Cheng-Si Tsao

Covalent organic frameworks (COFs) constitute a class of functional porous materials with high stability and tunable porosity, rendering them attractive for adsorption-based applications. To study the interaction between COFs and target molecules, the quartz crystal microbalance with dissipation monitoring (QCM-D), which offers high sensitivity to mass changes with a sampling rate of ∼50 ms, is a well-suited tool for analyzing adsorption processes in real time. However, current QCM-D-based adsorption studies have remained largely qualitative, primarily relying on comparison of the magnitudes of frequency shifts. This occurs because the intrinsic mass of the film coated onto QCM-D sensors is often not determined, which prevents the quantification of the adsorption capacity. To address this challenge, a flow-based strategy to directly grow homogeneous COF thin films on sensor surfaces under QCM-D monitoring was established. This approach facilitates reliable mass determination, robust film attachment, and reproducible film preparation with precise control over film growth. To account for the contribution of the embedded solvent during film deposition, deuterated solvent exchange was performed. Through the use of methylene blue as a model adsorbate, liquid-phase QCM-D measurements revealed adsorption capacities of ∼31 mg·g^–1 for triformylphloroglucinol-phenylenediamine (TpPa) COF and ∼259 mg·g^–1 for TpPa-SO₃H within 60 min. It was found that a single kinetic model cannot describe the entire process. Instead, the pseudo-second-order (PSO) model best described the initial surface-controlled phase, whereas subsequent uptake was dominated by intraparticle diffusion (IPD). A hybrid kinetic model with a time-weighted function successfully captured the transition between these two stages and provided insights into the difference in mass transportation in TpPa and TpPa-SO₃H. This methodology provides a platform for high-speed, quantitative and real-time liquid-phase analysis of COF–guest interactions with high potential for extension to other porous materials.

Developing sustainable, high-performance elastomers for tire applications has become a growing priority for the chemical industry, driven by environmental mandates and the functional demands of modern transportation. In response, additive engineering is increasingly employed to replace conventional silane coupling agents (SCAs), which raise environmental concerns and constrain optimization of the rolling resistance (RR)–wet grip (WG) trade-off. A central challenge in this domain lies in elucidating how interfacial modifiers reconfigure filler architecture and influence macroscopic properties. In this study, we introduce a novel small angle X-ray scattering (SAXS)-guided analytical framework that integrates a mass-fractal model with a gel-like network model to resolve the hierarchical three-tiered structure of poly(ethylene glycol) (PEG)-modified, silica-filled tire compounds. This hybrid model enables the quantitative extraction of cluster radius and—critically—the contribution of occluded rubber domains, a morphological feature often suggested visually but seldom structurally characterized. In contrast to a widely used SCA, which enhances filler dispersion via covalent silica–rubber linkages, PEG induces greater filler aggregation and occluded rubber formation through hydrogen bonding, while simultaneously promoting interfacial slippage under dynamic strain. These coexisting mesoscale features—quantified via SAXS and directly linked to dynamic mechanical properties—result in a 40% reduction in RR, a 14% enhancement in WG, and 81% higher stiffness relative to the SCA-modified system. This mechanistic breakthrough diverges from conventional dispersion-centric frameworks and establishes PEG as a viable SCA-free alternative. More broadly, this work demonstrates a transferable, structure-informed strategy for the design of next-generation high-performance, environmentally friendly rubber nanocomposites.

In recent years, third-generation solar cells have experienced a remarkable growth in efficiency, making them a highly promising alternative energy solution. Currently, high-efficiency solar cells often use top electrodes fabricated by thermal evaporation, which rely on high-cost and high energy-consumption vacuum equipment, raising significant concerns for mass production. This study develops a method for fabricating silver electrodes using the screen-printing process, aiming to achieve solar cell production through an all-solution coating process. By selecting appropriate blocking-layer materials and optimizing the process, we have achieved device efficiencies for organic photovoltaics (OPVs) with screen-printed silver electrodes comparable to those with silver electrodes fabricated by thermal evaporation. Furthermore, we developed a method to cure the silver ink using near-infrared (NIR) annealing, significantly reducing the curing time from 30 min with hot air annealing to just 5 s. Additionally, by employing sheet-to-sheet (S2S) slot-die coating, we scaled up the device area and completed module development, successfully verifying stability in ambient air. We have also extended the application of screen-printed silver electrodes to perovskite solar cells (PSCs).

In pursuing high stability and power conversion efficiency for organic photovoltaics (OPVs), a sequential deposition (SD) approach to fabricate active layers with p-i-n structures (where p, i, and n represent the electron donor, mixed donor:acceptor, and electron acceptor regions, respectively, distinctively different from the bulk heterojunction (BHJ) structure) has emerged. Here, we present a novel approach that by incorporating two polymer donors, PBDBT-DTBT and PTQ-2F, and one small-molecule acceptor, BTP-3-EH-4Cl, into the active layer with sequential deposition, we formed a device with nanometer-scale twin p-i-n structured active layer. The twin p-i-n PBDBT-DTBT:PTQ-2F/BTP-3-EH-4Cl device involved first depositing a PBDBT-DTBT:PTQ-2F blend under layer and then a BTP-3-EH-4Cl top layer and exhibited an improved power conversion efficiency (PCE) value of 18.6%, as compared to the 16.4% for the control BHJ PBDBT-DTBT:PTQ-2F:BTP-3-EH-4Cl device or 16.6% for the single p-i-n PBDBT-DTBT/BTP-3-EH-4Cl device. The PCE enhancement resulted mainly from the twin p-i-n active layer's multiple nanoscale charge carrier pathways that contributed to an improved fill factor and faster photocurrent generation based on transient absorption studies. The PBDBT-DTBT:PTQ-2F/BTP-3-EH-4Cl film possessed a vertical twin p-i-n morphology that was revealed through secondary ion mass spectrometry and synchrotron grazing-incidence small-angle X-ray scattering analyses. The thermal stability (T₈₀) at 85 °C of the twin p-i-n PBDBT-DTBT:PTQ-2F/BTP-3-EH-4Cl device surpassed that of the single p-i-n PBDBT-DTBT/BTP-3-EH-4Cl devices (906 vs 196 h). This approach of providing a twin p-i-n structure in the active layer can lead to substantial enhancements in both the PCE and stability of organic photovoltaics, laying a solid foundation for future commercialization of the organic photovoltaics technology.

