Photovoltaic characteristics of natural light harvesting dye sensitized solar cells

Simple and Fast Microwave-Assisted Synthesis Methods of Nanocrystalline TiO2 and rGO Materials for Low-Cost Metal-Free DSSC Applications

Nanocrystalline TiO2 and reduced graphene oxide (rGO) materials have been synthesized by a simple and low-cost microwave-assisted hydrothermal method and applied in dye-sensitized solar cells (DSSCs) as photoactive and metal-free counter electrodes, respectively. Different TiO2 nanocrystalline materials have been synthesized via the acid hydrolysis sol-gel method, followed by microwave hydrothermal treatment at 210 °C and 300 psi and at different microwave irradiation times (20, 30, 45, and 60 min) instead of the usual hydrothermal time of 12 h. The properties of the produced mesoporous nanocrystalline TiO2 are investigated in terms of their morphology, crystal structure, optical properties, and surface area behavior using relevant characterization techniques. Maximum specific surface area values (S BET) of 97.77 and 100.7 m2 g-1 are measured for TiO2, with the average crystallite sizes of 18.6 and 17.5 nm, at microwave irradiation times of 30 and 45 min, respectively. Different rGO samples have been prepared by the modified Hummers method, followed by microwave-assisted reduction at a temperature of 200 °C and pressure of 300 psi at different microwave irradiation times (3, 17, and 25 min). The physicochemical properties of the different rGO samples in terms of morphology, crystallization, and optical properties are characterized by TEM, XRD, and Raman spectroscopic analysis. The current density J sc of the fabricated DSSCs based on TiO2 as the photoelectrode and rGO as the counter electrode compared with DSSCs based on Pt as the counter electrode is found to be 11.25 and 9.28 mA cm-2, respectively. Although the overall power efficiency of the fabricated DSSCs based on rGO as the counter electrode is lower than that based on the Pt electrode, the former still exhibits promising prospects for replacing Pt with low-cost metal-free carbon-based DSSCs.

Thin Film Fabrication by Pulsed Laser Deposition from TiO2 Targets in O2, N2, He, or Ar for Dye-Sensitized Solar Cells

Active semiconductor layers of TiO2 were synthesized via pulsed laser deposition in He, N2, O2, or Ar to manufacture DSSC structures. As-prepared nanostructured TiO2 coatings grown on FTO were photosensitized by the natural absorption of the N719 (Ruthenium 535-bis TBA) dye to fabricate photovoltaic structures. TiO2 photoanode nanostructures with increased adsorption areas of the photosensitizer (a combination with voluminous media) were grown under different deposition conditions. Systematic SEM, AFM, and XRD investigations were carried out to study the morphological and structural characteristics of the TiO2 nanostructures. It was shown that the gas nature acts as a key parameter of the architecture and the overall performance of the deposited films. The best electro-optical performance was reached for photovoltaic structures based on TiO2 coatings grown in He, as was demonstrated by the short-circuit current (Isc) of 5.40 mA, which corresponds to the higher recorded roughness (of 44 ± 2.9 nm RMS). The higher roughness is thus reflected in a more efficient and deeper penetration of the dye inside the nanostructured TiO2 coatings. The photovoltaic conversion efficiency (η) was 1.18 and 2.32% for the DSSCs when the TiO2 coatings were deposited in O2 and He, respectively. The results point to a direct correlation between the electro-optical performance of the prepared PV cells, the morphology of the TiO2 deposited layers, and the crystallinity features, respectively.

Advances on Dye-Sensitized Solar Cells (DSSCs) Nanostructures and Natural Colorants: A Review

Human beings are attempting to take advantage of renewable natural resources by using solar cells. These devices take the sun’s radiation and convert it into electrical energy. The issue with traditional silicon-based solar cells is their manufacturing costs and environmental problems. For this reason, alternatives have been developed within the solar cell field. One of these alternatives is the dye-sensitized solar cell (DSSC), also known as Grätzel solar cells. DSSCs are a type of solar cell that mimics photosynthesis. They have a photoanode, which is formed by a semiconductor film sensitized with a dye. Some of their advantages include low-cost manufacturing, eco-friendly materials use, and suitability for most environments. This review discusses four important aspects, with two related to the dye, which can be natural or synthetic. Herein, only natural dyes and their extraction methods were selected. On the other hand, this paper discusses the nanostructures used for DSSCs, the TiO2 nanostructure being the most reported; it recently reached an efficiency level of 10.3%. Finally, a review on the novelties in DSSCs technology is presented, where it is observed that the use of Catrin protein (cow brain) shows 1.45% of efficiency, which is significantly lower if compared to Ag nanoparticles doped with graphene that report 9.9% efficiency.

