High-efficiency, stable bifacial dye-sensitized solar cells (DSSCs) are prepared for application under indoor light conditions. A 3-methoxypropionitrile solvent and cobalt redox couples are utilized to prepare the electrolytes. To obtain the best cell performance, the components of the DSSCs, including electrolytes, photoanodes, and counter electrodes (CEs), are regulated. The experimental results indicate that an electrolyte comprising a Co (II/III) ratio of 0.11/0.025 M, 1.2 M 4-tert-butylpyridine, Y123 dye, a CE with the platinum (Pt) layer thickness of 0.16 nm, and a photoanode with titanium dioxide (TiO2) layer thickness of 10 μm (6 μm main layer and 4 μm scattering layer) are the best conditions under which to achieve a high power conversion efficiency. It is also found that the best cells have high recombination resistance at the photoelectrode/electrolyte interface and low charge transfer resistance at the counter electrode/electrolyte interface, which contributes to, respectively, the high current density and open-circuit voltage of the corresponding cells. This DSSC can achieve efficiencies of 22.66%, 23.48%, and 24.52%, respectively, under T5 light illumination of 201.8, 607.8, and 999.6 lx. For fabrication of bifacial DSSCs with a semitransparent property, photoanodes without the TiO2 scattering layer, as well as an ultrathin Pt film, are utilized. The thicknesses of the TiO2 main layer and Pt film are reregulated. This shows that a Pt film with 0.55 nm thickness has both high transmittance (76.01%) and catalytic activity. By using an 8 μm TiO2 main layer, optimal cell efficiencies of 20.65% and 17.31% can be achieved, respectively, for the front-side and back-side illuminations of 200 lx T5 light. The cells are highly stable during a long-term performance test at both 35 and 50 °C.

No abstract

No abstract

Highly efficient quasi-solid-state dye-sensitized solar cells (QS-DSSCs) are fabricated using nanocomposite gel electrolytes and applied under room light conditions (200 lx). To obtain high energy conversion efficiency in QS-DSSCs, the important components of the DSSC are systematically optimized based on their performance in liquid-state DSSCs. It shows that the liquid cell using the 3-methoxypropionitrile-based cobalt electrolyte has higher efficiency (18.91%) than the cell using the acetonitrile-based electrolyte (17.82%) under 200 lx illumination due to the higher charge recombination resistance at the photoelectrode/electrolyte interface for the 3-methoxypropionitrile system. Poly­(vinylidene fluoride-co-hexafluoropropylene) is utilized as the gelator of the liquid electrolytes to prepare polymer gel electrolytes. Furthermore, to improve the performance of the QS-DSSCs, different metal oxide nanoparticles are introduced as nanofillers of the polymer gel electrolytes. It shows that the zinc oxide nanofillers have a superior performance in increasing the cell efficiency and the energy conversion efficiencies of the QS-DSSCs are higher than those of the corresponding liquid cells. By regulating the concentration of the zinc oxide nanofillers, the efficiency of the 3-methoxypropionitrile based QS-DSSC can achieve a value of 20.11% under 200 lx illumination. This QS-DSSC has a long-term stability at 35 °C.

No abstract

The development of high-performance counter electrodes (CEs) for bifacial dye-sensitized solar cells (DSSCs) using nonplatinum (Pt) material is important to prepare low-cost and high-power conversion efficiency (PCE) DSSCs. In this work, poly(3,4-ethylenedioxythiophene) (PEDOT) CEs were prepared by the electrochemical deposition of PEDOT onto fluorine-doped tin oxide substrates for indoor light application. To obtain a high catalytic and high transparent CE, the thickness of the PEDOT film was controlled. Using Y123 dye and cobalt redox system, the cell performance under different light intensities (200−1000 lx) was studied. The results show that the optimal thickness of PEDOT was 90 nm, which can produce higher diffusivity, higher ionic conductivity, and lower charge transfer resistance at the CE/electrolyte interface. Accordingly, PCEs of 23.98% (200 lx), 25.83% (600 lx), and 26.93% (1000 lx) were achieved for a traditional DSSC photoelectrode containing main layer (ML) and scattering layer (SL). For bifacial cells using a newly developed sandwich photoelectrode with the ML/SL/ML structure, the front-side and rear-side efficiencies under 200 lx illumination were 24.16 and 22.45%, respectively, and the rear-to-front-side efficiency ratio was 93%. These efficiencies were much higher than those obtained using Pt CE.

No abstract

No abstract