This study focuses on the hole transport layer of molybdenum trioxide (MoO₃) for inverted bulk heterojunction (BHJ) organic photovoltaics (OPVs), which were fabricated using a combination of a spray coating and low-temperature annealing process as an alternative to the thermal evaporation process. To achieve a good coating quality of the sprayed film, the solvent used for solution-processed MoO₃ (S-MoO₃) should be well prepared. Isopropanol (IPA) is added to the as-prepared S-MoO₃ solution to control its concentration. MoO₃ solutions at concentrations of 5 mg/mL and 1 mg/mL were used for the spray coating process. The power conversion efficiency (PCE) depends on the concentration of the MoO₃ solution and the spray coating process parameters of the MoO₃ film, such as flow flux, spray cycles, and film thickness. The results of devices fabricated from solution-processed MoO₃ with various spray fluxes show a lower PCE than that based on thermally evaporated MoO₃ (T-MoO₃) due to a limiting FF, which gradually increases with decreasing spray cycles. The highest PCE of 2.8% can be achieved with a 1 mg/mL concentration of MoO₃ solution at the sprayed flux of 0.2 mL/min sprayed for one cycle. Additionally, S-MoO₃ demonstrates excellent stability. Even without any encapsulation, OPVs can retain 90% of their initial PCE after 1300 h in a nitrogen-filled glove box and under ambient air conditions. The stability of OPVs without any encapsulation still has 90% of its initial PCE after 1300 h in a nitrogen-filled glove box and under air conditions. The results represent an evaluation of the feasibility of solution-processed HTL, which could be employed for a large-area mass production method.

The ability of organic photovoltaics (OPVs) to be deposited on flexible substrates by roll-to-roll (R2R) processes is highly attractive for rapid mass production. Many research teams have demonstrated the great potential of flexible OPVs. However, the fabrication of R2R-coated OPVs is quite limited. There is still a performance gap between the R2R flexible OPVs and the rigid OPVs. In this study, we demonstrate the promising photovoltaic characteristics of flexible OPVs fabricated from blends of low bandgap polymer poly[(2,6-(4,8-bis(5-(2-ethylhexyl)thiophen-2-yl)-benzo[1,2-b:4,5-b′]dithiophene))-alt-(5,5-(1′,3′-di-2-thienyl-5′,7′-bis(2-ethylhexyl)benzo[1′,2′-c:4′,5′-c′]dithiophene-4,8-dione)] (PBDB-T) and non-fullerene 3,9-bis(2-methylene-(3-(1,1-dicyanomethylene)-indanone))-5,5,11,11-tetrakis(4-hexylphenyl)-dithieno[2,3-d:2′,3′-d′]-s-indaceno[1,2-b:5,6-b′]dithiophene (ITIC). We successfully R2R slot-die coated the flexible OPVs with high power conversion efficiency (PCE) of over 8.9% under irradiation of simulated sunlight. Our results indicate that the processing parameters significantly affect the PCE of R2R flexible OPVs. By adjusting the amount of solvent additive and processing temperature, as well as optimizing thermal annealing conditions, the high PCE of R2R slot-die coated OPVs can be obtained. These results provide significant insights into the fundamentals of highly efficient OPVs for the R2R slot-die coating process.

Wood cellulose microfibril (CMF) is the most abundant organic substance on Earth but its nanostructure remains poorly understood. There are controversies regarding the glucan chain number (N) of CMFs during initial synthesis and whether they become fused afterward. Here, we combined small-angle X-ray scattering, solid-state nuclear magnetic resonance and X-ray diffraction analyses to resolve CMF nanostructures in native wood. We developed small-angle X-ray scattering measurement methods for the cross-section aspect ratio and area of the crystalline-ordered CMF core, which has a higher scattering length density than the semidisordered shell zone. The 1:1 aspect ratio suggested that CMFs remain mostly segregated, not fused. The area measurement reflected the chain number in the core zone (N_core). To measure the ratio of ordered cellulose over total cellulose (R_oc) by solid-state nuclear magnetic resonance, we developed a method termed global iterative fitting of T_1ρ-edited decay (GIFTED), in addition to the conventional proton spin relaxation editing method. Using the formula N = N_core/R_oc, most wood CMFs were found to contain 24 glucan chains, conserved between gymnosperm and angiosperm trees. The average CMF has a crystalline-ordered core of ~2.2 nm diameter and a semidisordered shell of ~0.5 nm thickness. In naturally and artificially aged wood, we observed only CMF aggregation (contact without crystalline continuity) but not fusion (forming a conjoined crystalline unit). This further argued against the existence of partially fused CMFs in new wood, overturning the recently proposed 18-chain fusion hypothesis. Our findings are important for advancing wood structural knowledge and more efficient use of wood resources in sustainable bio-economies.