Next Article in Journal
Nuclear Magnetic Resonance (NMR) Quantifies Stress-Dependent Permeability in Shale: Heterogeneous Compressibility of Seepage and Adsorption Pores
Previous Article in Journal
Biochar as a Catalyst in Persulfate Activation: A Sustainable Approach to Remove Pesticides from Water
Previous Article in Special Issue
Optimizing Light Management in Bifacial Perovskite Solar Cells Using Silica-Based Anti-Dust and Anti-Reflection Coatings for Harsh Environments
 
 
Search for Articles:
Title / Keyword
Author / Affiliation / Email
Journal
Article Type
 
 
Advanced Search
 
Section
Special Issue
Volume
Issue
Number
Page
 
Journals
Processes
Volume 13
Issue 6
10.3390/pr13061857
processes-logo
Submit to this Journal Review for this Journal Propose a Special Issue
► Article Menu

Article Menu

share Share announcement Help format_quote Cite question_answer Discuss in SciProfiles
first_page
settings
Order Article Reprints
Font Type:
Arial Georgia Verdana
Font Size:
Aa Aa Aa
Line Spacing:
Column Width:
Background:
Article

From Structure to Efficiency: Unveiling the Role of Calcination Temperature in Nb2O5-Based DSSCs

by
Ronald Luiz Castiglioni Davi
1,
Edson Araujo de Almeida
2,
Ana Paula Peron
3,
Everson do Prado Banczek
4,
Osvaldo Valarini Junior
5 and
Gideã Taques Tractz
6,*
1
Chemical Engineering Course, Federal Technological University of Paraná-UTFPR-CM, Campo Mourão 87301-899, Paraná, Brazil
2
Graduate Program in Chemistry, State University of Maringá-UEM, Maringá 87020-900, Paraná, Brazil
3
Department of Biodiversity and Nature Conservation, Federal Technological University of Paraná-UTFPR-CM, Campo Mourão 87301-899, Paraná, Brazil
4
Chemistry Department, Central Western State University, Guarapuava 3629-8100, Paraná, Brazil
5
Department of Food and Chemical Engineering, Federal Technological University of Paraná-UTFPR-CM, Campo Mourão 87301-899, Paraná, Brazil
6
Department of Chemistry, Federal Technological University of Paraná-UTFPR-CM, Campo Mourão 85884-000, Paraná, Brazil
*
Author to whom correspondence should be addressed.
Processes 2025, 13(6), 1857; https://doi.org/10.3390/pr13061857
Submission received: 21 May 2025 / Revised: 9 June 2025 / Accepted: 10 June 2025 / Published: 12 June 2025
(This article belongs to the Special Issue Innovations in Solar Cell Technology: Materials, Efficiency and Sustainability)
Browse Figures
Versions Notes

Abstract

:
The development of dye-sensitized solar cells (DSSCs) has gained prominence as an economical alternative for photovoltaic energy conversion. This work investigates the synthesis of niobium pentoxide (Nb2O5) by the Pechini method, followed by calcination at different temperatures (500 °C, 600 °C and 700 °C) to evaluate its structural, morphological, and electrochemical properties as a photoanode material in DSSCs. SEM and XRD analyses revealed that calcination at 600 °C produced a material with optimized particle size (642.17 ± 37 nm) and adequate crystalline structure, favoring dye adsorption and electronic transport. Electrochemical characterization, including open-circuit potential and impedance spectroscopy, indicated that the sample at 600 °C presented superior photovoltaic performance, achieving a power conversion efficiency of 1.39% and electron lifetime equal to 0.159 s. These findings suggest that Nb2O5, under controlled calcination conditions, may act as a promising alternative to TiO2 substitution in DSSC applications.

1. Introduction

The intensification of pollution, depletion of natural resources, and the acceleration of the greenhouse effect have significantly aggravated environmental concerns in recent years. In this context, photovoltaic systems have emerged as a promising alternative for sustainable energy generation, drawing increasing attention to renewable and low-emission energy sources. Among various photovoltaic technologies, dye-sensitized solar cells (DSSCs) stand out due to their low production cost, simple fabrication process, and potential application in flexible devices, making them an attractive option for clean energy conversion [1,2].
DSSCs use a dye to absorb light and generate electrons, which are transferred to a semiconductor, usually titanium oxide (TiO2), where charge separation occurs [3]. Despite its low cost and chemical stability, TiO2 has limitations such as a wide band gap (~3.2 eV), which restricts absorption to ultraviolet light, and low electrical conductivity, which requires structural modifications or doping to improve its performance. Similarly, the use of new materials such as niobium pentoxide (Nb2O5) [4], zinc oxide (ZnO) [5], and cerium oxide (CeO2) [6], among others, is promising, as they present limitations and customized properties that can be easily modified by synthetic routes.
Because of its structural and electrical characteristics, Nb2O5 has sparked interest in materials research for solar devices [7]. Niobium (Nb) in oxide form can play a role as a dopant when added to semiconductor oxides like TiO2, encouraging the creation of intermediate electronic states in the forbidden band gap and favoring visible light absorption [8]. Doping the material can enhance its electrical conductivity, reducing charge transfer resistance and minimizing electronic recombination. Similarly, Nb2O5 has advantages over TiO2, not only related to the production cost, but also in morphology and electronic properties [8].
Beyond their role in DSSCs, metal oxides are also extensively utilized in perovskite-based solar cells and related optoelectronic devices [9,10,11]. Perovskite materials often incorporate oxide layers that serve as charge transport or blocking layers, benefiting from the stability and tunable properties of metal oxides. These oxides, such as TiO2 and Nb2O5, have been widely studied for their ability to improve device performance by enhancing charge extraction and reducing recombination losses [9,12]. While perovskites themselves show outstanding light absorption and charge carrier properties, challenges related to stability and toxicity persist [13,14]. Thus, metal oxides continue to be essential components in the quest for more efficient and durable photovoltaic technologies, offering robustness and adaptability through various synthesis methods.
There are various ways to synthesize these charge transport materials, but one of the most popular methods for producing metal oxides with excellent purity and morphological control is the Pechini pathway [15]. This process creates a polymeric precursor in which a carboxylic acid, like citric acid, chelates the metal ions, and then a polyol alcohol, like ethylene glycol, polymerizes them. The polymeric precursor is transformed into metal oxides with certain structural properties for photovoltaic applications during calcination. This temperature could influence the crystal morphology, structure, and tailor the performance of the material when applied in several areas [15].
The objective of this work is to synthesize Nb2O5 using the Pechini methodology, with calcination at different temperatures, analyzing the material structurally and morphologically, with subsequent application in a photovoltaic device.

