Preparation of Nano-composite Gel Electrolytes with Metal Oxide Additives for Dye-sensitized Solar Cells

Biodiesel production from the Scenedesmus sp. and utilization of pigment from de-oiled biomass as sensitizer in the dye-sensitized solar cell (DSSC) for performance enhancement

Dye-sensitized solar cell (DSSC) using algal photosynthetic pigments has got rampant attention as it converts sunlight into electricity. Therefore, in this present research, the neutral lipid extracted from the green alga Scenedesmus sp. was used for biodiesel production, and concurrently, pigments extracted from the de-oiled biomass cake were used as a sensitizer in DSSC to evaluate its performance efficacy with and without PVDF (Polyvinylidene fluoride). Initially, neutral lipids extracted from the Scenedesmus sp. were converted to biodiesel with a yield of 72.9%, and the de-oiled biomass was subjected to pigment extraction (17.65 mg/g) to use as a sensitizer in DSSC. This study proposes two DSSC test models, i.e., PVDF (Polyvinylidene fluoride) - bound cell and cell without any PVDF binder. For the PVDF-coated DSSC, the average energy conversion efficiency reached about 14.3%, the open circuit voltage was 0.55 V, and the short circuit current was 144.5 mA. The unbound cells showed a reduction in efficiency, voltage, and current, and notably, efficiency of 10.44% on day 1 was decreased to 3.32%, and the open circuit voltage and short circuit current of 0.38V and 144 mA were decreased to 0.24V and 130 mA after 10 days, under 40 mW/cm2 input power. The PVDF-coated solar cell has maintained its efficiency range of 16.32%-11.22%, which is higher than the PVDF-unbound cell for a tested timeline of 30 days. The fill factor of 0.47 was observed in PVDF- unbound DSSC under 40 mW/cm2 as input power, while it was increased to 0.577 when PVDF was used as a binder. The PVDF-coated cell has low degradation compared with the PVDF-uncoated cell. These results offer dual benefits as the production of biodiesel from microalgal lipids and electricity generation from the DSSC using the pigments of biodiesel-extracted algal biomass.

Modification of DSSC Based on Polymer Composite Gel Electrolyte with Copper Oxide Nanochain by Shape Effect

Solvent evaporation and leakage of liquid electrolytes that restrict the practicality of dye-sensitized solar cells (DSSCs) motivate the quest for the development of stable and ionic conductive electrolyte. Gel polymer electrolyte (GPE) fits the criteria, but it still suffers from low efficiency due to insufficient segmental motion within the electrolytes. Therefore, incorporating metal oxide nanofiller is one of the approaches to enhance the performance of electrolytes due to the presence of cross-linking centers that can be coordinated with the polymer segments. In this research, polymer composite gel electrolytes (PCGEs) employing poly (vinyl butyral-co-vinyl alcohol-co-vinyl acetate) (P(VB-co-VA-co-VAc)) terpolymer as host polymer, tetrapropylammonium iodide (TPAI) as dopant salt, and copper oxide (CuO) nanoparticles as the nanofillers were produced. The CuO nanofillers were synthesized by sonochemical method and subsequently calcined at different temperatures (i.e., 200, 350, and 500 °C), denoted as CuO-200, CuO-350, and CuO-500, respectively. All CuO nanoparticles have different shapes and sizes that are connected in a chain which impact the amorphous phase and the roughness of the surface, proven by the structural and the morphological analyses. It was found that the PCGE consisting of CuO-350 exhibited the highest ionic conductivity of 2.54 mS cm⁻¹ and apparent diffusion coefficient of triiodide of 1.537 × 10⁻⁴ cm² s⁻¹. The enhancement in the electrochemical performance of the PCGEs is correlated with the change in shape (rod to sphere) and size of CuO particles which disrupted the structural order of the polymer chain, facilitating the redox couple transportation. Additionally, a DSSC was fabricated and achieved the highest power conversion efficiency of 7.05% with J_SC of 22.1 mA cm⁻², V_OC of 0.61 V, and FF of 52.4%.

Highly efficient and stable ionic liquid-based gel electrolytes

Gel electrolytes are promising candidates for dye-sensitized solar cells (DSSCs) and other devices, but the ways to obtain stable gels always result in sacrifice of their ionic conductivity. This contradiction seriously limits the practical application of gel electrolytes. Herein, a new design strategy using rich carboxylic group-modified silica nanoparticles (COOH-SiO₂) with a branched, well-organized framework to develop ionic liquid-based gel electrolytes possessing high conductivity is demonstrated. The branched network of COOH-SiO₂ and the strong interaction in electrolytes result in the effective solidification of ionic liquids. Moreover, adding COOH-SiO₂ to ionic liquid electrolytes contributes to salt dissociation, decreases the activation energy, and improves the charge transport and recombination characteristics at the electrolyte/electrode interface. DSSCs fabricated with COOH-SiO₂ nanoparticles deliver a higher short-circuit photocurrent density (J_sc) than the reference cell. A maximum efficiency of 8.02% with the highest J_sc value of 16.60 mA cm^-2 is obtained for solar cells containing 6 wt% COOH-SiO₂.

