A system for the production of hybrid photovoltaic devices using Mo-doped TiO2 / rGO as a nanocomposite and natural pigments as sensitizers

Abstract

A system for the production of dye-sensitized solar cells (DSSCs), consisting of: a) a nanocomposite manufacturing unit configured for the synthesis of (MoxTi1-2xO2-δ)1-y(RGO)y nanocomposites, wherein x is in the range of 0.5 to 3.0 mol% and y is 0.75 wt%; b) a substrate deposition unit configured to deposit the nanocomposites onto an FTO substrate using a binder-free doctor blade mechanism; c) a sensitization unit configured to apply sensitizers from the group of natural pigments, including betalain, anthocyanin, curcumin and lawsone; d) an electrode assembly unit for constructing a sandwich DSSC structure; and e) a photovoltaic power measurement unit for carrying out IV and IPCE measurements under solar irradiation.

Description

FIELD OF THE INVENTION

[0001] The present disclosure relates to a system for producing dye-sensitized solar cells (DSSCs) using Mo-doped TiO2 / RGO nanocomposites and natural pigment sensitizers. BACKGROUND OF THE INVENTION

[0002] Dye-sensitized solar cells (DSSCs) have emerged as a promising alternative to conventional solar technologies, offering advantages in terms of stability, reasonable cost, and lower toxicity. Two fundamental components are crucial to the performance of DSSCs: the semiconducting photoanode material and the sensitizing dyes.

[0003] Replacing metal ions in semiconductor materials has proven to be a crucial strategy for improving optoelectronic properties in various applications, including solar energy conversion, catalysis, sensing, and electronics. Systematic modification of the host lattice can significantly improve the overall device performance.

[0004] The following challenges need to be addressed: improving the performance of the photoanode material through strategic doping with metal ions and exploring sustainable, cost-effective alternatives to conventional sensitizing dyes.

[0005] To address the above-mentioned challenges, the present invention provides a system for fabricating dye-sensitized solar cells (DSSCs) using Mo-doped TiO2 / RGO nanocomposites and natural pigment sensitizers. The invention aims to improve the efficiency of solar energy conversion while promoting the sustainability of photovoltaic technology, potentially opening new avenues for more accessible and environmentally friendly solar energy solutions. SUMMARY OF THE INVENTION

[0006] The present disclosure relates to a system for fabricating dye-sensitized solar cells (DSSCs) with Mo-doped TiO2 / RGO nanocomposites and natural pigment sensitizers. This invention presents a system for fabricating dye-sensitized solar cells (DSSCs) by developing Mo(VI)-doped TiO2 / RGO nanocomposites with natural pigment sensitizers. The invention introduces a system for modifying semiconductor materials by inserting Mo(VI) ions into the TiO2 host lattice, coupled with RGO incorporation, to improve optoelectronic properties. The nanocomposites are prepared using an in situ sol-gel mechanism and tested with both synthetic N719 dye and natural pigments (betalain, anthocyanin, curcumin, and lawsone). The photovoltaic performance showed that the optimized (Mo 0.100 Ti 0.980 O 1.990 ) 0.925 (RGO) 0.075Nanocomposite showed improved photovoltaic performance, achieving an efficiency of 7.58% with the dye N719 and 2.23% with betalain, demonstrating the potential of using natural, sustainable sensitizers in solar energy conversion.

[0007] The present disclosure is intended to provide a system for manufacturing dye-sensitized solar cells (DSSCs). The system comprises: a nanocomposite manufacturing unit configured to produce (Mo x Ti 1-2x O 2-6 ) 1-y (RGO) yNanocomposites are synthesized, where x is between 0.5 and 3.0 mol% and y is 0.75 wt%; a substrate deposition unit configured to deposit the nanocomposites onto an FTO substrate using a binder-free doctor blade mechanism; a sensitization unit configured to apply sensitizers from the group of natural pigments, including betalain, anthocyanin, curcumin, and lawsone; an electrode assembly unit for constructing a sandwich DSSC structure; and a photovoltaic power measurement unit for performing IV and IPCE measurements under solar irradiation.

[0008] An object of the present disclosure is to provide a system for fabricating dye-sensitized solar cells (DSSCs) with Mo-doped TiO2 / RGO nanocomposites and natural pigment sensitizers.

[0009] Another objective of the present disclosure is the development of a novel nanocomposite system of Mo-doped TiO2 / RGO with improved optoelectronic properties for dye-sensitized solar cell applications.

[0010] Another objective of the present disclosure is to provide an alternative approach to semiconductor modification by precise metal ion substitution to improve photovoltaic performance.

[0011] Another objective of the present disclosure is to explore sustainable natural pigments as cost-effective and environmentally friendly alternatives to conventional synthetic dyes in solar cell sensitization.

[0012] Another objective of the present disclosure is to demonstrate the potential of in situ sol-gel synthesis for the preparation of advanced nanocomposite materials with tunable optoelectronic properties.

[0013] Another objective of the present disclosure is to improve charge transfer and electron lifetime in semiconductor-based photovoltaic devices.

[0014] Another objective of the present disclosure is to reduce the environmental and economic barriers associated with conventional dye-sensitized solar cell technologies by using natural, readily available pigment sources.

