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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.

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

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...

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...

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...

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.

The photoinduced intramolecular charge separation (CS) and charge recombination (CR) phenomena in a series of donor-bridge-acceptor (D-B-A) molecules are intensively investigated as a means of understanding electron transport through the π-B. Pyrene (Pyr) and triarylamine (TAA) moieties connected via phenylene Bs of various lengths are studied because their CS and CR behaviors can be readily monitored in real time by femtosecond transient absorption (fs-TA) spectroscopy. By combining the steady-state and fs-TA spectroscopic measurements in a variety of solvents together with chemical calculations, the parameters that govern the CS behaviors of these dyads were obtained, such as the solvent effects on free energy and the B-length-dependent electronic coupling (VDA) between D and A. We observed the sharp switch of the CS behavior with the increase of the solvent polarity and B-linker lengths. Furthermore, in the case of the shortest distance between D and A when the electron coupling is sufficiently large, we observed that the CS phenomenon occurs even in low-polar solvents. Upon increasing the length of B, CS occurs only in strong polar solvents. The distance-dependent decay constant of the CS rate is determined as ∼0.53 A-1, indicating that CS is governed by superexchange tunneling interactions. The CS rate constants are also approximately estimated using Marcus electron transfer theory, and the results imply that the VDA value is the key factor dominating the CS rate, while the facile rotation of the phenylene B is important for modulating the lifetime of the charge-separated state in these D-B-A dyads. These results shed light on the practical strategy for obtaining a high CS efficiency with a long-lived CS state in TAA-B-Pyr derivatives.

Transition-metal complexes (TMCs) have recently attracted considerable scientific interest for resistive memory switching. The interplay between metal ions and ligand endows TMCs with rich and tunable electrochemical and photophysical properties, making them beneficial for the formation of electrical bi- or multistates in resistive memory devices. This review summarizes the applications of TMCs in resistive memory switching. Following the simple introduction of the basic concept and switching mechanism of resistive memory devices, the recent progress on the applications of ferrocene derivatives, polyazine metal complexes and metallopolymers, alkynyl metal complexes, and porphyrin or phthalocyanine metal complexes are discussed, with an emphasis on the modulation or control of switching properties by ligand design.

A cyclometalated ruthenium sensitizer 3 containing a triphenylamine unit was synthesized and immobilized on a nanocrystalline TiO2 surface. By using oxidative electrochemical deposition, a covalent...

Sb-Doped nanocrystalline SnO2 (SnO2:Sb) thin films functionalized with cyclometalated ruthenium complexes 1 or 2 on FTO conductive glasses have been prepared and characterized. These complexes contain a redox-active amine unit separated from the ruthenium ion by a phenyl or biphenyl linker, respectively, to modify the absorption wavelengths at different redox states. Near-infrared electrochromism of both films has been examined by oxidative spectroelectrochemical measurements and double-potential-step chronoamperometry. A contrast ratio (ΔT%) of 33% at 1070 nm and 63% at 696 nm has been achieved for the SnO2:Sb/1 film in two stepwise oxidation processes, respectively. The other film with complex 2 shows two-step electrochromism at 1310 and 806 nm with ΔT% of 36% and 76%, respectively. The response time of electrochromic switching is around a few seconds. Taking advantage of the good contrast ratio, the rapid response, and the long retention time of each oxidation state, these films have been successfully used to demonstrate surface-confined flip-flop memory functions with a high ON/OFF ratio.

An IrIII-PtII heterodimetallic complex [(ppy)2Ir(dapz)PtCl2]Cl (4), together with the corresponding monometallic complexes [(dapz)PtCl2] (2) and [(ppy)2Ir(dapz)]Cl (3) was designed and prepared, where dapz is 2,5-di(N-methyl-N′-(pyrid-2-yl)amino)pyrazine and ppy is 2-phenylpyridine, respectively. Single-crystal X-ray analysis was carried out for complex 4, displaying the intermolecular Pt∙∙∙Pt and aromatic plane∙∙∙plane distances of 3.839 and 3.886 Å, respectively. The monometallic complex 2 exhibits a single emission maximum at 432 nm with a shorter excited-state lifetime (τ) of 6 ns, while complex 3 exhibits an emission band at 454 nm with a longer excited-state lifetime of 135 ns in CH3CN (N2-saturated) under ambient conditions. In contrast, the heterodimetallic complex 4 displays intriguing excitation wavelength-dependent dual singlet and triplet emissions. Theoretical calculations of the electronic structures and absorption spectra of these complexes were carried out to assist the interpretation of these experimental findings.