2. Materials and Methods

Nb2O5 particles were prepared by Pechini methodology as follows: an amount of 79.2 g of citric acid was dissolved in 300 mL of ethylene glycol, under stirring at 70 °C until complete solubilization. Then, 6.22 g of ammonium niobium complex, provided by CBMM (Companhia Brasileira de Metalurgia e Mineração, Araxá, Minas Gerais, Brazil), was inserted, and the temperature was increased to 100 °C [4]. The resin formed was calcinated for 4 h, at temperatures of 500 °C, 600 °C, and 700 °C with a puff deagglomeration at 400 °C. The production of Nb2O5 is illustrated in the flowchart in Figure S1 in Supplementary Information.
The synthesized powders were evaluated by XRD diffraction, using D2 phaser Bruker equipment (using CuKα radiation source with a wavelength of 0.1506 nm operated at 30 kV and 10 mA), and by light dynamic scattering using Litesizer 500 and Anton PAAR equipment, coupled with a Zeta potential analyzer (in deionized water solution). Scanning Electron Microscopy, using Tescan Vega Microscopy, was also performed, with magnification of 500× for morphological characterization. The energy band gap of oxides was calculated using UV-Vis spectra of samples, obtained in UV-VIS-NIR, Plus Shimadzu, using the Kubelka–Munk method, described in Equation (S1) of the Supplementary File [6].
Nb2O5 paste was prepared as follows: an amount of 3 g of Nb2O5 was mixed with 0.1 mL of acetyl acetone, 0.1 mL of Triton-X, 0.1 mL of polyethylene glycol, and 3 mL of deionized water, under maceration for 30 min [16,17,18]. The paste was coated under a fluorine-doped tin oxide surface (FTO; 7 Ω sq−1 Aldrich®) by the doctor blading method. Films were sintered for 30 min at 450 °C and impregnated with N719 dye solution in ethanol (1 × 10−4 mol L−1) for 24 h.
Solar cells with an active area of 0.2 cm2 were assembled in sandwich format, using the anode (Nb2O5 + dye) with a counter electrode produced using platinum (Pt) [18]. The charge remediation was made by iodine electrolytes [18]. The techniques employed to electrochemically characterize DSSC were the open-circuit curves, j-V curves, and Electrochemical Impedance Spectroscopy (EIS) (0.01–1 kHz with 10 mV of amplitude). These techniques were employed in a Zhenium Zahner potentiostat, coupled with the Xe lamp at 100 mW cm−2 under 1.5 AM irradiation.

