Suppressing Interfacial Charge Recombination in Electron-Transport-Layer-Free Perovskite Solar Cells to Give an Efficiency Exceeding 21 %

The performances of electron-transport-layer (ETL)-free perovskite solar cells (PSCs) are still inferior to ETL-containing devices. This is mainly due to severe interfacial charge recombination occurring at the transparent conducting oxide (TCO)/perovskite interface, where the photo-injected electrons in the TCO can travel back to recombine with holes in the perovskite layer. Herein, we demonstrate for the first time that a non-annealed, insulating, amorphous metal oxyhydroxide, atomic-scale thin interlayer (ca. 3 nm) between the TCO and perovskite facilitates electron tunneling and suppresses the interfacial charge recombination. This largely reduced the interfacial charge recombination loss and achieved a record efficiency of 21.1 % for n-i-p structured ETL-free PSCs, outperforming their ETL-containing metal oxide counterparts (18.7 %), as well as narrowing the efficiency gap with high-efficiency PSCs employing highly crystalline TiO₂ ETLs.     

Molecular Level Modulation of Anthraquinone-containing Resorcinol-formaldehyde Resin Photocatalysts for H2O2 Production with Exceeding 1.2 % Efficiency

Designing polymeric photocatalysts at the molecular level to modulate the photogenerated charge behavior is a promising and challenging strategy for efficient hydrogen peroxide (H₂O₂) photosynthesis. Here, we introduce electron-deficient 1,4-dihydroxyanthraquinone (DHAQ) into the framework of resorcinol-formaldehyde (RF) resin, which modulates the donor/acceptor ratio from the perspective of molecular design for promoting the charge separation. Interestingly, H₂O₂ can be produced via oxygen reduction and water oxidation pathways, verified by isotopic labeling and in situ characterization techniques. Density functional theory (DFT) calculations elucidate that DHAQ can reduce the energy barrier for H₂O₂ production. RF-DHAQ exhibits excellent overall photosynthesis of H₂O₂ with a solar-to-chemical conversion (SCC) efficiency exceeding 1.2 %. This work opens a new avenue to design polymeric photocatalysts at the molecular level for high-efficiency artificial photosynthesis.     

Efficient and Saturated Red Light-Emitting Electrochemical Cells Based on Cationic Iridium(III) Complexes with EQE up to 9.4 %

Solid-state light-emitting electrochemical cells (LECs) have several advantages, such as low-voltage operation, compatibility with inert metal electrodes, large-area flexible substrates, and simple solution-processable device architectures. However, most of the studies on saturated red LECs show low or moderate device efficiencies (external quantum efficiency (EQE) <3.3 %). In this work, we demonstrate a series of five red-emitting cationic iridium complexes ( RED1- - RED5 ) with 2,2′-biquinoline ligands and test their electroluminescence (EL) characteristics in LECs. The Commission Internationale de l′Eclairage (CIE) 1931 coordinates for the LECs based on these complexes are all beyond the National Television System Committee (NTSC) red standard point (0.67, 0.33). The maximal EQE of the neat-film RED1 -based LECs reaches 7.4 %. The reddest complex, RED3 , is doped in the blue-emitting host complex, BG , to fabricate host–guest LECs. The maximal EQE of the host–guest LECs (1 wt % complex RED3 ) reaches 9.4 %, which is among the highest reported for the saturated red LECs.     

Miscibility-Controlled Phase Separation in Double-Cable Conjugated Polymers for Single-Component Organic Solar Cells with Efficiencies over 8 %

A record power conversion efficiency of 8.40 % was obtained in single-component organic solar cells (SCOSCs) based on double-cable conjugated polymers. This is realized based on exciton separation playing the same role as charge transport in SCOSCs. Two double-cable conjugated polymers were designed with almost identical conjugated backbones and electron-withdrawing side units, but extra Cl atoms had different positions on the conjugated backbones. When Cl atoms were positioned at the main chains, the polymer formed the twist backbones, enabling better miscibility with the naphthalene diimide side units. This improves the interface contact between conjugated backbones and side units, resulting in efficient conversion of excitons into free charges. These findings reveal the importance of charge generation process in SCOSCs and suggest a strategy to improve this process: controlling miscibility between conjugated backbones and aromatic side units in double-cable conjugated polymers.     

Site Engineering of Covalent Organic Frameworks for Regulating Peroxymonosulfate Activation to Generate Singlet Oxygen with 100 % Selectivity

Singlet oxygen (¹O₂) is an excellent reactive oxygen species (ROSs) for the selective conversion of organic matter, especially in advanced oxidation processes (AOPs). However, due to the huge dilemma in synthesizing single-site type catalysts, the control and regulation of ¹O₂ generation in AOPs is still challenging and the underlying mechanism remains largely obscure. Here, taking advantage of the well-defined and flexibly tunable sites of covalent organic frameworks (COFs), we report the first achievement in precisely regulating ROSs generation in peroxymonosulfate (PMS)-based AOPs by site engineering of COFs. Remarkably, COFs with bipyridine units (BPY-COFs) facilitate PMS activation via a nonradical pathway with 100 % ¹O₂, whereas biphenyl-based COFs (BPD-COFs) with almost identical structures activate PMS to produce radicals (⋅OH and SO₄^.−). The BPY-COFs/PMS system delivers boosted performance for selective degradation of target pollutants from water, which is ca. 9.4 times that of its BPD-COFs counterpart, surpassing most reported PMS-based AOPs systems. Mechanism analysis indicated that highly electronegative pyridine-N atoms on BPY-COFs provide extra sites to adsorb the terminal H atoms of PMS, resulting in simultaneous adsorption of O and H atoms of PMS on one pyridine ring, which facilitates the cleavage of its S−O bond to generate ¹O₂.     