Molecular packing has an important effect on the photophysical properties of crystalline materials. We demonstrate in this work the modulation of molecular packing and emission properties of microcrystals by minor molecular structural variations. Four platinum β-diketonate complexes, with two fluoro substituents (

A dual-emissive tris-heteroleptic ruthenium complex is designed, synthesized and applied for the ratiometric photoluminescent detection of amyloid-β (Aβ) aggregation in both steady and transient states. The Aβ aggregation is supported by transmission electron microscopy and confocal laser scanning microscopy analysis. In addition, molecular docking calculations have been performed to gain insights into the interaction mode between the ruthenium complex and Aβ fibrils.

A pyrene-cored molecular quadripod 1,3,6,8-tetra(di(p-pyrid-4-ylphenyl)amino)pyrene (TAPyr) is presented as a noncovalent interfacial coupling reagent for the immobilization of coordination assemblies. This bench-stable molecule is readily available and has a quadripod shape with four pyridine legs and four pyridine handles on the top exterior. By a simple and short dipping procedure under ambient conditions, TAPyr is firmly immobilized on electrode surfaces in an upright fashion as probed by electrochemical, absorption spectral, atomic force microscopy, and scanning tunneling microscopy analysis. Using Pd(PhCN)2Cl2 as a metallolinker, 4-ferrocenylpyridine, a pyridine-terminated monoruthenium complex 1, and a diruthenium complex 2 with two pyridine ends have been grafted onto the ITO/TAPyr surface. The obtained thin films exhibit good electrochemical stability that is comparable or superior to those prepared by the state-of-the-art Si–O–Sn covalent functionalization. Appealing electrochromism is demonstra...

A N,N,N',N'-tetraphenylbenzidine-bridged bis(2,2'-bipyridine) ligand and corresponding diruthenium complexes were synthesized and characterized. They show rich multistep redox processes due to the stepwise oxidations of the amine units and ruthenium components. Their absorption and emission spectral changes in response to electrochemical stimulus were examined by spectroelectrochemical measurements. DFT and TDDFT calculations were performed to complement the experimental results.

Six triarylamine derivatives 1 – 6 with branched multi-pyridine substituents were prepared and characterized. These compounds are distinguished by the substituent on one of the phenyl group with NO2 for 1 , CN for 2 , Cl for 3 , p -C6H4OMe for 4 , OMe for 5 , and NMe2 for 6 , respectively. As revealed by single crystal X-ray analysis, these substituents play an important role in determining the configuration of the triarylamine framework and the crystal packing of 1 – 6 . The emission properties of these compounds were examined in different solvents (toluene, CH2Cl2, acetone, tetrahydrofuran (THF), and N , N -dimethylformamide (DMF)) and in solid states. Distinct dual emissions from the localized emissive state and the intramolecular charge transfer state were observed for compound 5 in CH2Cl2. Compounds 1 and 6 show apparent aggregated enhanced emissions in acetone/H2O. The emission properties of these compounds were further modulated by the addition of tris(pentafluorophenyl)borane. In addition, density functional theory (DFT) and time-dependent DFT (TDDFT) calculations have been performed on the ground and singlet excited states to complement the experimental findings.

As a pump for extracting carriers from the absorber to the cathode, hole transporting materials (HTMs) play indispensable roles in promoting the power conversion efficiencies (PCE) of perovskite solar cells (PSCs). In this context, we present two simple HTMs using 2,2′-(1,2-phenylene) bisthiophene or naphtho[1,2-b:4,3-b′]dithiophene as a π-bridge to link two electron-donor units (4′,4′′-dimethoxytriphenylamine): PBT and NDT. Their frontier molecular orbital energies match well with those of perovskites as is consistent with the DFT calculation results. The PCE measured under mimetic solar illumination (AM 1.5, 100 mW cm−2) increases from 13.6% (PBT) to 18.8% (NDT), which surpass that of the spiro-OMeTAD (18.1%) reference. The modified annulated core in NDT makes it perform better in photovoltaic conversion than PBT. The reason for this is discussed from aspects of hole mobility, charge collection probability (Pc) and recombination kinetics.