3. Results and Discussion

3.1. Morphological and Structural Characterization

In Figure 1, the SEM micrographs for Nb2O5 particles produced are depicted.
Micrographs obtained by Scanning Electron Microscopy (SEM) of Nb2O5 synthesized by Pechini methodology at different temperatures show specific morphological characteristics that can be correlated with the synthesis conditions. In general, the samples presented an irregular morphology, with a marked presence of agglomerates, which is in accordance with the literature for the Pechini methodology [19].
Irregular morphology is particularly interesting for applications in emergent photovoltaic systems, since the rough surfaces and high surface area enhance the dye-sensitized adsorption [20,21]. In addition, these results may also be exploited in other areas, as pollutant adsorption, providing a greater capacity for interaction with the target species.
The analysis of the particle size distribution (Figures S2–S4 in Supplementary Information) indicated a predominance in the range of 20–40 µm, with better homogeneity observed in the samples treated at 500 °C and 600 °C. On the other hand, the sample calcined at 700 °C exhibited a higher concentration of particles around the 20 µm size range. This can be attributed to an enhanced sintering process at this temperature, promoting particle coalescence and growth, resulting in larger and denser agglomerates. This behavior is consistent with the observed increase in average particle size, reflecting the thermal-driven grain growth and particle fusion at higher calcination temperatures. To analyze the particles in suspension, Dynamic Light Scattering was performed, with Zeta potential analysis, as depicted in Table 1.
The analysis of particle size and zeta potential values corroborates these observations. It can be observed that the sample treated at 500 °C presented an average diameter of 827.63 ± 26 nm and a zeta potential of −25.53 ± 2.84 mV, indicating the formation of intermediate-sized particles with good colloidal stability due to the high negative value of zeta potential. The sample at 600 °C presented a reduced diameter of 642.17 ± 37 nm and a lower superficial charge, when compared to the others, suggesting a decrease in colloidal stability with a higher propensity to agglomerate formation [22]. Since the organic residues were rapidly burned without a heating ramp, between 500 °C and 600 °C, it is indicated that the powder initially undergoes fragmentation due to the release of gases such as H2O and CO2 (reducing the apparent particle size), followed by particle rearrangement as they begin to fuse and sinter, thus not following the expected trend of increasing particle size with temperature.
The sample calcinated at 700 °C showed a significant increase in particle size, reaching 1022.57 ± 46.8 nm, which can be attributed to more intense sintering at high temperatures, resulting in larger particles and denser agglomerates. It is important to emphasize that larger particles tend to reduce the active surface area available for the adsorption of dyes, decreasing the efficiency in solar energy conversion [23]. On the other hand, rough surfaces and heterogeneous particle distribution can still enhance the adsorption, as seen in those treated at lower temperatures.
X-ray diffraction of the Nb2O5 samples synthesized via the Pechini method and calcinated at several temperatures is presented in Figure 2.
The diffraction patterns show restricted and well-defined peaks in the same 2θ regions, indicating the formation of crystalline materials. The absence of significant deviation or emergence of new peaks suggests that there was no phase transition between the observed temperatures. The identification of the crystalline planes was performed using Crystallographica® software (Version 3.1), allowing the cataloging of the peaks and the determination of (001), (180), and (181) planes, characteristic of the orthorhombic phase of Nb2O5 [4,7]. These findings reinforce the stability of the crystalline structure under the conditions tested, and are relevant for the application of materials such as photoanodes in solar systems. To evaluate the average crystal size, the Scherrer equation (Equation (1)) was applied, considering the most intense peak in each sample [7].
D = (Kλ)/B(Cos θ)
With D representing the crystallite size, K is the Scherrer constant (K = 0.9), λ the wavelength of X-rays, B the FWHM of the diffraction peak, and θ the Bragg angle. Using Equation (1), the values of 12.26 nm, 14.39 nm, and 18.51 nm were obtained for powders sintered at 500 °C, 600 °C, and 700 °C, respectively. In essence, a progressive increase in crystallite size is observed with increasing temperature, which is associated with the growth of the crystalline domains. These values are in agreement with those reported by Eblagon et al. [24] for Nb2O5 synthesis and present a particularly interesting behavior for DSSC use, since adequate control of crystalline size can also influence the surface area available for dye adsorption, impacting the photoconversion energy efficiency of the device.