Unveiling the Relationship between the Surface Chemistry of Nanoparticles and Ion Transport Properties of the Resulting Composite Electrolytes

Fundamental understanding of the transport properties within nanoparticle composite electrolytes is necessary for the development of next-generation electrochemical devices. Herein, the effect of surface-modified silica nanoparticles with aminophenyl, amide, and sulfonate functional groups (AP-SiO₂, AM-SiO₂, and SU-SiO₂) on the ion transport properties of composite electrolytes is systematically investigated. The competition between surface repulsive and attractive interactions of nanoparticles is reflected in the nature of the morphology and particle network in electrolytes, further affecting the ionic conductivity of electrolytes and diffusion coefficient of ions. The obvious decrease is observed in the AP-SiO₂-based system because of the severe agglomeration of nanoparticles. By contrast, the AM-SiO₂ and SU-SiO₂ form the regular particle network structure and accelerate the salt dissociation in electrolytes, thereby providing an effective ion transport pathway and more mobile ions for conduction, respectively. Consequently, the composite systems with AM-SiO₂ and SU-SiO₂ deliver remarkable enhancement in the ion transport properties.

Enhancing the Efficiency of a Dye-Sensitized Solar Cell Based on a Metal Oxide Nanocomposite Gel Polymer Electrolyte

To overcome the critical limitations of liquid-electrolyte-based dye-sensitized solar cells, quasi-solid-state electrolytes have been explored as a means of addressing long-term device stability, albeit with comparatively low ionic conductivities and device performances. Although metal oxide additives have been shown to augment ionic conductivity, their propensity to aggregate into large crystalline particles upon high-heat annealing hinders their full potential in quasi-solid-state electrolytes. In this work, sonochemical processing has been successfully applied to generate fine Co₃O₄ nanoparticles that are highly dispersible in a PAN:P(VP-co-VAc) polymer-blended gel electrolyte, even after calcination. An optimized nanocomposite gel polymer electrolyte containing 3 wt % sonicated Co₃O₄ nanoparticles (PVVA-3) delivers the highest ionic conductivity (4.62 × 10^-3 S cm^-1) of the series. This property is accompanied by a 51% enhancement in the apparent diffusion coefficient of triiodide versus both unmodified and unsonicated electrolyte samples. The dye-sensitized solar cell based on PVVA-3 displays a power conversion efficiency of 6.46% under AM1.5 G, 100 mW cm^-2. By identifying the optimal loading of sonochemically processed nanoparticles, we are able to generate a homogenous extended particle network that effectively mobilizes redox-active species through a highly amorphous host matrix. This effect is manifested in a selective 51% enhancement in photocurrent density (J_SC = 16.2 mA cm^-2) and a lowered barrier to N719 dye regeneration (R_CT = 193 Ω) versus an unmodified solar cell. To the best of our knowledge, this work represents the highest known efficiency to date for dye-sensitized solar cells based on a sonicated Co₃O₄-modified gel polymer electrolyte. Sonochemical processing, when applied in this manner, has the potential to make meaningful contributions toward the ongoing mission to achieve the widespread exploitation of stable and low-cost dye-sensitized solar cells.

Progress on Electrolytes Development in Dye-Sensitized Solar Cells

Dye-sensitized solar cells (DSSCs) have been intensely researched for more than two decades. Electrolyte formulations are one of the bottlenecks to their successful commercialization, since these result in trade-offs between the photovoltaic performance and long-term performance stability. The corrosive nature of the redox shuttles in the electrolytes is an additional limitation for industrial-scale production of DSSCs, especially with low cost metallic electrodes. Numerous electrolyte formulations have been developed and tested in various DSSC configurations to address the aforementioned challenges. Here, we comprehensively review the progress on the development and application of electrolytes for DSSCs. We particularly focus on the improvements that have been made in different types of electrolytes, which result in enhanced photovoltaic performance and long-term device stability of DSSCs. Several recently introduced electrolyte materials are reviewed, and the role of electrolytes in different DSSC device designs is critically assessed. To sum up, we provide an overview of recent trends in research on electrolytes for DSSCs and highlight the advantages and limitations of recently reported novel electrolyte compositions for producing low-cost and industrially scalable solar cell technology.

A low molecular mass organogelator electrolyte with TiO2 nanoparticles for stable and efficient quasi-solid-state dye sensitized solar cells

We report stable and efficient quasi-solid-state dye-sensitized solar cells (QS-DSSCs) fabricated using a combination of TiO₂ nanoparticles and a low-molecular-mass organogelator (LMOG) as a nanoparticle–gel composite electrolyte.