Unidirectional Sidechain Engineering to Construct Dual-Asymmetric Acceptors for 19.23 % Efficiency Organic Solar Cells with Low Energy Loss and Efficient Charge Transfer

Achieving both high open-circuit voltage (V_oc) and short-circuit current density (J_sc) to boost power-conversion efficiency (PCE) is a major challenge for organic solar cells (OSCs), wherein high energy loss (E_loss) and inefficient charge transfer usually take place. Here, three new Y-series acceptors of mono-asymmetric asy-YC11 and dual-asymmetric bi-asy-YC9 and bi-asy-YC12 are developed. They share the same asymmetric D₁AD₂ (D₁=thieno[3,2-b]thiophene and D₂=selenopheno[3,2-b]thiophene) fused-core but have different unidirectional sidechain on D₁ side, allowing fine-tuned molecular properties, such as intermolecular interaction, packing pattern, and crystallinity. Among the binary blends, the PM6 : bi-asy-YC12 one has better morphology with appropriate phase separation and higher order packing than the PM6 : asy-YC9 and PM6 : bi-asy-YC11 ones. Therefore, the PM6 : bi-asy-YC12-based OSCs offer a higher PCE of 17.16 % with both high V_oc and J_sc, due to the reduced E_loss and efficient charge transfer properties. Inspired by the high V_oc and strong NIR-absorption, bi-asy-YC12 is introduced into efficient binary PM6 : L8-BO to construct ternary OSCs. Thanks to the broadened absorption, optimized morphology, and furtherly minimized E_loss, the PM6 : L8-BO : bi-asy-YC12-based OSCs achieve a champion PCE of 19.23 %, which is one of the highest efficiencies among these annealing-free devices. Our developed unidirectional sidechain engineering for constructing bi-asymmetric Y-series acceptors provides an approach to boost PCE of OSCs.     

Hard-Sphere Random Close-Packed Au47Cd2(TBBT)31 Nanoclusters with a Faradaic Efficiency of Up to 96 % for Electrocatalytic CO2 Reduction to CO

Metal nanoclusters have recently attracted considerable attention, not only because of their special size range but also because of their well-defined compositions and structures. However, subtly tailoring the compositions and structures of metal nanoclusters for potential applications remains challenging. Now, a two-phase anti-galvanic reduction (AGR) method is presented for precisely tailoring Au₄₄(TBBT)₂₈ to produce Au₄₇Cd₂(TBBT)₃₁ nanoclusters with a hard-sphere random close-packed structure, exhibiting Faradaic efficiencies of up to 96 % at −0.57 V for the electrocatalytic reduction of CO₂ to CO.     

Hydroquinone Decorated with Alkyne,Quaternary Ammonium,and Hydrophobic Motifs to Mitigate Corrosion of X-60 Mild Steel in 15 wt.% HCl

1-(6-Bromohexyloxy)-4-propargyloxybenzene upon quaternization with 3-dimethylamino-1-propanol and N,N-dimethyldodecylamine produced two new inhibitor molecules: N-[6-(4-Propargyloxyphenoxy)hexyl]-N,N-dimethyl-N-(3-hydroxypropyl)ammonium bromide (PHAB) and N-[6-(4-Propargyloxyphenoxy)hexyl]-N,N-dimethyl-N-dodecylammonium bromide (PDAB), respectively, in excellent yields. The inhibitor molecules were characterized by elemental analysis, Fourier transform infrared spectroscopy, ¹H NMR, and ¹³C NMR spectroscopy. The inhibitors were evaluated for X-60 mild steel corrosion in 15 wt.% HCl using different electrochemical and gravimetric techniques. The potentiodynamic polarization confirms both the inhibitors as mixed-type corrosion inhibitors. A low concentration (15 ppm) of PDAB has demonstrated excellent corrosion inhibition efficiencies of 97%, 98%, and 86% at 25 °C, 50 °C, and 70 °C, respectively, for 24 h exposure time. SEM and EDX spectra reveal that the adsorptions of corrosion inhibitors on X-60 mild steel create a protective film that serves as a barrier to mitigate the corrosion process. The X-ray photoelectron spectroscopy confirmed the chemical interaction between the corrosion inhibitors and mild steel, which was predicted by the Langmuir adsorption model. Assembly of inhibitive motifs of the alkyne, π-electron-rich aromatic, quaternary ammonium and C₁₂ alkyl chain hydrophobe in PDAB has augmented its inhibiting action.