3.2. Electrochemical Device Characterization

Open-circuit potential (Voc) tests were performed under conditions with and without illumination, in order to evaluate the photosensitivity of the DSSC device constructed with Nb2O5 as the electron transport material (Figure 3).
In the absence of light, the potential recorded was close to 0 V, confirming the absence of photosensitive activity. With the application of light, Voc increased significantly, reaching a value of approximately 0.7 V [25]. This value is considered promising when compared to TiO2, which generally presents open-circuit potentials in the same range (~0.7 V), demonstrating the viability of Nb2O5 as a potential replacement for DSSCs [25].
The formation of the open-circuit potential is closely related to the difference between the Fermi level of the semiconductor and the redox potential of the electrolyte used [26]. The results obtained indicate that the conduction band of Nb2O5 is adequately positioned for the injection of electrons from the dye to the semiconductor, favoring the charge separation process. Furthermore, the Voc values recorded for the powders calcined at different temperatures did not show significant variations, suggesting that the conduction band position remained stable regardless of the increase in crystallite size or material crystallinity, according to a gap value of 2.92 eV (Figure S5 in Supplementary Information), obtained with no variation for all samples [4]. The direct band gap was calculated, according to the approach for Nb2O5 reported by several studies in the literature, highlighting the relevance of this type of transition in various experimental and structural contexts [27,28,29]. This stability is a positive factor for future applications of Nb2O5 in dye-sensitized solar cells and other emergent photovoltaic applications. On the other hand, the current produced in the device is significantly influenced by particle properties, such as microstructure, electron diffusion length, charge recombination, porosity, and dye loading. Therefore, j-V curves were created for solar cells and are depicted in Figure 4.
As can be seen in Figure 4, the cell produced at 600 °C presented the highest current density, resulting in a larger area under the curve, which is directly reflected in a higher photovoltaic efficiency (PCE). Using Equation (2), PCE could be calculated, with maximum values of current density (Jsc), potential (Voc), and Fill Factor (FF), providing a more accurate indication of the energy conversion capacity of the photovoltaic device [30].
PCE = (Jsc × Voc × FF/Pin)
Analyzing the results in Table 2, the cell produced with Nb2O5 at 600 °C showed better PCE, equal to 1.39%. This performance is mainly associated with the higher current density obtained, which can be related to the smaller particle size observed to this sample, resulting in an increase in the specific surface area and, consequently, in a greater number of sites available for dye adsorption [31,32]. On the other hand, the sample calcined at 700 °C, despite presenting the highest Fill Factor (0.536), presented the lowest efficiency (0.55%), possibly due to the larger crystallite size (18.51 nm) and the consequent reduction in the surface area available for dye adsorption. The sample calcined at 500 °C presented an intermediate behavior, with an efficiency of 1.13%. The short-circuit current density (Jsc) values presented in Table 2 reveal a clear dependence on the calcination temperature. An increase from 3.19 mA cm−2 at 500 °C to 4.23 mA cm−2 at 600 °C indicates enhanced charge transport and reduced recombination, likely due to the improved crystallinity and interconnectivity of the TiO2 particles. However, a subsequent decrease to 1.36 mA cm−2 at 700 °C suggests that excessive grain growth may hinder dye adsorption and reduce the effective surface area, ultimately reducing photocurrent generation.
These results are promising, considering that oxide substitutes for TiO2 rarely achieve higher efficiencies. For instance, SnO2 in nanoparticulate form typically exhibits efficiencies in energy conversion around 0.9% [33], while ZnO reaches approximately 0.57% [34]. Nb2O5 when combined with other oxides can enhance the system efficiency, reaching values in the range of 1–2%, and is also highly effective in the fabrication of counter electrodes [35,36]. Similarly, the oxides developed and studied here may act as enhancers for the underlying layers of other materials, creating a synergistic effect. It is also noteworthy that the systems developed in this study do not include an electron-blocking layer using TiCl4 or an efficient sealing mechanism, which could further boost the obtained values. To gain a deeper understanding of the mechanisms involved in charge transfer and recombination processes within the solar cell, it is essential to examine not only the overall performance through j-V curves but also the dynamics of the internal interfaces of the device [37]. In this context, Electrochemical Impedance Spectroscopy (EIS) was applied, as shown in Figure 5.
The analysis of the EIS curves performed on the dye-sensitized Nb2O5 system, as shown in Figure 5, reveals crucial information about the charge transfer and recombination processes that occur at the solar cell interfaces [38]. The Nyquist diagram shown in Figure 5 highlights the presence of a capacitive arc at high frequencies, related to the behavior of the counter electrode, which responds to short relaxation times [17]. This behavior is typical of dye-sensitized systems, in which charge transfer occurs rapidly at the device interfaces.
In addition, a distinct capacitive behavior is observed at high frequencies, with the variation associated with the calcination temperature of the Nb2O5. This phenomenon corroborates the hypothesis that the calcination process directly influences the charge transfer processes that occur at the working electrode interface [39]. The change in the capacitive arc as the calcination temperature increases is a clear indication that the material microstructure and surface characteristics are being modified, altering the charge transfer behavior in the system.
Specifically, for the systems produced at calcination temperatures of 600 °C, high conductivity and facility in redox reactions were observed, compared to the other systems. These results are consistent with the electrochemical data obtained for the cell current, which indicate greater efficiency in redox reactions and a significant reduction in the system resistance [40]. This improvement in charge transport properties can be attributed to the formation of a structure more favorable to electrical conduction, possibly due to greater surface activation and better crystalline organization of the Nb2O5 calcined at 600 °C [23]. In addition, with the fitted Nyquist diagram and the equivalent circuit used, Table 3 and Figures S6–S8 in Supplementary Information provide information on the solar cell resistance interfaces.
On the other hand, the oxide produced at 500 °C presented intermediate resistances of charge transportation (RCT = 305.0 Ω), evidencing less efficient performance compared to the system calcined at 600 °C (RCT = 66.4 Ω). This suggests that the calcination temperature of 500 °C does not favor the formation of ideal microstructural features for charge transfer, resulting in less efficient electrochemical behavior. Similarly, the system calcined at 700 °C showed high resistances (RCT = 736.0 Ω), which indicates a reduction in the efficiency of charge transfer, possibly due to the higher crystallite size, which may affect the formation of defects in the structure that hinder redox reactions [23].
Using Equation (3), it is possible to calculate τe, the electron lifetime (with f representing the frequency of the middle semicircle) [4,41].
τe = 1/2пf
The τe results indicate that the electronic lifetime increases with increasing calcination temperature. For the system calcined at 500 °C, the electronic lifetime is 0.031 s, which reflects a rapid recombination of the charge carriers [42,43,44]. In contrast, the system calcined at 600 °C presents an electronic lifetime of 0.159 s, indicating a slower recombination and, therefore, a higher charge transfer efficiency. The system calcined at 700 °C, with τe of 0.265 s, suggests an even slower recombination, but as observed in the impedance curves, this improvement is not accompanied by an increase in the overall efficiency of the system, due to the increase in resistances associated with this calcination process [40,45]. Although an increase in electron lifetime (τe) was observed with higher calcination temperatures, this parameter alone does not ensure improved device efficiency. The overall performance also depends on how effectively the photogenerated electrons are collected, which is governed by the electron collection time. In cases where the material becomes more compact or loses surface area, as observed in particles produced at 700 °C, electron transport may be hindered, reducing collection efficiency despite the longer τe. A proper evaluation of charge collection dynamics requires techniques such as Intensity-Modulated Photocurrent Spectroscopy (IMPS), which were not employed in the present study [18].
These data confirm that the calcination temperature is a critical parameter in modulating the electrochemical properties of the dye-sensitized Nb2O5 system. Impedance and electronic lifetime analysis provide a detailed understanding of charge transport mechanisms and the effects of calcination temperature on solar cell interfaces.

4. Conclusions

The synthesis of Nb2O5 by the Pechini method proved to be an effective way to obtain particles with adjustable morphology and structural characteristics by controlling the calcination temperature. The results obtained indicate that increasing the temperature promotes the growth of crystalline domains and the formation of large agglomerates, as observed by SEM images and XRD measurements. On the other hand, calcination at 600 °C showed an intermediate behavior, with particles of reduced size (642.17 ± 37nm) and a relatively homogeneous surface.
Electrochemical measurement of the dye-sensitized solar cells revealed that the material calcinated at 600 °C produced a higher photoconversion energy efficiency (PCE = 1.39%). Electrochemical impedance spectroscopy reinforced the conclusion, with particles produced at intermediate temperatures having reduced charge transfer resistance and an electron lifetime of 0.159 s, which is supposed to be related to the morphology, electrical conductivity, and surface area for dye adsorption.
To enhance the overall efficiency of the DSSC, future work could focus on improving dye adsorption through surface functionalization of the Nb2O5 particles, engineering the photoanode architecture to increase surface area and light scattering, and incorporating co-sensitizers or conductive additives to facilitate charge transport and reduce recombination losses.