Enhanced Biophotocurrent Generation in Living Photosynthetic Optical Resonator

Bioenergy from photosynthetic living organisms is a potential solution for energy-harvesting and bioelectricity-generation issues. With the emerging interest in biophotovoltaics, extracting electricity from photosynthetic organisms remains challenging because of the low electron-transition rate and photon collection efficiency due to membrane shielding. In this study, the concept of "photosynthetic resonator" to amplify biological nanoelectricity through the confinement of living microalgae (Chlorella sp.) in an optical micro/nanocavity is demonstrated. Strong energy coupling between the Fabry-Perot cavity mode and photosynthetic resonance offers the potential of exploiting optical resonators to amplify photocurrent generation as well as energy harvesting. Biomimetic models and living photosynthesis are explored in which the power is increased by almost 600% and 200%, respectively. Systematic studies of photosystem fluorescence and photocurrent are simultaneously carried out. Finally, an optofluidic-based photosynthetic device is developed. It is envisaged that the key innovations proposed in this study can provide comprehensive insights in biological-energy sciences, suggesting a new avenue to amplify electrochemical signals using an optical cavity. Promising applications include photocatalysis, photoelectrochemistry, biofuel devices, and sustainable optoelectronics.

Theoretical insights on the comparison of champion dyes SM315 and C275 used for DSSCs reaching over 12% efficiency and the further optimization of C275

Theoretical insights on the comparison between the champion dyes SM315 and C275 used for high-performance dye-sensitized solar cells (DSSCs) reaching over 12% efficiency with different electron donors only (porphyrin for SM315 and indenoperylene for C275) were explored for the first time. The intrinsic reasons for the significantly improved monochromatic photon-to-electric current conversion efficiency (IPCE) and open circuit voltage (V_oc) of C275-based DSSCs over those of SM315 were revealed. According to our results, we find that the larger IPCE of C275 is attributed to its larger electronic coupling, smaller reorganization energy, reduced exciton binding energy and enhanced charge transfer character, all of which when combined lead to a larger electron injection efficiency. In addition, the larger V_oc of C275 is due to a greater number of injected electrons, a smaller molecular volume and a smaller projected area, which lead to a more compact adsorption layer with a hindered charge recombination process. Thus, C275 is expected to have more potential to further optimize high-performance DSSCs. In view of the primary shortcoming of C275, which is its relatively narrow absorption spectrum, further optimization was made through structural modification using a series of heterocyclic anchoring groups. Using the same evaluation criteria, the theoretical screening of these dyes based on C275 is carried out. We find that indenoperylene dye with a barbituric acid (BA) anchoring group is a promising candidate for the experimental synthesis of high-performance DSSCs with improved J_sc, V_oc and adsorption stability.

Photovoltaic and spectroscopic characteristics of perovskite/TiO2 heterostructure photoanodes for improving the efficiency of dye sensitized solar cells

Perovskite-type ternary oxide nanostructured materials have gained great attention in recent years as promising materials for solar cell applications. However these ternary oxides have failed to be applied as a working electrode in DSSCs due to its poor performance and its inability to bind dye molecules to the surface. A heterostructure perovskite/TiO₂ photoactive electrodes is a new strategy to improve the photon-to-current efficiency (PCE) of DSSCs. In this paper, BaZrO₃ (BZ), BaTiO₃ (BT) and nanocomposite [1:1] molar% from BaTiO₃-BaZrO₃ perovskite nanostructured materials synthesized via sonochemical sol-gel methods, are coated on the top of the TiO₂ photoactive electrode. This heterostructured (perovskite/TiO₂) photoelectrode has been applied for improving the performance of dye-sensitized solar cells (DSSCs). The crystallographic, morphological and optical characteristics of the different prepared perovskite nanomaterials has been investigated by XRD, SEM, TEM, Raman and UV-Vis Diffuse reflectance spectroscopic analysis, respectively. Dye-sensitized solar cells based on the different heterostructure perovskite/TiO₂ electrodes are assembled, and high conversion efficiency (η) are calculated from the current density-voltage (J-V) characteristics of the solar cells. The results show an efficiency enhancement with about ∼22%, 37% and 51% in case of BZ, BTZ and BT respectively. These enhancements is attributed to high refractive index of the perovskite nanoparticles, higher incident photon-to-current conversion yield which is due to greater fraction of light scattered, as well as the less recombination of the photogenerated electrons.