98 research outputs found

    Doping ZnO with Water/Alcohol-Soluble Small Molecules as Electron Transport Layers for Inverted Polymer Solar Cells

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    By doping ZnO with porphyrin small molecules (FNEZnP-OE and FNEZnP-T) as cathode electron transport layers (ETLs), the inverted polymer solar cells (i-PSC) with PTB7:PC<sub>71</sub>BM (PTB7: polythieno­[3,4-<i>b</i>]-thiophene-<i>co</i>-benzodithiophene, PC<sub>71</sub>BM:[6, 6]-phenyl-C<sub>71</sub>-butyric acid methyl ester) as the active materials exhibit enhanced device performance. While the power conversion efficiency (PCE) of the PSCs with pure ZnO ETL is 7.52%, that of the devices with FNEZnP-T-doped ZnO ETL shows a slightly improved PCE of 8.09%, and that of the PSCs with FNEZnP-OE-doped ZnO ETL is further enhanced up to 9.24% with an over 20% improvement compared to that with pure ZnO ETL. The better performance is contributed by the better interfacial contact and reduced work function induced by 9,9-bis­(30-(<i>N</i>,<i>N</i>-dimethylamino)­propyl)-2,7-fluorenes and 3,4-bis­(2-(2-methoxy-ethoxy)-ethoxy)-phenyls in the porphyrin small molecules. More importantly, the PCE is still higher than 8% even when the thickness of FNEZnP-OE-doped ZnO ETL is up to 110 nm, which are important criteria for eventually making organic photovoltaic modules with roll-to-roll coat processing

    Revealing the AcOH-Induced Dissolution Mechanism of Alcohol-Soluble Interlayers

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    Water/alcohol-soluble cathode interlayers are widely utilized in organic electronic devices. However, the mechanism by which acetic acid (AcOH) facilitates the solubility of neutral cathode interlayers in water/alcohol remains unclear. This paper focuses on the AcOH-induced dissolution mechanism of neutral cathode interlayer materials and establishes quantitative relationships for chemical reactions. It was found that AcOH could react acid–base with the amino groups of PFN or PDIN, resulting in the formation of trace amounts of quaternary ammonium salts, which ultimately enhance the solubility of PFN and PDIN in methanol. Additionally, this study clarifies the debate about the role of neutral cathode interlayers in organic electronic devices: It is primarily the unprotonated groups of water/alcohol-soluble cathode interlayers that play a critical role in interfacial modification rather than the protonated groups produced by postacid reaction, which lays an important theoretical foundation for the development of high-performance interfacial materials

    Chemisorption-Induced Robust and Homogeneous Tungsten Disulfide Interlayer Enables Stable PEDOT-Free Organic Solar Cells with Over 19% Efficiency

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    Construction of a high-quality charge transport layer (CTL) with intimate contact with the substrate via tailored interface engineering is crucial to increase the overall charge transfer kinetics and stability for a bulk-heterojunction (BHJ) organic solar cell (OSC). Here, we demonstrate a surface chemistry strategy to achieve a homogeneous composite hole transport layer (C-HTL) with robust substrate contact by self-assembling two-dimensional tungsten disulfide (WS2) nanosheets on a thin molybdenum oxide (MoO3) film-evaporated indium tin oxide (ITO) substrate. It is found that over such a well-defined C-HTL, WS2 is homogeneously tethered on the ITO/MoO3 substrate stemming from the strong electronic coupling interaction between the building blocks, which enables a favorable interfacial configuration in terms of uniformity. As a result, the D18:L8-BO-based OSC with C-HTL exhibits a power conversion efficiency (PCE) of 19.23%, an 11% improvement over the WS2-based control device, and the highest efficiency among single-junction PEDOT-free binary BHJ OSCs

    Monitoring the Chemical Production of Citrus-Derived Bioactive 5‑Demethylnobiletin Using Surface-Enhanced Raman Spectroscopy

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    To develop an accurate and convenient method for monitoring the production of citrus-derived bioactive 5-demethylnobiletin from the demethylation reaction of nobiletin, we compared surface-enhanced Raman spectroscopy (SERS) methods with a conventional high-performance liquid chromatography (HPLC) method. Our results show that both the substrate- and solution-based SERS methods correlated with the HPLC method very well. The solution method produced lower root-mean-square error of calibration and higher correlation coefficient than the substrate method. The solution method used an “affinity chromatography”-like procedure to separate the reactant nobiletin from the product 5-demthylnobiletin based on their different binding affinities to the silver dendrites. The substrate method was found simpler and faster to collect the SERS “fingerprint” spectra of the samples because no incubation between samples and silver was needed and only a trace amount of samples was required. Our results demonstrated that the SERS methods were superior to the HPLC method in conveniently and rapidly characterizing and quantifying 5-demethylnobiletin production

    Cesium-Doped Vanadium Oxide as the Hole Extraction Layer for Efficient Perovskite Solar Cells

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    In this study, we report the utilization of low-temperature solution-processed Cs-doped VO<sub>X</sub> thin films as the hole extraction layers (HELs) in perovskite solar cells (PSCs). It is found that the VO<sub>X</sub>:<i>y</i>Cs (where <i>y</i> is the mole ratio of Cs versus V and <i>y</i> = 0.1, 0.3, and 0.5) thin films possess better electrical conductivities than that of the pristine VO<sub>X</sub> thin film. As a result, the PSCs incorporated with the VO<sub>X</sub>:<i>y</i>Cs HEL exhibit large fill factors and high short-circuit currents, with consequently high power conversion efficiencies, which is more than 30% enhancement as compared with pristine VO<sub>X</sub> HEL. Our studies provide a facial way to enhance the electrical conductivity of the hole extraction layer for boosting device performance of perovskite solar cells

    Modifying the Chemical Structure of a Porphyrin Small Molecule with Benzothiophene Groups for the Reproducible Fabrication of High Performance Solar Cells

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    A porphyrin-based molecule DPPEZnP-BzTBO with bulky benzothiophene groups was designed and synthesized as an electron donor material for bulk heterojunction (BHJ) solar cells. The optimized devices under thermal annealing (TA) and then chloroform solvent vapor anneanling (SVA) for 80 s exhibited an outstanding power conversion efficiencie (PCE) of 9.08%. Contrasted with the smaller thienyl substituted analogues we reported previously, DPPEZnP-BzTBO-based BHJ solar cells exhibited a higher open circuit voltage due to the lower highest occupied molecular orbital energy level. The TA post-treatment of the active layers induced the formation of more crystallized components, and the subsequent SVA provided a driving force for the domain growth, resulting in more obvious phase segregation between the donor and the acceptor in nanoscale. Furthermore, the PCEs kept above 95% upon the further SVA treatment within the time range of 60 to 95 s probably because the bulky benzothiophene groups retard the too quick change of crystallinity, providing a wide processing window for the reproducible device fabrication
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