwhile, the higher-energy fluorescence emission band is essentially unchanged, functioning as an intrinsic internal reference. These two complexes exhibit stronger preference for calf thymus DNA over single-strand DNA (d(A)16 and d(C)16). In contrast, no binding interaction between 1(PF6)2 and calf thymus DNA is observed. The intrinsic binding constants (Kb) of 2(PF6)2 and 3(PF6)2 with calf thymus DNA are determined to be (1.4 ± 0.4) × 105 and (9.5 ± 0.15) × 104 M-1, respectively. In addition, these spectroscopic results are compared with those of the prototype complex [Ru(bpy)2(dppz)]2+ (42+), and density functional theory and time-dependent density functional theory calculations are employed to elucidate these experimental findings.

Inorganic cesium lead halide perovskites offer a pathway towards thermally stable photovoltaics. However, moisture-induced phase degradation restricts the application of hole transport layers (HTLs) with hygroscopic dopants. Dopant-free HTLs fail to realize efficient photovoltaics due to severe electrical loss. Herein, we developed an electrical loss management strategy by manipulating poly(3-hexylthiophene) with a small molecule, i.e., SMe-TATPyr. The developed P3HT/SMe-TATPyr HTL shows a three-time increase of carrier mobility owing to breaking the long-range ordering of "edge-on" P3HT and inducing the formation of "face-on" clusters, over 50 % decrease of the perovskite surface defect density, and a reduced voltage loss at the perovskite/HTL interface because of favorable energy level alignment. The CsPbI2 Br perovskite solar cell demonstrates a record-high efficiency of 16.93 % for dopant-free HTL, and superior moisture and thermal stability by maintaining 96 % efficiency at low-humidity condition (10-25 % R. H.) for 1500 hours and over 95 % efficiency after annealing at 85 °C for 1000 hours.

In this work, we present a series of donor–acceptor–donor type of small molecules (BDAD, ODAD, and DDAD) based on the triphenylamine (TPA) and dithienopyrrolobenzothiadiazole (DTPBT) units, which a...

A Kagome structure covalent organic framework (COF) film with three-state near-infrared (NIR) electrochromic properties was designed and synthesized. The morphology and structure characterization revealed that the COFTPDA-PDA film was composed of hexagonal nanosheets with high crystallinity. The COFTPDA-PDA film exhibit three reversible color states at different applied potentials, and high absorption spectra changes in the NIR region, which can be ascribed to the strong intervalence charge transfer (IVCT) interaction of the Class III mixed-valence systems of the conjugated triphenylamine species. The COFTPDA-PDA film showed the sub-second response time (1.3 s for coloring and 0.7 s for bleaching at 1050 nm) and the long retention time in the NIR region. In comparison with the amorphous film with the same monomers, COFTPDA-PDA film show superior NIR electrochromic properties in term of response time and stability, which could be attributed to the highly ordered porous structure and the π-π stacking structure of the COFTPDA-PDA architecture. Furthermore, the COFTPDA-PDA film was successfully applied in mimicking flip-flop logic gate with optical memory functions.

The use of hole-transporting materials (HTMs) is crucial in achieving high photovoltaic performance in perovskite solar cells (PSCs). Considering the high-cost, difficult synthesis, and/or the devi...

A new class of high-quality ionic organic microcrystals with bright deep-blue luminescence (with up to 60% quantum yield) have been prepared in situ by the protonation of 2,2′-di(pyrid-2-yl)bipheny...

Eight nonplanar terdentate cyclometalated Pt(II) complexes (Pt1–Pt8) have been designed and synthesized with the general formula [Pt(N∧C∧N)Cl], where N∧C∧N represents 1,3-bis(N-methyl-N′-(pyridin-2...

