Ping-Wei Chen

2,6-Conjugated anthracene sensitizers for high-performance dye-sensitized solar cells

Metal-free dyes (Ant1 to Ant4) containing a 2,6-conjugated anthracene unit in the spacer have been synthesized. The conversion efficiency (7.52%) of the dye-sensitized solar cell using Ant3 as the sensitizer reached ∼90% of the standard N719-based cell (8.41%). The co-sensitized DSSC using Ant3 and a near-IR dye (SQ2) exhibited an improved efficiency of 8.08%. With addition of a co-adsorbent, CDCA, the cell efficiency (9.11%) of the Ant3-based DSSC surpassed that of the N719-based standard cell. An even higher efficiency of 10.42% was achieved under weak light irradiation.

Y-shaped metal-free D–π–(A)2 sensitizers for high-performance dye-sensitized solar cells

A series of 2,3,5-substituted thiophene-based metal-free dyes with two anchoring groups, D–π–(A)2 (DA), were synthesized for application in DSSCs. Different arylamines and 2-cyanoacrylic acid were used as the electron donor and the electron acceptor, respectively. The DSSC based on DA5 has the best power conversion efficiency (7.28%) among all devices, which is 2 times higher than that of S1 with only one anchoring group. With addition of a co-adsorbent, CDCA, the device performance of all the DA-based DSSCs are improved by 1.03 to 2-fold, with the best efficiency (7.87%) reaching 95% of that of the N719-based standard cell (8.28%). Compared with the S1 congener with only one anchor, the DA dyes can more effectively suppress charge recombination and increase electron injection efficiency, leading to higher open-circuit voltage and short-circuit current.

Dye-sensitized solar cells with low-cost catalytic films of polymer-loaded carbon black on their counter electrode

Dye-sensitized solar cells (DSSCs), consisting of counter electrodes (CEs) with composite films made of carbon black (CB) and conducting polymers such as polypyrrole (PPy) and polyaniline (PANI), were fabricated. A slurry was first prepared with 99 wt% of conducting polymer-loaded CB using the requisite 1 wt% of poly(oxyethylene)-segmented imide (POEM) as the dispersant in ethanol. The conducting polymer-loaded CB was a commercial product with a composition of about 80 wt% of CB and 20 wt% of conducting polymer. The POEM dispersant was required to generate a homogeneous dispersion of the carbon material in the ethanolic solution. The dispersive ability of POEM for CB was demonstrated both visually and through UV–vis absorption spectra and the dynamic light scattering method (DLS). The slurries with PPy/CB and PANI/CB were coated on FTO glasses to prepare CEs for DSSCs. The DSSCs with CEs containing PPy/CB and PANI/CB have shown power conversion efficiencies (η) of 5.85 ± 0.23% and 6.77 ± 0.13%, respectively, while the cells with CEs containing bare CB and bare platinum have shown ηs of 5.35% and 7.24 ± 0.11%, respectively. The dispersive function of POEM for CB to impart high electrocatalytic abilities on the corresponding CEs was responsible for the better performance of the cells for both PPy/CB and PANI/CB than that of the cell with bare CB. Hydrogen-1 nuclear magnetic resonance (1H-NMR), gel permeation chromatography (GPC), scanning electronic microscopy (SEM), cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), incident photo-to-current conversion efficiency (IPCE) spectra, Tafel polarization plots, and rotating disk electrode measurements (RDE) were used to substantiate the explanations.

Phenothiazinedioxide‐Conjugated Sensitizers and a Dual‐TEMPO/Iodide Redox Mediator for Dye‐Sensitized Solar Cells

Metal-free dyes containing a phenothiazinedioxide entity in the spacer were synthesized. The best conversion efficiency (7.47%) of the dye-sensitized solar cell (DSSC) by using new sensitizers with chenodeoxycholic acid as a co-adsorbent and the I(-) /I3 (-) electrolyte reached over 90% of that of the standard N719-based cell (8.10%). A new type of ionic liquid containing the nitroxide radical (N-O(.) ) and iodide was successfully synthesized and applied to the DSSCs. If the I(-) /I3 (-) electrolyte was replaced with a dual redox electrolyte, that is, a TEMPO (2,2,6,6-tetramethylpiperidin-1-oxyl) derivative with a dangling imidazolium iodide entity, the cell exhibited a high open-circuit voltage of 0.85 V and a cell efficiency of 8.36%.

Composite Films Based on Poly(3,4-ethylene dioxythiophene):Poly(styrene sulfonate) Conducting Polymer and TiC Nanoparticles as the Counter Electrodes for Flexible Dye-Sensitized Solar Cells

A composite film of poly(3,4-ethylene dioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) and titanium carbide nanoparticles (TiC-NPs) was deposited on an indium doped tin oxide–poly(ethylene naphthalate) (ITO–PEN) conducting plastic substrate by a doctor blade technique. This ITO–PEN substrate with the composite film was used as the flexible counter electrode (CE) for a plastic dye-sensitized solar cell (DSSC). Performances of the plastic DSSC with the platinum-free CEs containing PEDOT:PSS/TiC-NPs composite was investigated. A solar-to-electricity conversion efficiency (η) of 6.50% was achieved for the pertinent DSSC with PEDOT:PSS/TiC-NPs composite, using commercial N719 dye, which exhibited comparable performance to that of a cell with a sputtered-Pt film on its CE (6.84%). The homogeneous nature of the composite film PEDOT:PSS/TiC-NPs, the uniform distribution of TiC-NPs in its PEDOT:PSS matrix, and the large electrochemical surface area of the composite film are seen to be the factors for the best performance of the pertinent DSSC. Transmission electron microscopy (TEM) and X-ray diffraction (XRD) were used to characterize the TiC-NPs. Scanning electron microscopy (SEM), atomic force microscopy (AFM), and energy dispersive X-ray spectroscopy (EDX) were used to characterize the films. The high efficiency of the cell with PEDOT:PSS/TiC-NPs is explained by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and incident photon-to-current conversion efficiency (IPCE) curves.

Multi-Step-Ahead Reservoir Inflow Forecasting by Artificial Intelligence Techniques

Taiwan is located in themonsoon zone of the North Pacific Ocean and experiences an average of 4-5 typhoons annually. The particular topography of Taiwan makes rivers short and steep, and thus rivers flow rapidly from catchments to reservoirs within a few hours during typhoon events. This study aims to construct realtime multi-step-ahead reservoir inflow forecast models by using Artificial Neural Networks (ANNs) based on radar rainfall data and reservoir inflow data. The Back PropagationNeural Network (BPNN) and the Recurrent Neural Network (RNN) are adopted for forecasting. Results indicate that the correlation coefficients in the testing phases of both models exceed 0.86 for one- to three-hour-ahead forecasts and exceed 0.69 for six-hour-head forecasts. The RNN model outperforms the BPNN model, which indicates the recurrent property of the RNN can effectively improve forecast accuracy when making several step-ahead forecasts. Results demonstrates that the constructed multi-step-ahead rainfall-runoff models can provide valuable instantaneous inflow forecasts for the coming six hours so that decision makers can implement more suitable reservoir operations in consideration of inflow forecasts, rather than just depend on historical scenarios.