[0015] To further clarify the advantages and features of the present disclosure, a more detailed description of the invention will be given with reference to specific embodiments thereof, which are illustrated in the accompanying drawings. It should be noted that these drawings represent only typical embodiments of the invention and are therefore not to be considered limiting its scope. The invention will be described and explained in additional detail and in greater detail with reference to the accompanying drawings. SHORT DESCRIPTION OF THE FIGURE

[0016] These and other features, aspects, and advantages of the present disclosure will be better understood when the following detailed description is read with reference to the accompanying drawings, in which like characters represent like parts throughout. Where: Fig. 1 shows a block diagram of a system for manufacturing dye-sensitized solar cells (DSSCs) according to an embodiment of the present disclosure.

[0017] Furthermore, those skilled in the art will appreciate that elements in the drawings are shown for convenience and may not necessarily be drawn to scale. For example, the flowcharts illustrate the method by key steps to enhance understanding of aspects of the present disclosure. Furthermore, with respect to device construction, one or more components of the device may have been represented in the drawings by conventional symbols, and the drawing may show only the specific details relevant to understanding embodiments of the present disclosure in order not to clutter the drawings with details that would be readily apparent to those skilled in the art who would benefit from the description herein. DETAILED DESCRIPTION:

[0018] To facilitate an understanding of the principles of the invention, reference will now be made to the embodiment illustrated in the drawings and described in specific language. It is to be understood, however, that no limitation on the scope of the invention is intended thereby, since such changes and further modifications of the illustrated system, and such further applications of the principles of the invention as illustrated therein, are contemplated as would normally occur to one skilled in the art to which the invention pertains.

[0019] It will be understood by one skilled in the art that the foregoing general description and the following detailed description are exemplary and explanatory of the invention and are not intended to be limiting thereof.

[0020] References in this specification to "one aspect," "another aspect," or similar language mean that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present disclosure. Therefore, occurrences of the phrase "in one embodiment," "in another embodiment," and similar language throughout this specification may or may not all refer to the same embodiment.

[0021] The terms "comprises," "comprising," or other variations thereof are intended to cover non-exclusive inclusion, such that a process or method comprising a list of steps not only includes those steps, but may also include other steps not expressly listed or inherent in such process or method. Likewise, one or more devices or subsystems or elements or structures or components preceded by "comprises...a" does not preclude, without further limitation, the existence of other devices or other subsystems or other elements or other structures or other components or additional devices or additional subsystems or additional elements or additional structures or additional components.

[0022] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The system, methods, and examples provided herein are for illustrative purposes only and should not be considered limiting.

[0023] Embodiments of the present disclosure will be described in detail below with reference to the accompanying drawings.

[0024] Fig. 1 shows a block diagram of a system (100) for manufacturing dye-sensitized solar cells (DSSCs) according to an embodiment of the present disclosure.

[0025] With reference to Fig.1, the system (100) comprises: a nanocomposite manufacturing unit (102) configured to synthesize (MoxTi1-2xO2-δ)1-y(RGO)y nanocomposites, where x is in the range of 0.5 to 3.0 mol% and y is 0.75 wt%; a substrate deposition unit (104) configured to deposit the nanocomposites on an FTO substrate using a binder-free doctor blade mechanism; a sensitization unit (106) configured to apply sensitizers selected from the group of natural pigments, including betalain, anthocyanin, curcumin, and lawsone; an electrode assembly unit (108) for constructing a sandwich DSSC structure; and a photovoltaic performance measurement unit (110) for performing IV and IPCE measurements under solar irradiation.

[0026] In one embodiment, the nanocomposite production unit (102) comprises: a sol-gel synthesis mechanism (102a) for the in-situ chemical production of (Mo x Ti 1-2x O 2-δ ) 1-y (RGO) y -Nanocomposites, wherein TiO 2 is modified with different compositions of Mo(VI) as a dopant and then additionally doped TiO 2 nanoparticles are incorporated on the surface of RGO to improve the optoelectric properties of the composite material; a dopant insertion mechanism (102b) for incorporating Mo(VI) ions into the TiO 2 host lattice; and an RGO integration mechanism (102c) for surface incorporation of RGO.

[0027] In one embodiment, the substrate deposition unit (104) comprises: a binderless doctor blade mechanism (104a) for uniformly depositing nanocomposites; a temperature-controlled substrate holding platform (104b); and a precision distribution mechanism (104c) for producing a uniform film thickness.

[0028] In one embodiment, the sensitization unit (106) is configured to sensitize the nanoparticle-coated FTO substrate through controlled adsorption mechanisms, wherein the natural pigments are extracted from botanical sources and processed and purified prior to application.

[0029] In one embodiment, the fabricated nanoparticles deposited on the FTO substrate are also sensitized with N719 dyes as a model protocol to perform a performance comparison with natural pigments.

[0030] In one embodiment, the electrode assembly unit (108) is configured to include the sensitized photoelectrodes for fabricating DSSCs with a counter electrode.

[0031] In one embodiment, the fabricated DSSC device structure consists of a sensitized TiO2 layer sandwiched between a platinum-coated counter electrode and a reduced graphene oxide (RGO) / TiO2 coated FTO glass substrate, using an electrolyte containing I3-I3I - to facilitate cargo transport.