Four bridged cyclometalated diruthenium systems are highlighted in this Frontier article, including strongly-coupled diruthenium complexes with a short phen-1,4-diyl or a planar pyren-2,7-diyl bridge, redox asymmetric diruthenium complexes characterized by different terminal ligands on the two ends, diruthenium complexes with a urea bridge that allows modulating the degree of electronic coupling, and those with a redox-active amine bridge with varying electronic structures. These complexes posess redox couples with low potentials and intense intervalence charge transfer absorptions in the near-infrared region in the one-electron-oxidized mixed-valent state. They are appealing not only for providing a platform for fundamental electron transfer studies but also as molecular materials with multi-stage redox switching properties.

A polypyridyl monoruthenium complex with a dangling coordination site shows dual fluorescence/phosphorescence emissions at room temperature. The emission properties can be modulated by multiple stimuli including solvents, O2, and metal ions.

Two structurally asymmetric cyclometalated ruthenium complexes 3(PF6) and 4(PF6), with an amine substituent on the cyclometalating and noncyclometalating ligand of each complex respectively, have been prepared and characterized. Three consecutive anodic redox couples are observed for these complexes in the potential window of 0 ~ +1.5 V vs Ag/AgCl, assigned to the stepwise oxidations of the ruthenium component and the two amine substituents. Upon stepwise oxidations with SbCl5, these complexes exhibit three-step absorption spectral changes in the near-infrared (NIR) region. At the singly-oxidized state, single-line or axial-like EPR signals are detected for 32+ and 42+, respectively. The NIR absorptions of 3n+ and 4n+ at different charge states (n = 2 – 4) are rationalized by time-dependent density functional theory calculations.

Perovskite solar cells represent one of the most exciting developments in photovoltaics in the past decade, with the power conversion efficiencies of over 25% being achieved to date. In high-performance perovskite solar cells, hole-transporting materials are generally employed to extract and transport holes from perovskite. Among them, small molecular hole transporting materials have attracted intense interest due to their tunable energy levels, structural variety, and simple synthesis. The commonly used hole-transporting material is 2,2′,7,7′-tetrakis(N,N-di-p-methoxyphenyl amino)-9,9′-spirobifluorene (spiro-OMeTAD). Considering the high synthetic cost of spiro-OMeTAD and the device stability issue associated with the use of dopants, much research has been focused on the development of alternative high-performance hole-transporting materials. Herein, this review summarizes the recent developments in highly efficient small molecular hole-transporting materials with a power conversion efficiency close to or over 20%. On the basis of their structural features, three categories of small molecules are identified and discussed as highly efficient hole-transporting materials: spiro molecules with new terminal groups or a new spiro skeleton, star-shaped small molecular hole-transporting materials with three or four branches, and linear hole-transporting materials with a D-A, D-π-D, D-A-D, or D-A-π-A-D structure. The relationships of the optoelectronic properties of these hole-transporting materials and the device performance are discussed, with a comparison to those of model compounds in some cases. Finally, an outlook is addressed on the future development of hole-transporting materials for high-performance perovskite solar cells. We hope that this review can provide important guidance for the design and synthesis of new hole-transporting materials and finally help to promote the commercialization of perovskite solar cells.