Circularly polarized luminescence (CPL) materials have potential applications in three-dimensional (3D) displays, quantum encryption, and optical sensors. The development of single-component CPL materials with polymorphic assembly and handedness inversion remains a significant challenge. Herein, we present the access of such materials by controlling the underlying assembly pathway of well-designed chiral emitters. A pair of enantiomeric platinum complexes (R)-1 and (S)-1 decorated with a chiral α-methylbenzyl isocyanide ligand were prepared. By using the mixed-solvent (THF/n-hexane, THF=tetrahydrofuran) or high-concentration condition, these complexes were found to assemble via a cooperative or isodesmic pathway with significantly enhanced yellow or red emission, respectively. The aggregate samples obtained via these conditions show efficient CPL (dissymmery factor ∣glum∣>0.02, emission quantum yield Φ>20%). Interestingly, different assembly pathway leads to helical nanoribbons or nanofibers with opposite handedness from the complex with the same molecular chirality. This has been unambiguously and consistently manifested by circular dichroism and CPL spectral analysis and transmission electron, scanning electron, and atomic force microscope studies. This work demonstrates an appealing example of constructing polymorphic helical architectures with highly efficient CPL and inverted handedness thanks to the excellent assembly and emission of platinum complexes.

In this work, a new small molecular material, 9,9'-(pyrene-1,6-diyldimethylylidene)bis[N,N,N′,N′-tetrakis(4-methoxyphenyl)-9H-fluorene-2,7-diamine] (PFD), as a hole-transporting layer was designed for perovskite solar cells (PSCs). PFD has a rigid and flat pyrene unit as the central building block and a symmetric structure to increase the conjugation degree for better carrier conductivity. A power conversion efficiency (PCE) of 18.6% was achieved for PSC based on undoped PFD. When spiro-OMeTAD is further introduced on the top of PFD (PFD/spiro-OMeTAD), a PCE of 21.02% was achieved with a steady-state efficiency of 19.92%, revealing that PFD as an interfacial layer could restrain carrier recombination. Unencapsulated devices based on PFD or PFD/spiro-OMeTAD exhibit excellent stability including long-term stability for over 1400 h under ambient condition, and moisture stability under the “Double 60 program” test simultaneously at 60% RH and 60 °C in air. Besides, no obvious degradation was found for the PFD/spiro-OMeTAD device over 200 h under continuous illumination at the maximum power point tracking (MPPT) in N2 atmosphere. It is thus suggested that PFD could be a promising dopant-free HTM for PSCs, and also acts as an interface layer to suppress the carrier recombination to further improve the device performance.

Three cyclometalated diruthenium complexes bridged by 3,3',5,5'-tetrakis(benzimidazol-2-yl)biphenyl (H-tbibp) and capped with different terminal ligands have been synthesized and examined. In addition, two monoruthenium complexes with H-tbibp have been prepared for the purpose of comparison studies. The degree of Ru-Ru electronic coupling of these diruthenium complexes has been investigated by electrochemical and intervalence charge-transfer (IVCT) analyses. These results suggest that when the same or similar terminal ligands are used, the strength of H-tbibp in mediating the Ru-Ru coupling is enhanced with respect to that of the previously reported bridging ligand 3,3',5,5'-tetrakis(N-methylbenzimidazol-2-yl)biphenyl, but it is slightly inferior to that of the classical bridging ligand 3,3',5,5'-tetrakis(pyrid-2-yl)biphenyl. This trend is also supported by CNS analyses based on the hole-superexchange mechanism. In addition, DFT calculations have been performed to probe the spin density distributions of the singly-oxidized diruthenium complexes with H-tbibp and TDDFT calculations are used to reproduce the IVCT transitions.

Electrochemiluminescence (ECL) of crystalline materials has recently attracted increasing attention due to their unique characteristics and applications, such as crystallization-induced emission, active waveguiding, and biosensing. Tris(2,2′-bipyridine)ruthenium(II), [Ru(bpy)3]2+, a classical metal–organic complex for ECL studies, has been fully investigated in solution as well as its derivatives. However, the dependence of ECL properties on the molecular structure and crystal morphology of these complexes has not been illustrated, partially due to the difficulty in the controlled crystal growth. Here, we adopt a facile molecular engineering strategy to obtain microcrystals of [Ru(bpy)3]2+ derivatives with well-defined morphology (rods, wires, or polyhedrons) and varied phosphorescence emission colors (yellow, orange, and red) by simply changing the position and number of methyl substituents on the bipyridine ligands. The packing modes of molecules influenced by methyl groups play a vital role in crystal growth based on attachment energy analysis. The obtained microcrystals could act as ECL luminophores when modified on glassy carbon electrode surfaces. Those with one-dimensional (1D) morphology generally show superior ECL efficiency and stability to three-dimensional (3D) shaped microcrystals. ECL biosensors made of stable 1D microcrystals show reliable and sensitive responses to hydroxyproline, demonstrating their capacity in recyclable detections. This work demonstrates the great potential of molecular engineering in controlling the morphology, emission colors, and ECL properties of molecular crystals, paving the way for the development of high-performance ECL biosensing and optoelectronic devices.