[0032] In one embodiment, the photovoltaic power measuring unit (110) is configured to measure a solar irradiance of 100 mW / cm 2to provide IV characteristic measurements, to perform incident photon-to-current efficiency (IPCE) measurements, and to compare the power conversion efficiencies of different nanocomposite and sensitizer configurations.

[0033] The present invention relates to a system for producing dye-sensitized solar cells (DSSC) with Mo-doped TiO 2 / RGO nanocomposites and natural pigment sensitizers. The system is configured such that first a series of (Mo x Ti 1-2x O 2-δ ) 1-y (RGO) y[x = 0.5 to 3.0 mol%; y = 0.75 wt%] NCs are synthesized, and the prepared nanocomposites are then deposited onto the FTO substrate using a binder-free doctor blade mechanism. The deposited substrate is sensitized with N719 dyes and natural pigments. The sensitized substrates are used to fabricate electrodes, which are then subjected to photovoltaic studies to evaluate their photovoltaic performance.

[0034] The TiO2 material is modified by incorporating different compositions of Mo(VI) as a dopant, and the doped TiO2 nanoparticles are subsequently integrated into the surface of RGO to enhance the optoelectronic properties of the composite. The inclusion of Mo(VI) ions can alter the TiO2 host lattice through three possible mechanisms: substitution of Ti(IV) ions with Mo(VI) ions, integration of Mo(VI) ions as interstitial sites into the TiO2 lattice, or formation of mixed metal oxides with TiO2. The ionic radius of Mo(VI) ions (0.79 Å) is slightly larger than that of Ti(IV) ions (0.74 Å), but it fits into the TiO2 lattice by introducing density of states (DOS) between the valence and conduction bands of the host lattice. This makes Mo(VI) an effective dopant for modifying the optoelectronic behavior of TiO2.Compared to pure TiO2 or binary composites such as TiO2 / RGO and TiO2 / CNTs, the optoelectronic and photovoltaic properties of the composite (MoxTi1-2×O2-δ)1-y(RGO)y remain underexplored. Carbon nanostructures such as carbon nanotubes (CNTs) or reduced graphene oxide (RGO) are widely used as support materials in energy harvesting systems due to their ability to enhance the properties of the host materials. In studies with binary TiO2 / RGO nanocomposites, DSSCs have achieved efficiencies of up to 5.98% and 4.76% when optimized TiO2 / RGO composites (0.75 wt%) were sensitized with the dyes N719 and N3, respectively. The incorporation of TiO2 with RGO in photovoltaic devices has also been highlighted in the literature. Despite these advances, however, the reported efficiencies of these systems remain lower compared to conventional silicon-based solar cells and the newer perovskite solar cells.

[0035] In dye-sensitized solar cells (DSSCs), the sensitizing dye plays a crucial role in initiating photochemical conversions, in addition to modifying semiconductor materials. Sensitizers such as Ru(II) dyes, quantum dots (QDs), and QD-dye hybrids are widely used to capture the maximum photon flux from the solar spectrum. While these sensitizers are effective in converting solar energy into electrical energy, they suffer from several limitations, including high cost, environmental concerns, photo- and thermal stability issues, and challenges related to their compatibility with the photoactive material.

[0036] To overcome challenges related to cost, sustainability, and the lack of metal-based sensitizers, natural pigment-based dyes have attracted considerable interest due to their intense absorption properties in the UV-visible / near-infrared region of the solar spectrum. These dyes are derived from leaves, flowers, seeds, and fruits, are easily extracted using simple methods, and possess functional groups that enable effective interconnectivity between photoactive materials and efficient charge transfer from the oxidized dyes to the LUMO of TiO2 in dye-sensitized solar cells (DSSCs).Studies have shown that TiO2-based photoelectrodes sensitized with betalain, a natural pigment, achieve improved light-harvesting capabilities and photovoltaic properties. A power conversion efficiency of 3.0% was observed at a photoelectrode film thickness of 7 µm and 80% aggregation of the betalain dye on the photoelectrode surface. Higher dye aggregation was found to broaden the absorption spectrum, thus increasing electron injection and collection efficiency compared to the adsorption of monomeric dyes. Similarly, humic acid extracted from soil was used as a natural sensitizer in TiO2-based DSSCs and achieved a power conversion efficiency of 2.4% when co-adsorbed with chenodeoxycholic acid under 0.5 solar irradiation, compared to 1.4% efficiency for humic acid alone under 1 solar irradiation.These advances in sensitization with natural dyes typically involved bare TiO2 surfaces, which can limit proper charge separation in DSSCs. To further improve conversion efficiency, the development of (Mo . x Ti 1-2x O 2-δ ) 1-y (RGO) y- Composites are proposed that allow the tuning of optoelectric properties and subsequent sensitization with sustainable natural dyes.