Supplementary Materials

The following supporting information can be downloaded at: https://www.mdpi.com/article/10.3390/pr13061857/s1. Figure S1: Flowchart diagram of Nb2O5 process production by Pechini methodology; Figure S2: Particle distribution to Nb2O5 calcinated at 500 °C; Figure S3: Particle distribution to Nb2O5 calcinated at 600 °C; Figure S4: Particle distribution to Nb2O5 calcinated at 700 °C; Figure S5: Gap estimated by Kubelka–Munk method to Nb2O5 studied. Figure S6: Equivalent circuit used to fit EIS Nyquist diagram to dye-sensitized solar cells in A, with fitted diagram in B to Nb2O5 produced at 500 °C; Figure S7: Equivalent circuit used to fit EIS Nyquist diagram to dye-sensitized solar cells in A, with fitted diagram in B to Nb2O5 produced at 600 °C.; Figure S8: Equivalent circuit used to fit EIS Nyquist diagram to dye-sensitized solar cells in A, with fitted diagram in B to Nb2O5 produced at 700 °C.

Author Contributions

R.L.C.D.: conceptualization, methodology, formal analysis, resources, writing—review and editing, supervision; E.A.d.A.: conceptualization, methodology, formal analysis, writing—original draft preparation, visualization; A.P.P.: formal analysis, investigation, data curation, project administration; E.d.P.B.: validation, data curation, writing—original draft preparation; O.V.J.: investigation, supervision, project administration; G.T.T.: conceptualization, methodology, formal analysis, validation, investigation, project administration, writing—original draft preparation, funding acquisition. All authors have read and agreed to the published version of the manuscript.

Funding

This research received no external funding.

Data Availability Statement

The original contributions presented in this study are included in the article/supplementary material. Further inquiries can be directed to the corresponding author.

Acknowledgments

The authors are grateful to UNICENTRO and UEM for all the electrochemical and organic analyses. The authors would like to thank the Multiuser Laboratory of Federal University of Technology—Paraná—Campus Campo Mourão—for the performed analyses. The authors also thank the “Laboratório Multiusuário da UTFPR Campus Londrina (LabMulti-LD)” for the analyses.

Conflicts of Interest

The authors declare no conflicts of interest.

Abbreviations

The following abbreviations are used in this manuscript:
PCEPhotoconversion Energy Efficiency
jscShort-Circuit Current
VocOpen-Circuit Potential
FFFill Factor
DSSCDye-Sensitized Solar Cell
FTOFluorine-Doped Tin Oxide
PinIncident Power
AMAir Mass
EISElectrochemical Impedance Spectroscopy

