Thermally Stable D2h Symmetric Donor-π-Donor Porphyrins as Hole-Transporting Materials for Perovskite Solar Cells.

A series of new D2h symmetric porphyrins (MDA4, MTA4, and MDA8) with donor-π-donor structures have been synthesized as the hole-transporting materials for perovskite solar cells (PSCs). The novel porphyrin molecules feature a D2h symmetrically substituted ZnII porphyrin core and two kinds of donor systems (diarylamine (DAA) and triarylamine (TAA)), which can regulate energy level, increase thermal stability, solubility, and hydrophobicity via long alkoxyl chains. PSC devices based on MDA4 as the HTM showed impressive power-conversion efficiency (PCE) of 22.67 % under AM1.5G solar illumination. Notably, the device was sent for certification, and a PCE of 22.19 % was reported, representing the highest PCE from porphyrin-based HTMs. Furthermore, the MDA4-based PSCs showed excellent thermal stability under 60 °C and RH 60 % and preserved 88 % of initial performance after 360 hours. The strategy opens a new avenue for developing efficient and stable porphyrin HTMs for PSCs.

Effect of the Steric Hindrance and Branched Substituents on Visible Phenylamine Oxime Ester Photoinitiators: Photopolymerization Kinetics Investigation through Photo-DSC Experiments.

In this work, free radical photopolymerization (FRP) kinetics for series of different phenylamine oxime ester structures (DMA-P, DEA-P, DMA-M, TP-2P, TP-2M and TP-3M) was investigated. Steric hindrance and branched substituents were prepared to realize the corresponding electronic and photopolymerization effects. The photophysical, electrochemical, thermal properties and radical concentration were investigated by UV-visible spectroscopy, cyclic voltammetry (CV), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and electron paramagnetic resonance (EPR). Furthermore, the structure-reactivity relationships were also studied in detail through photo-DSC experiment. We demonstrate that the introduction of alkyl chains and/or numbers of oxime esters affects significantly the photoreactivity. Under the same weight ratio of formulation and irradiated condition, TP-3M containing three oxime esters in its structure and methyl group in the periphery exhibits the highest double-bond conversion efficiency. TP-3M-based formulation also shows a wide operation window under different contents and light intensities. Importantly, the photoreactivity of the TP-3M-based system was found to be better than the commercial photoinitiator (OXE-01) under LED@405 nm at a low concentration. This work could provide some significance to the design of oxime esters with enhanced photoreactivity.

Double Fence Porphyrins that are Compatible with Cobalt(II/III) Electrolyte for High-Efficiency Dye-Sensitized Solar Cells.

A series of new double fence porphyrin dyes bJS1-bJS3, with eight long alkoxyl chains attached to four ß-phenyl groups, have been designed and synthesized. The single fence meso-substituted counterparts mJS1-mJS3 were also prepared as reference dyes. Dyes bJS1-bJS3 and mJS1-mJS3 exhibit power conversion efficiencies of 8.03-10.69 % and 2.33-6.69 %, respectively. Based on photovoltaic studies, the remarkable cell performance of double fence porphyrin sensitizers can be attributed to reduced dye aggregation and a decreased charge-recombination rate. Notably, porphyrins bJS2 and bJS3 exhibit better efficiency than the benchmark YD2-o-C8 (9.83 % in this work), demonstrating that the double fence structure is a promising design strategy for efficient porphyrin sensitizers in high-performance DSSCs.

tert-Butylpyridine Coordination with [Cu(dmp)2]2+/+ Redox Couple and Its Connection to the Stability of the Dye-Sensitized Solar Cell.

Cu(I)/(II) complex redox couples in dye-sensitized solar cell (DSSC) are of particular interest because of their low reorganization energy between Cu(I) and Cu(II), which minimizes the potential loss during sensitizer regeneration, thus allowing the open-circuit voltage of the device to go over 1.0 V. However, Cu(I)/(II)-based redox couples are reported to coordinate with 4-tert-butylpyridine (TBP), which is a standard additive in the electrolyte, and this is believed to account for the poor durability of a Cu(I)/(II)-based DSSCs. Despite TBP coordination on Cu(I)/(II) complexes are confirmed in the literature, its detailed mechanism is yet to be directly proven. In addition, how TBP coordination with Cu(I)/(II) complexes affects the stability of the device is never reported. Here, we choose bis(2,9-dimethyl-1,10-phenanthroline) copper(I)/(II) ([Cu(dmp)22+/+]) as the modeling redox couple to investigate its interaction with TBP. It is found that [Cu(dmp)2+] is resistive to TBP coordination but could form three new TBP-coordinated compounds. Moreover, it is also confirmed their electrochemical activity on Pt catalyst and mass transfer capability are both demoted significantly. As a result, serious fill factor loss is observed on the stability trail while short-circuit current density and open-circuit voltage are relatively unaffected. This unique degradation pattern may resemble a feature of Cu(I)/(II)-based redox couple after TBP poisoning.

Assessment of the intramolecular magnetic interactions in the highly saddled iron(iii) porphyrin π-radical cations: the change from planar to saddle conformations.

