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Relevant academic research and scientific papers

Confining perovskite quantum dots in the pores of a covalent-organic framework: quantum confinement- And passivation-enhanced light-harvesting and photocatalysis

All-inorganic lead halide perovskites have attracted significant attention in artificial light-harvesting systems (ALHSs) due to their superior emission tunability and high light-absorption coefficients. However, their relatively low photoluminescence quantum yield (PLQY), surface defects, and poor thermal and air stability severely hinder their actual applications. Here, we demonstrate a simple and versatile method to grow monodisperse CsPbX3(X = Cl, Br, I) perovskite quantum dots (QDs) into the ordered mesopores of a thiol-functionalized covalent-organic framework (COF-SH) as emission-tunable antennas. Intriguingly, benefiting from the quantum confinement and defect-passivation, the resulting CsPbX3@COF-SH not only presents dramatically improved environmental and thermal stability, but also exhibits enhanced PLQY (30.2%), significantly higher than that of pristine CsPbX3perovskite bulk crystals (less than 1.0%). Importantly, the emission spectra of antennas could be precisely tuned by tailoring the halogen component to achieve the well-matched intersections between the emission peak of the antennas and the absorption peak of eosin Y (ESY) or rose bengal (RB) acceptor in ALHSs. As a result, the efficiency of energy transfer achieved from CsPbBr3@COF-SH to ESY and from CsPbBr2I@COF-SH to RB reached up to 94.4% and 93.6%, respectively. To better imitate natural photosynthesis, ESY-CsPbBr3@COF-SH and RB-CsPbBr2I@COF-SH systems were employed as photochemical catalysts for C-H selenation and cross-coupling/annulation reactions, respectively, and both systems showed elevated catalytic activity with excellent yields of up to 99.3% and 95.5% and far surpassing that of ESY or RB alone. This work clearly demonstrates the great advantages of COFs in the fabrication of embedded perovskite QDs with enhanced photoluminescence, thereby facilitating light-harvesting and promoting light-converting applications.

Wide bandgap copolymers with vertical benzodithiophene dicarboxylate for high-performance polymer solar cells with an efficiency up to 7.49%

In aiming to build novel wide band-gap high-performance photovoltaic donor materials, a vertical benzo[1,2-b:4,5-b′]dithiophene-2,6-dicarboxylate (V-BDTC) with a weak electron-withdrawing character was primarily developed. And its wide band-gap (WBG) copolymers PV-BDTC1 and PV-BDTC2 were designed and synthesized, which contain a traditional electron-donating unit of 4,8-disubstituted benzo[1,2-b:4,5-b′] dithiophene (BDT) derivative with diethylhexyloxy for the former and diethylhexylthiophenyl for the latter. It is found that the weak electron-withdrawing V-BDTC unit endows its copolymers with a WBG up to 2.09 eV and a deep HOMO energy level of ～5.67 eV. Furthermore, PV-BDTC2 exhibits much better photovoltaic properties than PV-BDTC1 in the solution-processing polymer solar cells (PSCs) with a higher open-circuit voltage (Voc) of 1.03 V and an increased power conversion efficiency (PCE) of 7.49%. To the best of our knowledge, this PCE value is the highest level recorded for copolymers with a WBG over 2.0 eV in the PSCs to date, along with a remarkable Voc over 1.0 V. This work provides a feasible strategy to develop a novel promising electron-withdrawing building block and its high-performance WBG copolymers based on the BDT unit.

Synthesis, characterization, and fluorescence quenching of novel cationic phenyl-substituted poly(p-phenylenevinylene)s

Three new phenyl-substituted poly(p-phenylenevinylene) (Ph-PPV) derivatives with amino-functionalized groups were synthesized through either Gilch reaction for poly{2,5-bis[4′-2-(N,N-diethylamino)ethoxyphenyl]-1,4-phenylenevinylene (P1) or Wittig reaction for poly{2,5-bis(4′-decyloxyphenyl)-1,4-phenylenevinylene-alt-2,5-bis[4′ -2-(N,N-diethylamino)ethoxyphenyl]-1,4-phenylenevinylene} (P2) and poly(2,5-bis{4′-2-[2-(2-methoxyethoxy)ethoxy]ethoxyphenyl}-1,4-phenylenevi nylene-alt-2,5-bis[4′-2-(N,N-diethylamino)ethoxyphenyl]-1,4- phenylenevinylene) (P3). Green light-emitting cationic polymers, poly{2,5-bis(4′-decyloxyphenyl)-1,4-phenylenevinylene-alt-2,5-bis[4′ -2-(N,N,N-triethylammonium)ethoxyphenyl]-1,4-phenylenevinylene} dibromide (P2′) and poly(2,5-bis{4′-2-[2-(2-methoxyethoxy)ethoxy]ethoxyphenyl}-1,4-phenylenevi nylene-alt-2,5-bis[4′-2-(N,N,N-triethylammonium)ethoxyphenyl]-1, 4-phenylenevinylene) dibromide (P3′), were prepared from the neutral polymers P2 and P3, respectively. Water solubility was achieved on P3′ through increase of the hydrophilicity of the side chains. The acid-assistant reversible solubility of P1 makes it promising in preparing light-emitting multilayer devices. On the basis of FT-IR and 1H NMR spectra, it was found that P1 is primarily of trans-vinyl while P2 and P3 are of 80% and 81% cis-vinyl, respectively, which depends on the polymerization method employed. The bulky phenyl substituents successfully impeded the interchain interaction which led to quantum efficiency as films comparable to that of solutions. Quaternization also resulted in more twisted conformation of the polymer main chain which was supported by both blue-shifted absorption and reduced quantum efficiency of P2′ and P3′ in solutions and as films than that of the neutral polymers. The fluorescence of P3′ was efficiently quenched by an anionic quencher Fe(CN)64-, Ksv of which is 3.3 × 106 M-1. However, a modified Stern-Volmer plot showed that 9% of the fluophores could not be accessible to the quencher, which may result from the twisted conformation or intermolecular aggregation.