References

  1. Kraidy, A.F.; Yapi, A.S.; Saint-Gregoire, P.; Vaillant-Roca, L.; Eke, S.; Mouangue, R.; Jamali, A.; Gagou, Y. Enhancement of Natural Dye-Sensitized Solar Cell Efficiency Through TiO2 Hombikat UV100 and TiO2 P25 Photoanode Optimization. Processes 2024, 12, 2481. [Google Scholar] [CrossRef]
  2. Wazzan, N. Structural Engineering of π-Linker Aromaticity in Anthanthrene-Based Dyes with D–π–A Configuration: DFT Investigation to Enhance Charge Transfer in DSSCs. Processes 2025, 13, 418. [Google Scholar] [CrossRef]
  3. Tractz, G.T.; Viomar, A.; Dias, B.V.; De Lima, C.A.; Banczek, E.P.; Da Cunha, M.T.; Antunes, S.R.M.; Rodrigues, P.R.P. Recombination study of dye sensitized solar cells with natural extracts. J. Braz. Chem. Soc. 2019, 30, 371–378. [Google Scholar] [CrossRef]
  4. Tractz, T.; Staciaki, F.; Regina, S.; Antunes, M.; Banczek, P.; Taras, M.; Rog, P. Nb2O5 synthesis and characterization by Pechini method to the application as electron transport material in a solar device. Solar Energy 2021, 216, 1–6. [Google Scholar] [CrossRef]
  5. Larsson, L.F.G.; Arielo, G.; Maia, R.G.T.T.; Cristina, D.; Oliszeski, S.; Helleis, R. Application of Zinc Oxide in Hybrid Solar Cells Using a P3HT and P3OT Polymer Junction as Charge Carrier. Mater. Res. 2019, 22, e20180820. [Google Scholar] [CrossRef]
  6. Tractz, T.; Viomar, A.; Dias, B.V.; Rodrigues, P.R.P. Photoelectrochemical Behavior of the Cell FTO/TiO2/CeO2/N719 Obtained from the Pechini and Precipitation of Cerium Oxide Methods. J. Electron. Mater. 2018, 47, 5556–5563. [Google Scholar] [CrossRef]
  7. Lü, X.; Mou, X.; Wu, J.; Zhang, D.; Zhang, L.; Huang, F.; Xu, F.; Huang, S. Improved-Performance Dye-Sensitized solar cells using Nb-Doped TiO2 electrodes: Efficient electron Injection and transfer. Adv. Funct. Mater. 2010, 20, 509–515. [Google Scholar] [CrossRef]
  8. Hossain, M.I.; Aissa, B.; Khandakar, A.; Thomas, K.; Rahman, A.; Mansour, S. Exploring the optical and morphological properties of metal oxide thin films produced via reactive electron beam evaporation. Cogent Eng. 2024, 11, 2338144. [Google Scholar] [CrossRef]
  9. Hossain, M.I.; Alharbi, F.H.; Tabet, N. Copper oxide as inorganic hole transport material for lead halide perovskite based solar cells. Sol. Energy 2015, 120, 370–380. [Google Scholar] [CrossRef]
  10. Haque, M.M.; Mahjabin, S.; Abdullah, H.B.; Akhtaruzzaman, M.; Almohamadi, H.; Islam, M.A.; Hossain, M.I.; Ibrahim, M.A.; Chelvanathan, P. Exploring the theoretical potential of tungsten oxide (WOx) as a universal electron transport layer (ETL) for various perovskite solar cells through interfacial energy band alignment modulation. J. Phys. Chem. Solids 2025, 196, 112324. [Google Scholar] [CrossRef]
  11. Hossain, M.I.; Al Kubaisi, G.; Aïssa, B.; Mansour, S. Probing the hydrophilic behaviour of e-beam evaporated silica thin films for PV-soiling application. Mater. Sci. Technol. 2022, 38, 753–759. [Google Scholar] [CrossRef]
  12. Hossain, M.I.; Chelvanathan, P.; Aissa, B.; Khandakar, A.; Rahman, A.; Mansour, S. Enhanced perovskite solar cells performance with TiOx and SnOx thin films as electron transport layers. Sci. Rep. 2025, 15, 7709. [Google Scholar] [CrossRef] [PubMed]
  13. Hossain, M.I.; Tong, Y.; Shetty, A.; Mansour, S. Probing the degradation pathways in perovskite solar cells. Sol. Energy 2023, 265, 112128. [Google Scholar] [CrossRef]
  14. Hossain, M.I.; Chelvanathan, P.; Khandakar, A.; Thomas, K.; Rahman, A.; Mansour, S. Enhanced efficiency of bifacial perovskite solar cells using computational study. Sci. Rep. 2024, 14, 12984. [Google Scholar] [CrossRef]
  15. Raba-Páez, A.M.; Suarez-Ballesteros, D.N.; Martínez-Zambrano, J.J.; Rojas-Sarmiento, H.A.; Rincón-Joya, M. Pechini method used in the obtention of semiconductor nanoparticles based niobium. Dyna 2015, 82, 52–58. [Google Scholar] [CrossRef]
  16. Guimaraes, R.R.; Parussulo, A.L.A.; Araki, K. Impact of nanoparticles preparation method on the synergic effect in anatase/rutile mixtures. Electrochim. Acta 2016, 222, 1378–1386. [Google Scholar] [CrossRef]
  17. Guimaraes, R.R.; Parussulo, A.L.A.; Toma, H.E.; Araki, K. New tunable ruthenium complex dyes for TiO2 solar cells. Inorganica Chim. Acta 2013, 404, 23–28. [Google Scholar] [CrossRef]
  18. Tractz, G.T.; Antunes, S.R.M.; Rodrigues, P.R.P. Nb/TiO2 oxides: A study of synthesis and electron transport mechanism as an ETL in a solar device. J. Photochem. Photobiol. A Chem. 2023, 444, 114899. [Google Scholar] [CrossRef]
  19. Maia, P.R.P.R.G.A.R.; Larsson, L.F.G.; Viomar, A.; Maia, E.C.R.; de Santana, H. Aperfeiçoamento da produção de partículas de óxido de zinco para aplicação em células solares. Cerâmica 2016, 62, 91–97. [Google Scholar] [CrossRef]
  20. Maia, G.A.R.; Larsson, L.F.G.; Viomar, A.; Matos, L.A.C.; Antunes, S.R.M.; Maia, E.C.R.; Oliveira, M.F.; Cunha, M.T.; Rodrigues, P.R.P. Influence of zinc oxide morphology in hybrid solar cells of poly(3-octylthiophene). J. Mater. Sci. Mater. Electron. 2016, 27, 8271–8278. [Google Scholar] [CrossRef]
  21. Vanlaeke, P.; Swinnen, A.; Haeldermans, I.; Vanhoyland, G.; Aernouts, T.; Cheyns, D.; Deibel, C.; D’Haen, J.; Heremans, P.; Poortmans, J.; et al. P3HT/PCBM bulk heterojunction solar cells: Relation between morphology and electro-optical characteristics. Sol. Energy Mater. Sol. Cells 2006, 90, 2150–2158. [Google Scholar] [CrossRef]
  22. Jarzynska, K.; Ciura, K.; Gao, X.J.; Mikolajczyk, A.; Gao, X.; Puzyn, T. Understanding the zeta potential of nanomaterials through predictive nanoinformatics. Nano Today 2025, 64, 102783. [Google Scholar] [CrossRef]
  23. Hagfeldt, A.; Boschloo, G.; Sun, L.; Kloo, L.; Pettersson, H. Dye-Sensitized Solar Cells. Chem. Rev. 2010, 110, 6595–6663. [Google Scholar] [CrossRef]
  24. Eblagon, K.M.; Malaika, A.; Ptaszynska, K.; Pereira, M.F.R.; Figueiredo, J.L. Impact of thermal treatment of Nb2O5 on its performance in glucose dehydration to 5-hydroxymethylfurfural in water. Nanomaterials 2020, 10, 1685. [Google Scholar] [CrossRef]
  25. O’Regan, B.; Grätzel, M. A low-cost, high-efficiency solar cell based on dye-sensitized colloidal TiO2 films. Nature 1991, 353, 737–740. [Google Scholar] [CrossRef]
  26. Grätzel, M. Photoelectrochemical cells. Nature 2001, 414, 338–344. [Google Scholar] [CrossRef]
  27. Sathasivam, S.; Williamson, B.A.D.; Althabaiti, S.A.; Obaid, A.Y.; Basahel, S.N.; Mokhtar, M.; Scanlon, D.O.; Carmalt, C.J.; Parkin, I.P. Chemical Vapor Deposition Synthesis and Optical Properties of Nb2O5 Thin Films with Hybrid Functional Theoretical Insight into the Band Structure and Band Gaps. ACS Appl. Mater. Interfaces 2017, 9, 18031–18038. [Google Scholar] [CrossRef]
  28. Sultana, R.; Islam, K.; Chakraborty, S. Tuning Optical and Electrochemical Properties of Nb2O5 Thin Films via WO3 Doping. Trans. Electr. Electron. Mater. 2025, 26, 48–59. [Google Scholar] [CrossRef]