[0037] In one embodiment, a simple in situ sol-gel mechanism is used to synthesize (Mo x Ti 1-2x O 2-δ ) 1-y (RGO) yNanocomposites (NCs) with different Mo(VI) doping concentrations ranging from 0.5 to 3.0 mol% were used. The optoelectronic properties of these NCs are compared with binary TiO2 / RGO nanocomposites in the context of photovoltaic performance. The binder-free nanocomposites are deposited on FTO substrates and sensitized with natural pigments, including betalain from beetroot (Beta vulgaris), anthocyanin from black grapes (Vitis vinifera), curcumin from turmeric (Curcuma longa L.), and lawsone from henna leaves (Lawsonia inermis). These natural pigments act as sensitizers for the fabrication of sandwich dye-sensitized solar cells (DSSCs). The energy conversion performance of the (MoxTil-2xO2-δ)1 -y(RGO)y nanocomposites is first evaluated using the N719 dye, followed by tests with the natural dyes. This system emphasizes the chemical connection between the nanocomposite-based photoelectrodes and the natural pigments.Finally, the sensitized photoelectrodes are assembled with a counter electrode to complete the DSSC structure, and the photovoltaic performance is measured by IV and IPCE measurements under standard sun conditions (100 mW / cm). 2 ) analyzed.

[0038] The prepared nanocomposites are subjected to characterization including X-ray diffraction (XRD), Raman spectroscopy, UV-visible diffuse reflectance spectroscopy, X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM) with high-resolution time-resolved photoluminescence spectroscopy (TRPL), electrochemical impedance spectroscopy, FTIR and UV-visible absorption spectroscopy, and many others.

[0039] The crystal structure and phase purity of the materials synthesized with Mo(VI) doping in the TiO2 host lattice of TiO2 / RGO nanocomposites (NCs) were confirmed by powder X-ray diffraction (XRD) analysis. The XRD profiles for bare TiO2 nanoparticles, TiO2 / RGO NCs, and (MoxTi1-2xO2-δ)1-y(RGO)y NCs with different Mo(VI) doping levels (0.5 to 3.0 mol%) exhibit peak positions at approximately 25.29° (101), 37.81° (004), 47.90° (200), and other reflections corresponding to the anatase phase of TiO2, which is consistent with PCPDFWIN No. 21-1272. No additional peaks were observed for the TiO2 host lattice or the RGO component, suggesting that the prepared NCs retain the anatase phase without the formation of mixed phases or metal oxides. The absence of pronounced RGO peaks is attributed to the low content or potential shielding by the anatase structure.The results further confirm that Mo(VI) ions replace Ti(IV) ions without changing the phase purity.

[0040] The addition of Mo(VI) doping increased the crystal size from 9.31 nm to 13.52 nm, as determined by Scherer's formula, and slightly increased the cell volume from 135.59 Å 3 to 136.88 Å 3This increase in size is likely due to the larger ionic radius of Mo(VI) (0.79 Å) compared to Ti(IV) (0.74 Å). Structural parameters, including lattice constants "a" and "c", crystal size, and lattice strain, were calculated, and shifts in peak positions and intensity fluctuations were observed with increasing Mo(VI) content. These changes were analyzed using Rietveld refinement, which confirmed the replacement of Ti(IV) by Mo(VI) and the absence of interstitial defects or mixed oxides. The refinement results, including cell parameters and Rietveld factors, are consistent with the XRD data and further confirm the tetragonal anatase crystal structure of the NCs. The refinement quality values ​​(χ 2 ) ranged between 1.38 and 1.51, indicating an excellent fit.

[0041] Visualization of the crystal structures using VESTA confirmed the tetragonal anatase phase for all NCs. Although minor distortions in the lattice were observed, these were attributed to the substitution of Ti(IV) with Mo(VI), resulting in changes in the Ti-O bond lengths and Ti-O-Ti bond angles. No evidence of mixed oxides or interstitial defects was found, and the data suggest that the substitution of two Ti(IV) ions with one Mo(VI) ion can create oxygen vacancies in the lattice. Overall, the structural integrity and phase purity of the NCs were maintained after doping, with minimal crystal defects. These findings were supported by a quantitative analysis of the lattice parameters, bond angles, and bond lengths, demonstrating the compatibility of the Mo(VI) doping within the TiO2 host lattice.

[0042] The structural properties of the Mo(VI)-doped nanocomposites (NCs) in TiO2 / RGO were analyzed by Raman spectroscopy. The Raman spectra showed characteristic peaks of the tetragonal anatase crystal structure of TiO2 at 146.34, 397.8, 520.40, and 639.04 cm -1 , corresponding to the vibrational modes Eg, B1g, Alg, and Eg (1), respectively. Additionally, D and G bands at 1354.80 and 1583.41 cm -1 the presence of ordered and disordered graphitic carbon. With the introduction of Mo(VI) doping, a decrease in the intensity ratio (ID / IG) from 0.872 to 0.835 was observed, along with a slight shift of the characteristic peaks to higher frequencies (147.89, 401.91, 521.61, and 640.24 cm -1) and a reduced peak intensity. These changes were attributed to strain gradients caused by Mo(VI) integration and an increase in crystallite size. The absence of additional peaks indicated that the NCs were free of mixed phases such as molybdenum or other TiO2 phases such as rutile and brookite.