The intramolecular magnetic interactions in one-electron oxidized iron(iii) porphyrin π-radical cations, [Fe(OETPP˙)Cl][SbCl6] (1), [Fe(OMTPP˙)Cl][SbCl6] (2) and [Fe(TPP˙)Cl][SbCl6] (3), have been compared by means of X-ray crystallography, SQUID magnetometry, cyclic voltammetry, UV-Vis spectroelectrochemical analysis, NMR spectroscopy analysis and unrestricted DFT calculations. Unlike a generally recognized antiferromagnetic coupling dxy↑dxz↑dyz↑dz2↑dx2-y2↑P˙+(a2u)↓ (S = 2) state via a weak bonding interaction as in (3), we have disclosed that a strong bonding interaction among iron dx2-y2 and porphyrin a2u orbitals forms in (1) into a highly delocalized Ψπ = [P˙+(a2u) + FeIII(dx2-y2, dz2)] orbital that is able to accommodate two spin-paired electrons to form the Ψπ2dxy1dxz1dyz1, dz21 (S = 2) ground state. Concurrently, the spin polarization effect is exerted on the paired spins in the Ψπ orbital by magnetic induction from the remaining unpaired electrons in the iron d orbitals. The interpretation mentioned above is further verified by the diamagnetic nature of the saddled copper(ii) porphyrin π-cation radical, CuII(OETPP˙)(ClO4) (S = 0), where the strong bonding interaction leads to the Ψπ2dxy2dxz2dyz2dz22 (S = 0) ground state but no spin polarization exists. Thus, the magnetic nature of the iron(iii) porphyrin π-radical cation is tuneable by saddling the ring planarity.

Evaluation of Efficacy and Toxicity of Exfoliated Silicate Nanoclays as a Feed Additive for Fumonisin Detoxification.

The efficacy of nanosilicate clay platelets (NSCP), exfoliated silicates from natural montmorillonites, as a feed additive for ameliorating fumonisin B1 (FB1) toxicosis was evaluated. Toxicological mechanisms by NSCP were examined through proteomic and biochemical analyses. Dietary supplementation with NSCP at a low level of 40 mg/kg of feed improved growth performances in chickens with respect to FB1 toxicosis. Other issues of ameliorated symptoms including serum and/or hepatic aspartate aminotransferase activity, oxidative stress indicators, and sphinganine/sphingosine ratio, a hallmark of FB1 toxicosis, were considered. Chickens with NSCP inclusion alone at 1000 mg/kg of feed exhibited no changes in hepatic histology, oxidative status, and serum parameters and even had a higher feed intake. Proteomic analysis with liver tissues identified 45 distinct proteins differentially affected by FB1 and/or NSCP, in which proteins involved in thiol metabolism and redox regulation, glycolysis, carcinogenesis, and detoxification by glutathione S-transferase were promoted by FB1, whereas NSCP caused differential changes of protein abundances related to methionine/cysteine and choline/glycine interconversion for glutathione synthesis, redox regulation by peroxiredoxin, toxin/metabolite delivery by albumin, glycolysis, tricarboxylic acid cycle, adenosine triphosphate (ATP) synthesis, and chaperon escort for endoplasmic reticulum stress relief. Functional analyses confirmed the enhancement of hepatic metabolic processes for ATP and NAD(P)H production to meet the need for detoxification, antioxidative defense, and toxin/metabolite clearance by FB1 or NSCP ingestion. On the basis of the amelioration of FB1 toxicosis, global profile of hepatic protein expressions, and validated toxicological mechanisms, NSCP were concluded as a safe and effective agent for FB1 detoxification.

Linear oligoarylamines: electrochemical, EPR, and computational studies of their oxidative states.

A series of straight-chain oligoarylamines were synthesized and examined by electrochemical, spectroelectrochemical, electron paramagnetic resonance techniques, and density functional theory (DFT) calculation. Depending on their electrochemical characteristics, these oligoarylamines were classified into two groups: one containing an odd number and the other an even number of redox centers. In the systems with odd redox centers (N1, N3, and N5), each oxidation was associated with the loss of one electron. As for the systems with even redox centers (N2, N4, and N6), oxidation occurred by taking N2 as a unit. Absorption spectra of linear oligoarylamines at various oxidative states were obtained to investigate their charge transfer behaviors. Moreover, DFT-computed isotropic hyperfine coupling constants and spin density were in accordance with the EPR experiment, and gave a close examination of oligoarylamines at charged states.

Dual-channel-mediated spin coupling for one-electron-oxidized cobalt(II)-saddled porphyrin.

Saddle-shaped Co(II)[OET(p-R)PP] (R = CF3, H, CH3) can be readily oxidized with Cl2, Br2, and I2 to the corresponding one-electron-oxidation product Co[OET(p-R)PP]X (X = Cl, Br, I) with the clear character of a ring cation radical. With the series of (1)H and (13)C NMR spectra of these related complexes, both the axial ligand and peripheral substituent of the ring macrocycle are proven to act as a dual channel to tune spin coupling between low-spin Co(II) and a porphyrin π-cation radical. Density functional theory calculations have shown that the antiferromagnetic coupling between spins residing in d(z)(2) and a(2u) are expected to exist as the ground state. The paramagnetic properties are attributed to an a(1u)-type ferromagnetic excited triplet state.