  29. Chaiworn, P.; Teerananattapong, W.; Reunchan, P.; Tubtimtae, A.; Wongrat, E. Effect of tungsten oxide concentration on structural, morphological, compositional, dispersion energy, and linear/nonlinear optical properties of niobium pentoxide thin films. Opt. Mater. 2025, 161, 116807. [Google Scholar] [CrossRef]
  30. Longo, C.; De Paoli, M.A. Dye-Sensitized Solar Cells: A Successful Combination of Materials. J. Braz. Chem. Soc. 2003, 14, 889–901. [Google Scholar] [CrossRef]
  31. Wu, J.J.; Chen, G.R.; Yang, H.H.; Ku, C.H.; Lai, J.Y. Effects of dye adsorption on the electron transport properties in ZnO-nanowire dye-sensitized solar cells. Appl. Phys. Lett. 2007, 90, 2007–2009. [Google Scholar] [CrossRef]
  32. Kim, T.Y.; Kim, J.H.; Kim, H.B.; Park, K.H.; Lee, J.W.; Cho, S.Y. Adsorption and kinetics properties of TiO2 photoelecrode using natural paprika oleoresin (Capsicum annuum L.) dye for dye-sensitized solar cells. Int. J. Electrochem. Sci. 2018, 13, 3935–3947. [Google Scholar] [CrossRef]
  33. Ramasamy, E.; Lee, J. Ordered mesoporous SnO2-based photoanodes for high-performance dye-sensitized solar cells. J. Phys. Chem. C 2010, 114, 22032–22037. [Google Scholar] [CrossRef]
  34. Valerio, T.; Arielo, G.; Maia, R.; Fernanda, L. Study of the Nb2O5 Insertion in ZnO to Dye-sensitized Solar Cells 2. Material and Methods. Mater. Res. 2019, 22, 1–5. [Google Scholar] [CrossRef]
  35. Valerio, T.L.; Tractz, G.; Maia, G.A.R.; Banczek, E.D.P.; Rodrigues, P.R.P. Minimizing of charge recombination by Nb2O5 addition in dye-sensitized solar cells. Opt. Mater. 2020, 109, 110310. [Google Scholar] [CrossRef]
  36. de Lima, A.A.; Tractz, G.T.; Macedo, A.G.; Thomazi, F.; Rodrigues, P.R.P.; Dartora, C.A. Electrochemical investigation of PEDOT:PSS and Nb2O5 composites as counter electrodes for dye-sensitized solar cells. Opt. Mater. 2022, 132, 112763. [Google Scholar] [CrossRef]
  37. Yang, J.H.; Bark, C.W.; Kim, K.H.; Choi, H.W. Characteristics of the dye-sensitized solar cells using TiO2 nanotubes treated with TiCl4. Materials 2014, 7, 3522–3532. [Google Scholar] [CrossRef]
  38. Bard, A.J.; Faulkner, L.R. Electrochemical Methods: Fundamentals and Applications, 2nd ed.; Jonh Wiley & Sons, Inc.: New York, NY, USA, 2000. [Google Scholar]
  39. Liberatore, M.; Decker, F.; Burtone, L.; Zardetto, V.; Brown, T.M.; Reale, A.; Di Carlo, A. Using EIS for diagnosis of dye-sensitized solar cells performance. J. Appl. Electrochem. 2009, 39, 2291–2295. [Google Scholar] [CrossRef]
  40. Gratzel, M.; Wang, Q.; Moser, J.E. Electrochemical impedance spectroscopic analysis of dye-sensitized solar cells. J. Phys. Chem. B 2005, 109, 14945–14953. [Google Scholar] [CrossRef]
  41. Tractz, G.T.; Dias, B.V.; Banczek, E.P.; da Cunha, M.T.; Alves, G.J.T.; Rodrigues, P.R.P. Dye Sensitized Solar Cells (CSSC): Perspectives, Materials, Functioning and Characterization Techniques. Rev. Virtual De. Química 2020, 12, 748–774. [Google Scholar] [CrossRef]
  42. Bisquert, J.; Fabregat-santiago, F. Electron Lifetime in Dye-sensitized solar cells: Theory and Interpretation of Measurements. J. Phys. Chem. C 2009, 113, 17278–17290. [Google Scholar] [CrossRef]
  43. Camargo Matheus, A.P.; Gonçalves Larsson, L.F.; Tractz, G.T.; Pinto Rodrigues, P.R. The TiO2/electrolyte interface in DSSCs: An electrochemical study of the insertion of BTAH, BZM, and indole. Opt. Mater. 2025, 159, 116637. [Google Scholar] [CrossRef]
  44. Rigueira, R.F.; Tractz, G.T.; Barancelli, D.A. Fabrication of a dye sensitized solar cell using TiO2 sensitized with a mono-carbonyl curcumin analog. J. Iran. Chem. Soc. 2024, 21, 2095–2101. [Google Scholar] [CrossRef]
  45. Bisquert, J.; Fabregat-Santiago, F. Impedance Spectroscopy: A General Introduction and Application to Dye-Sensitized Solar Cells, 1st ed.; EPFL Press: Lausanne, Switzerland, 2010. [Google Scholar]
Processes 13 01857 g001
Figure 1. SEM micrographs of Nb2O5 particles produced by Pechini methodology at 500 °C (A), 600 °C (B), and 700 °C (C).
Figure 1. SEM micrographs of Nb2O5 particles produced by Pechini methodology at 500 °C (A), 600 °C (B), and 700 °C (C).
Processes 13 01857 g001
Processes 13 01857 g002
Figure 2. XRD patterns of Nb2O5 particles produced by Pechini methodology at 500 °C, 600 °C, and 700 °C.
Figure 2. XRD patterns of Nb2O5 particles produced by Pechini methodology at 500 °C, 600 °C, and 700 °C.
Processes 13 01857 g002
Processes 13 01857 g003
Figure 3. Open-circuit potential curves for DSSC produced with Nb2O5 particles calcinated at 500 °C, 600 °C, and 700 °C.
Figure 3. Open-circuit potential curves for DSSC produced with Nb2O5 particles calcinated at 500 °C, 600 °C, and 700 °C.
Processes 13 01857 g003
Processes 13 01857 g004
Figure 4. j-V curves for DSSC produced with Nb2O5 particles calcinated at 500 °C, 600 °C, and 700 °C.
Figure 4. j-V curves for DSSC produced with Nb2O5 particles calcinated at 500 °C, 600 °C, and 700 °C.
Processes 13 01857 g004
Processes 13 01857 g005
Figure 5. EIS Nyquist diagram for DSSC produced with Nb2O5 particles calcinated at 500 °C, 600 °C, and 700 °C.
Figure 5. EIS Nyquist diagram for DSSC produced with Nb2O5 particles calcinated at 500 °C, 600 °C, and 700 °C.
Processes 13 01857 g005
Table 1. Particle size and zeta potential under ethanol solution of Nb2O5 particles produced by Pechini methodology at 500 °C, 600 °C, and 700 °C.
Table 1. Particle size and zeta potential under ethanol solution of Nb2O5 particles produced by Pechini methodology at 500 °C, 600 °C, and 700 °C.
Temperature (°C)Particle Size
Diameter (nm)		Zeta Potential (mV)
500827.63 ± 26−25.53 ± 2.84
600642.17 ± 37−8.27 ± 0.32
7001022.57 ± 46.8−20.43 ± 1.33
Table 2. Photovoltaic parameters for DSSC prepared with Nb2O5 particles calcinated at 500 °C, 600 °C, and 700 °C.
Table 2. Photovoltaic parameters for DSSC prepared with Nb2O5 particles calcinated at 500 °C, 600 °C, and 700 °C.
Temperature (°C)Jsc (mA cm−2)Voc (V)FFPCE (%)
5003.190.7380.4811.13
6004.230.6940.4741.39
7001.360.7510.5360.55
DSSC was prepared using N719 as a dye in ethanolic solution (1 × 10−4 M), with a Pt electrode and an iodine-based electrolyte. The incident power was 100 mW cm−2.
Table 3. Solar cell resistances produced with Nb2O5 in different temperatures, obtained by Nyquist fitted diagram.
Table 3. Solar cell resistances produced with Nb2O5 in different temperatures, obtained by Nyquist fitted diagram.
Temperature (°C)RS (Ω)RCT (Ω)RCE (Ω)
50041.9305.084.7
60013.566.4349.0
7006.57736.0246.0
RCT represents charge transport resistance; RS represents series resistance; and RCE represents counter electrode resistance.
Disclaimer/Publisher’s Note: The statements, opinions and data contained in all publications are solely those of the individual author(s) and contributor(s) and not of MDPI and/or the editor(s). MDPI and/or the editor(s) disclaim responsibility for any injury to people or property resulting from any ideas, methods, instructions or products referred to in the content.