[0043] The optical properties were investigated using UV-visible diffuse reflectance spectroscopy. With increasing Mo(VI) doping content, the absorption edge of the TiO2 / RGO NCs shifted to higher wavelengths (visible range) with improved absorption strength in the UV-visible spectrum. This behavior was attributed to the Mo(VI) 4f states, which reduced the conduction band edge of TiO2 and acted as charge traps, thereby improving charge separation. These improvements enabled better coverage of the solar spectrum, making the ternary NCs more efficient for solar energy harvesting. The optical energy band gap decreased from 2.87 eV for TiO2 / RGO to 2.64 eV for the optimized (Mo 0.100 Ti 0.980 O 1.990 ) 0.925 (RGO) 0.075 NC, indicating improved optoelectronic properties due to Mo(VI) doping.

[0044] The functional properties were further investigated using FTIR spectroscopy (data in the Supplementary Information) and XPS analysis. The XPS survey spectrum of the optimized NC confirmed the presence of Ti, O, C, and Mo without any other elemental impurities. High-resolution XPS of the Ti2p core levels before and after Mo(VI) doping showed peak shifts toward higher binding energies (from 2.71 to 2.79 eV), reflecting changes in the electronic states upon doping. These results underline the positive effects of Mo(VI) doping on structural and optoelectronic properties and improve the material's performance for photovoltaic applications. The results show that the interaction between different metals and lattice oxygen (Ti-O-Mo) indicates the substitution of Ti(IV) by Mo(VI) ions in the (Mo0.100Ti0.98001.990)0.925(RGO)0.075 nanocomposites (NCs).The high-resolution core-level XPS spectrum shows a main peak at 530.41 eV corresponding to lattice oxygen (Ti-O), which further splits into four peaks at 529.85 eV, 530.89 eV, 531.34 eV, and 532.52 eV. These peaks are attributed to mixed metals consisting of lattice oxygen, Ti-O-Ti, Ti-OC, and carbonic acid forms of lattice oxygen (CO). The high-resolution C1s XPS spectrum shows four deconvoluted peaks at binding energies of 284.57, 285.49, 286.40, and 288.0 eV, corresponding to elemental carbon units such as O-Ti-C, sp2-bonded (CC), CO, and Ti-OC, thus confirming the incorporation of reduced graphene oxide (RGO) with Mo(VI)-doped TiO2. Likewise, the Mo3d XPS spectrum exhibits two peaks at 232.37 and 235.14 eV, corresponding to Mo3d5 / 2 and Mo3d3 / 2, respectively, with a binding energy difference of 2.77 eV, thus confirming the presence of Mo in the +6 oxidation state and its insertion into the TiO2 lattice.

[0045] Transmission electron microscopy (TEM) reveals that spherical nanostructured grains of TiO2 and Mo-doped TiO2 are evenly distributed on the RGO sheet. After Mo(VI) doping, the particle size increases from 13 nm to 17 nm, corresponding to the larger ionic radius of Mo(VI). High-resolution TEM images reveal well-defined crystal edges corresponding to the d-spacing values ​​of the (101) reflection of anatase phase TiO2. The observed unclear crystal edges indicate strong chemical grafting between doped / undoped TiO2 and RGO. Selected area electron diffraction (SAED) patterns show well-defined rings with lattice points, confirming the crystalline nature of the NCs and their alignment with the d-spacing values ​​of the anatase phase reflections.

[0046] Time-resolved photoluminescence spectroscopy (TRPL) shows that the introduction of Mo(VI) doping into TiO2 / RGO increases the average excited-state electron lifetime from 13.8 ps to 48.80 ps, ​​as reflected in the fitted TRPL decay parameters. This increase in lifetime confirms the replacement of two Ti(IV) ions by one Mo(VI) ion, leading to an increased carrier density. The results demonstrate that Mo(VI) doping improves the optoelectronic properties of TiO2 / RGO NCs, particularly through increased electron lifetime and carrier density, thus highlighting the potential for improved energy conversion applications. The results indicate that the replacement of two Ti(IV) ions with a single Mo(VI) ion increases the carrier density of the material and creates charge-trapping sites that facilitate charge separation. This improvement improves charge carrier transport in the DSSCs.However, when the Mo(VI) doping concentration in the TiO2 / RGO nanocomposites increases from 1.0 mol% to 3.0 mol%, the average exciton lifetime decreases from 48.80 ps to 17.30 ps. This suggests that higher doping concentrations negatively affect charge transport, as the increased dopant content also creates more charge traps that promote charge recombination and thereby degrade the overall performance.

[0047] The charge transfer process and resistance of TiO2 / RGO nanocomposites (NCs) before and after Mo(VI) doping were analyzed using electrochemical impedance spectroscopy (EIS). Nyquist plot data for both TiO2 / RGO and (Mo0.100Ti0.980O1.990)0.925(RGO)0.075NCs, measured over a frequency range of 0.1 Hz to 1.2 MHz, revealed this, including ohmic resistance (Ro) and charge-transfer resistance (Rct). The results show that the charge-transfer resistance decreases from 79.22 Ω to 49.27 Ω after Mo(VI) doping, while the ohmic resistance values ​​for the individual materials are 12.70 Ω and 10.97 Ω, respectively. This reduction in charge transfer resistance indicates a reduction in electron-hole recombination under solar irradiation in DSSCs, suggesting improved charge carrier separation in photovoltaic devices.In addition, the adsorption and desorption properties of dyes are investigated; the corresponding results can be found in the supplementary information.