Currently, there is an urgent need to develop low-cost hole-transporting materials (HTMs) for inverted perovskite solar cells (PSCs), whose power conversion efficiency (PCE) is still inferior to th...

Singlet oxygen (1O2), as an important active reagent, has found wide applications in photodynamic therapy (PDT), synthetic chemistry, and materials science. Organic conjugated aromatics serving as hosts to capture and release singlet oxygen have been systematically investigated over the last decades. Herein, we present a [6 + 6] organoplatinum(II) metallacycle by using ∼180° dipyridylanthracene donor and ∼120° Pt(II) acceptor as the building blocks, which enables the capture and release of singlet oxygen with relatively high photooxygenation and thermolysis rate constants. The photooxygenation of the metallacycle to the corresponding endoperoxide was performed by sensitized irradiation, and the resulting endoperoxide is stable at room temperature and can be stored under ambient condition over months. Upon simple heating of the neat endoperoxide under inert atmosphere at 120 °C for 4 h, the resulting endoperoxide can be reconverted to the corresponding parent form and singlet oxygen. The photooxygenation and thermolysis products were characterized by NMR spectroscopy and electrospray ionization time-of-flight mass spectrometric analysis. Density functional theory calculations were conducted in order to reveal the frontier molecular orbital interactions and reactivity. This work provides a new material platform for singlet oxygen related promising applications.

Dual-emissive transition-metal complexes can display two emission bands at distinctly different wavelength. They have the double advantages of being dual-emissive materials and photofunctional transition-metal complexes. They are useful in a wide range of applications such as ratiometric photoluminescent probes and bio-imaging. Compared to metal complexes with a single emission band, ratiometric photoluminescent probes based on dual-emissive complexes could effectively decrease the influence induced by the fluctuation of excitation energy and environment effects, and thus improve the sensitivity and accuracy. This review briefly summarizes the design strategies for the synthesis of dual-emissive transition-metal complexes, in particular ruthenium, iridium, and platinum complexes, and their applications as ratiometric photoluminescent probes. In addition, the current challenges in the studies of dual-emissive transition-metal complexes are discussed, which is of interest and importance to the synthesis and applications of new dual-emissive molecular materials in the future.

Lithium-ion batteries (LIBs) have been demonstrated as one of the most promising energy storage devices for applications in electric vehicles, smart grids, large-scale energy storage systems, and portable electronics. Compared with traditional inorganic compounds that often cause various environmental problems, organic electrode materials possess many advantages, such as the diversity of molecular structures, feasibility of subjective design, light weight, low cost, high theoretical capacity, and eco-friendliness, making them very promising in the application of energy-related devices. Among all organic materials used as electrodes for LIBs, organic carbonyl-based polymers with multi-electron reaction centers, high theoretical capacity, reaction reversibility, rapid redox kinetics, and the inhibition of electrolyte dissolution have recently become hot topics. In this review, we summarize the recent progress in the design, synthesis, and application of carbonyl-based polymers for LIBs. In addition, the advantages/disadvantages of individual materials are also discussed.

Conventional square-planar platinum complexes typically form one-dimensional assemblies as a result of unidirectional metallophilic and/or π⋅⋅⋅π intermolecular interactions. Organoplatinum(II) complexes with a cruciform shape are presented herein to construct two-dimensional (2D) microcrystals with full-color and white phosphorescence. These 2D crystals show unique monocomponent π⋅⋅⋅π stacking, from either the cyclometalating or noncyclometalating ligand, and the bicomponent alternate π⋅⋅⋅π stacking from both ligands along different facet directions. Anisotropic tri-directional waveguiding is further implemented on a single hexagonal microcrystal. These results demonstrate the great capability of the organoplatinum(II) cruciform as a general platform to fabricate 2D phosphorescent micro-/nanocrystals for advanced photonic applications.