Share and Cite

MDPI and ACS Style

Davi, R.L.C.; Almeida, E.A.d.; Peron, A.P.; Banczek, E.d.P.; Junior, O.V.; Tractz, G.T. From Structure to Efficiency: Unveiling the Role of Calcination Temperature in Nb2O5-Based DSSCs. Processes 2025, 13, 1857. https://doi.org/10.3390/pr13061857

AMA Style

Davi RLC, Almeida EAd, Peron AP, Banczek EdP, Junior OV, Tractz GT. From Structure to Efficiency: Unveiling the Role of Calcination Temperature in Nb2O5-Based DSSCs. Processes. 2025; 13(6):1857. https://doi.org/10.3390/pr13061857

Chicago/Turabian Style

Davi, Ronald Luiz Castiglioni, Edson Araujo de Almeida, Ana Paula Peron, Everson do Prado Banczek, Osvaldo Valarini Junior, and Gideã Taques Tractz. 2025. "From Structure to Efficiency: Unveiling the Role of Calcination Temperature in Nb2O5-Based DSSCs" Processes 13, no. 6: 1857. https://doi.org/10.3390/pr13061857

APA Style

Davi, R. L. C., Almeida, E. A. d., Peron, A. P., Banczek, E. d. P., Junior, O. V., & Tractz, G. T. (2025). From Structure to Efficiency: Unveiling the Role of Calcination Temperature in Nb2O5-Based DSSCs. Processes, 13(6), 1857. https://doi.org/10.3390/pr13061857

Note that from the first issue of 2016, this journal uses article numbers instead of page numbers. See further details here.

Article Metrics

Back to TopTop