[0048] The effect of Mo(VI) doping in TiO2 / RGO nanocomposites (NCs) on the photovoltaic performance of dye-sensitized solar cells (DSSCs) is investigated. When Mo(VI) is introduced at a low concentration (0.5 mol%), the short-circuit current (Jsc) increases significantly from 16,180 to 18,081 mA / cm 2 and reaches a peak value of 19,656 mA / cm 2for the optimized NCs. This improvement in Jsc is attributed to the Mo(VI) doping, which acts as charge-trapping sites, aids in electron collection, and improves charge transfer from the RGO surface to the counter electrode. The doping also expands the optical absorption range and contributes to a better photon flux for solar conversion. However, increasing the Mo(VI) doping to 3.0 mol% results in a reduction in Jsc to 17,841 mA / cm 2 .

[0049] Regarding the open circuit voltage (Voc), Mo(VI) doping slightly improves the Voc value, from 720 mV for TiO2 / RGO NCs to 740 mV for the optimized (Mo 0.100 Ti 0.980 O 1.990) 0.925 (RGO) 0.075NCs. However, excessive doping reduces the Voc to 690 mV, indicating that too much Mo(VI) impedes charge transport and increases device resistance. The fill factor (FF) also experiences minimal improvement, increasing from 49.87% to 52.22% for the optimized sample, but then decreases to 48.70% at higher doping concentrations.

[0050] The greatest improvement is in the efficiency (η). It increases from 5.81% for TiO2 / RGO NCs to 6.89% at a doping concentration of 1.0 mol% and reaches a peak value of 7.58% at a doping concentration of 2.0 mol%, representing an increase of 30.46% over the baseline TiO2 / RGO NCs. However, further doping beyond this optimal point leads to a decrease in efficiency, with the highest doping concentration (3.0 mol%) reducing the efficiency to 5.99%. The results indicate that Mo(VI) doping enhances the performance up to a certain concentration, above which excessive doping negatively affects the photovoltaic properties of the DSSCs.

[0051] The highest photovoltaic performance was achieved at Mo 0.0 @Ti 99.0R NC was observed, which exhibited a lower optical energy band gap (2.64 eV), a reduced charge transfer resistance (49.27 Ω), and a higher average exciton lifetime (48.80 ps). On the other hand, the (Mo 0.300 Ti 0.940 O 1.970 ) 0.925 (RGO) 0.075 NCs with higher Mo(VI) doping show a decrease in the most important photovoltaic parameters, including short-circuit current density (Jsc), open-circuit voltage (Voc), fill factor (FF), and power conversion efficiency (η). The (Mo 0.300 Ti 0.940 O 1.970 ) 0.925 (RGO) 0.075 NCs showed a Jsc of 17,841 mA / cm 2 , a Voc of 690 mV, an FF of 48.70 % and an efficiency of 5.99 %, all of which were lower than those of the optimized (Mo 0.100 Ti 0.980 O 1.990 ) 0.925 (RGO) 0.075NCs. This performance decline is due to the excessive Mo(VI) doping, which acts as a charge trap and promotes charge recombination. In addition, the energy band gap of the (Mo 0.300 Ti 0.940 O 1.970 ) 0.925 (RGO) 0.075 NCs (2.57 eV) do not exhibit optimal charge separation, which limits their ability to conduct charge toward the FTO substrate, further reducing the power conversion efficiency of DSSCs based on these nanocomposites.

[0052] To evaluate photocurrent generation, measurements of the incident photon-to-current conversion efficiency (IPCE) were performed before and after Mo(VI) doping in TiO2 / RGO NCs sensitized with the N719 dye. These measurements provided insights into the photocurrent generation efficiency in a wavelength range from 300 to 800 nm. The samples exhibit photocurrent generation in two distinct wavelength ranges, 300 to 400 nm and 450 to 650 nm, corresponding to the characteristic absorptions of the nanocomposites with a small contribution from the N719 dye and the absorption of the N719 dye alone, respectively. The addition of Mo(VI) doping into the TiO2 host lattice of the TiO2 / RGO nanocomposites leads to a significant enhancement of the IPCE response, reaching 67.88% in the wavelength range from 450 to 650 nm. In contrast, the TiO2 / RGO nanocomposites without Mo(VI) doping show an IPCE response of 58%.46% in the same wavelength range. This indicates that Mo(VI) doping increases the absorption strength of the composite DSSCs, resulting in an improvement of approximately 10% in both wavelength ranges. The results indicate that the Mo(VI)-doped nanocomposites effectively capture a wider range of photon flux from the solar spectrum, covering both the UV and visible regions, while ensuring proper charge carrier separation for efficient light-to-electrical energy conversion.