Two bis-tridentate pincer complexes [Ru(H 2 bip)(Mebib)](PF 6 ) 2 ( 1 (PF 6 ) 2 ) and [Ru(H 2 bip)(H 2 bib)](PF 6 ) 2 ( 2 (PF 6 ) 2 ) were prepared and studied, where H 2 bip is 2,6-bis(benzimidazol-2-yl)pyridine, Mebib is the 2-deprotonated 1,3-bis( N -methylbenzimidazol-2-yl)benzene, and H 2 bib is 2-deprotonated 1,3-bis(benzimidazol-2-yl)benzene. These complexes were isolated as cyclometalated Ru(III) salts with a [(NCN)(NNN)] coordination due to a low Ru(III/II) redox potential. Complex 1 (PF 6 ) 2 has two N−H protons on the NNN ligand side, while complex 2 (PF 6 ) 2 has four N−H protons. Absorption spectral analysis showed that two deprotonation steps were distinguished for 1 (PF 6 ) 2 with p K a1 and p K a2 of 3.46 and 5.88, respectively. In comparison, four deprotonation steps were observed for 2 (PF 6 ) 2 with four p K a values of 3.45, 5.95, 8.95, and 10.98, respectively. When the solution was changed from acidic to basic, the Ru(III/II) redox wave of 1 (PF 6 ) 2 and 2 (PF 6 ) 2 shifted from +0.20 V vs Ag/AgCl to a less positive region by 540 and 850 mV, respectively. These studies suggest that the electronic absorption and electrochemical properties of these complexes are very sensitive to pH effect.

Three tris-bidentate monoruthenium complexes [Ru(dpma)(bpy)2](PF6)2 (1(PF6)2, dpma = di(pyrid-2-yl)-methylamine; bpy = 2,2′-bipyridine), [Ru(dpma)2(bpy)](PF6)2 (2(PF6)2), and [Ru(dpma)3](PF6)2 (3(PF6)2) with the electron-rich ligand dpma were synthesized and characterized. The single-crystal X-ray structures of 1(PF6)2 - 3(PF6)2 are presented. The electrochemical and spectroscopic properties of these complexes were examined and compared with those of the reference complex [Ru(bpy)3](PF6)2. Complexes 1(PF6)2 - 3(PF6)2 show a decreased Ru(III/II) redox potential by 140 - 310 mV with respect to [Ru(bpy)3](PF6)2. The strong emission property of [Ru(bpy)3](PF6)2 is maintained in 1(PF6)2 and 2(PF6)2. However, complex 3(PF6)2 is only weakly emissive at room temperature. In addition, density functional theory (DFT) and time-dependent DFT calculations were performed to complement these experimental results

Organometallic conjugated complexes have become an important type of stimuli-responsive materials because of their appealing electrochemical properties and rich photonic, electronic, and magnetic properties. They are potentially useful in a wide range of applications such as molecular wires, molecular switches, molecular machines, molecular memory, and optoelectronic detections. This review outlines the recent progress on the molecular design of carbometalated ruthenium and osmium complexes and their applications as redox-responsive materials with visible and near-infrared (NIR) absorptions and electron paramagnetic resonance as readout signals. Three molecule systems are introduced, including the symmetric diruthenium complexes, metal-amine conjugated bi-center system, and multi-center redox-active organometallic compounds. Because of the presence of a metal-carbon bond on each metal component and strong electronic coupling between redox sites, these compounds display multiple reversible redox processes at low potentials and each redox state possesses significantly different physical and chemical properties. Using electrochemical potentials as input signals, these materials show reversible NIR absorption spectral changes, making them potentially useful in NIR electrochromism and information storage.

A new small molecular hole-transporting material, 1,3,6,8-tetrakis[N-(p-methoxyphenyl)-N′-(9,9′-dimethyl-9H-fluoren-2-yl)-amino]pyrene (TFAP) was synthesized and applied in CH3NH3PbI3-perovskite solar cells. A best power conversion efficiency of 19.7% with a photovoltage of 1.11 V has been achieved.

Two star-shaped multi-triphenylamine derivatives 1 and 2 were prepared, where 2 has an additional phenyl unit between a pyrene core and surrounding triphenylamine units. The oxidative electropolymerization of 1 and 2 occurred smoothly to give thin films of polymers P1 and P2. The electrochemistry and spectroelectrochemistry of P1 and P2 were examined, showing two-step absorption spectral changes in the near-infrared region. The electrochromic properties, including contrast ratio, response time, and cyclic stability of P1 and P2 were investigated and compared. Thin film of P2 displays slightly better electrochromic performance than P1, with a contrast ratio of 45% at 1475 nm being achieved.