[0053] The functional groups present in the extracted natural pigments and their effectiveness as sensitizers in dye-sensitized solar cells (DSSCs) were investigated using FTIR and UV-visible absorption spectroscopy. The UV-visible absorption spectra of the natural pigments—betalain, anthocyanin, curcumin, and lawsone—exhibit distinct absorption characteristics corresponding to specific functional groups. Lawsone, extracted from the leaves of Lawsonia inermis, exhibits a broad absorption between 400 and 550 nm, due to π- to π* transitions of the aromatic systems, and a peak between 650 and 680 nm due to the axial ligands of lawsone. Curcumin, extracted from turmeric rhizomes, exhibits a broad absorption from 300 to 500 nm, with a maximum absorption at 400 nm, associated with its phenolic -OH groups.Curcumin occurs in two forms: the enol form exhibits absorption in the visible range due to its planar geometry, which allows for conjugation between π electrons. Anthocyanin extracted from black grapes exhibits absorption in the UV range (250 to 350 nm) and strong absorption in the visible range between 450 and 600 nm, centered at 520 nm, corresponding to the transitions of its phenolic compounds. Betalain extracted from Beta vulgaris exhibits two broad absorption peaks in the visible range, with maxima at 480 and 550 nm, associated with π-to-π* transitions.

[0054] Among these pigments, betalain exhibits the strongest absorption in the visible range, comparable to the commercially preferred dye N719. This makes betalain a promising candidate for the efficient conversion of light into electricity in DSSCs, as it covers a large part of the solar spectrum. Its carboxyl functional groups also enable strong binding to the thin NC films, thus promoting effective charge separation. To evaluate the adsorption properties of the natural pigments on the surface of the thin NC films, the photoelectrodes were immersed in dye solutions for 18 hours in the dark. After rinsing the photoelectrodes to remove excess dye, the desorbed dye solution was analyzed by UV-VIS spectroscopy.This process helped to understand how well the natural pigments adsorb on the surface of the photoelectrodes, which is crucial for converting sunlight into electrical energy in DSSCs.

[0055] The UV-visible absorption spectra of natural pigments such as lawsone, curcumin, anthocyanin and betalain extracted from different sources were measured after desorption from a sensitized (Mo 0.100 Ti 0.980 O 1.990) 0.925 (RGO) 0.075NCs were analyzed for their photoelectrode. Betalain was observed to exhibit maximum coverage of the solar spectrum in the UV-visible range, with particularly strong absorption in the visible range. This suggests that betalain-sensitized photoelectrodes could absorb a higher photon flux for energy conversion in photovoltaic devices. While curcumin exhibited higher absorption strength than other natural pigments, its spectrum coverage was limited, making it less efficient than betalain and anthocyanin at absorbing light. Overall, betalain-sensitized photoelectrodes proved to be the most efficient at converting light into electricity.

[0056] The photovoltaic properties of bare TiO2 and optimized (Mo 0.100 Ti 0.980 O 1.990 ) 0.925 (RGO) 0.075NCs-based photoelectrodes sensitized with various natural pigments were investigated. After sensitization, the photoelectrodes were placed between a counter electrode and the redox liquid mediator electrolyte. The photocurrent density-voltage characteristics of these DSSCs showed that the betalain-sensitized TiO2 photoelectrode exhibited the highest short-circuit current (Jsc) of 2.88 mA / cm 2 , thus outperforming the DSSCs sensitized with lawsone, curcumin, and anthocyanin, which exhibited lower Jsc values. The superior performance of betalain was attributed to its broad optical absorption in the visible range and the carboxyl and hydroxyl functional groups, which enabled a strong connection between the pigment and the photoelectrode surface. When betalain was used to sensitize the optimized (Mo 0.100 Ti 0.980 O 1.990) 0.925 (RGO) 0.075NCs-based DSSCs were used, the Jsc also increased significantly from 2.88 mA / cm 2 to 8.26 mA / cm 2 , indicating a significant improvement in photovoltaic performance. Similar improvements were observed in DSSCs sensitized with anthocyanin, curcumin, and lawsone when using the optimized NCs.

[0057] The results show that TiO2-based dye-sensitized solar cells (DSSCs) sensitized with curcumin exhibit the highest open circuit voltage (Voc) of 480 mV, compared to the cells sensitized with lawsone, anthocyanin, and betalain, which exhibit Voc values ​​of 360 mV, 400 mV, and 420 mV, respectively. However, when curcumin is used as a sensitizer with ternary (Mo 0.100 Ti 0.980 O 1.990) 0.925 (RGO) 0.075When used with TiO2 nanocomposites, no significant improvement in the Voc value is observed after modifying the TiO2 host lattice. In contrast, betalain shows a remarkable improvement in the Voc value when sensitized with the optimized ternary nanocomposite. Furthermore, the Voc value of almost all natural dyes, except curcumin, increases when sensitized with the optimized nanocomposite. Among the natural sensitizers, curcumin in conjunction with TiO2 and the optimized ternary nanocomposite exhibits the highest fill factor (FF) values, with 58.49% for TiO2 and 59.99% for the modified nanocomposite, thus outperforming the other natural dyes in terms of FF. Furthermore, almost all natural sensitizers show higher FF values ​​when used with the optoelectronically modified ternary nanocomposite.

[0058] In terms of photovoltaic conversion efficiency, TiO2-based betalain-sensitized DSSCs exhibit the highest efficiency of 0.64%, which is 83% higher than lawsone (0.11%), 58% higher than curcumin (0.11%), and 39% higher than anthocyanin (0.39%). The higher efficiency of betalain-sensitized DSSCs is attributed to their ability to absorb a larger portion of the solar spectrum and their strong chemical bond with the photoelectrodes, which enhances charge transport and overall power conversion. When these natural pigments are sensitized with the optoelectronically modified ternary nanocomposite, the power conversion efficiency improves significantly: betalain achieves an efficiency of 2.23%, which is 73% higher than that observed for betalain-sensitized DSSCs using bare TiO2.

[0059] Among the different photoelectrodes, IV and IPCE measurements of (Mo 0.100Ti 0.980 O 1.990) 0.925 (RGO) 0.075 NCs sensitized with N719 achieved the highest power conversion efficiency of 7.58%, which is higher than that of TiO 2 / RGO-based photoelectrodes (η= 5.81%). With the optimized photoelectrode composition containing N719, DSSCs based on the natural pigment betalain showed the highest efficiency of 2.23%, compared to efficiencies of 0.38%, 1.29%, and 1.13% for DSSCs sensitized with lawsone, curcumin, and anthocyanin, respectively.

[0060] The drawings and the foregoing description provide examples of embodiments. Those skilled in the art will recognize that one or more of the described elements may well be combined into a single functional element. Alternatively, certain elements may be separated into multiple functional elements. Elements from one embodiment may be added to another embodiment. For example, orders of the processes described herein may be changed and are not limited to the manner described herein. Furthermore, the actions of any flowchart need not be implemented in the order shown; nor do all actions necessarily need to be performed. Also, those actions that are not dependent on other actions may be performed in parallel with the other actions. The scope of the embodiments is in no way limited by these specific examples.Numerous variations, whether explicitly stated in the specification or not, such as differences in structure, dimensions, and material use, are possible. The scope of the embodiments is at least as broad as indicated in the following claims.

[0061] Advantages, other benefits, and solutions to problems have been described above with reference to specific embodiments. However, the advantages, benefits, solutions to problems, and any components that may cause an advantage or solution to occur or become more apparent are not to be construed as a critical, required, or essential feature or component of any or all of the claims. REFERENCES 100 A block diagram of a system for manufacturing dye-sensitized solar cells (DSSCs). 102 Nanocomposite processing unit 102a Mechanism of Sol-Gel Synthesis 102b Dopant insertion mechanism 102c RGO integration mechanism 104 Substrate deposition unit 104a Binder-free doctor blade device 104b Temperature-controlled substrate holding platform 104c Precision spreading mechanism 106 Awareness Unit 108 Electrode assembly unit 110 Photovoltaic power meter

Claims

[1] A system for producing dye-sensitized solar cells (DSSCs) consisting of: a) a nanocomposite manufacturing unit configured to synthesize (MoxTi1-2xO2-δ)1-y(RGO)y nanocomposites, where x is in the range of 0.5 to 3.0 mol% and y is 0.75 wt%; b) a substrate deposition unit configured to deposit the nanocomposites on an FTO substrate using a binderless doctor blade mechanism; (c) a sensitization unit configured to apply sensitizers from the group of natural pigments, including betalain, anthocyanin, curcumin and lawsone; d) an electrode assembly unit for constructing a sandwich DSSC structure; and (e) a photovoltaic power measurement unit for performing IV and IPCE measurements under solar irradiation. [2] The system of claim 1, wherein the nanocomposite manufacturing unit comprises: a) a sol-gel synthesis mechanism for the in situ chemical production of (Mo x Ti 1-2x O 2-δ ) 1-y (RGO) y -nanocomposites, where TiO2 is modified with different compositions of Mo(VI) as a dopant and then additionally doped TiO2 nanoparticles are incorporated on the surface of RGO to improve the optoelectric properties of the composite material; b) a dopant insertion mechanism for incorporating Mo(VI) ions into the TiO2 host lattice; and c) an RGO integration mechanism for surface incorporation of RGO. [3] The system of claim 1, wherein the substrate deposition unit comprises: a) a binder-free doctor blade mechanism for uniform deposition of nanocomposites; b) a temperature-controlled substrate holding platform; and c) a precision distribution mechanism to produce a uniform film thickness. [4] The system of claim 1, wherein the sensitization unit is configured to sensitize the nanoparticle-coated FTO substrate through controlled adsorption mechanisms, wherein the natural pigments are extracted from botanical sources and processed and purified prior to application. [5] The system of claim 1, wherein the fabricated nanoparticles deposited on the FTO substrate are also sensitized with N719 dyes as a model protocol to perform a performance comparison with natural pigments. [6] The system according to claim 1, wherein the electrode assembly unit is configured to include the sensitized photoelectrodes with the counter electrode for manufacturing DSSCs. [7] The system of claim 1, wherein the prepared DSSC device structure consists of a sensitized TiO2 layer sandwiched between a platinum-coated counter electrode and a reduced graphene oxide (RGO) / TiO2-coated FTO glass substrate, using an electrolyte containing I3 between the electrodes. - / 3I - to facilitate cargo transport. [8] The system of claim 1, wherein the photovoltaic power measuring unit is configured to: measure a solar irradiance of 100 mW / cm 2 provides; performs IV characteristic measurements; performs incident photon-to-current efficiency (IPCE) measurements; and compares the power conversion efficiency of different nanocomposite and sensitizer configurations.

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