Green Energy from Hen Feathers Dye: A Promising Approach for Sustainable Solar Cells

1. Introduction:

The production of chicken meat results in the generation of various types of waste, with feathers being one of the most notable examples, according to several authors [1,2,3]. Billions of tons of feathers are produced globally, posing a significant issue as they are waste materials that impact both public health and the environment [4]. Feathers are primarily generated in chicken processing plants and poultry farms, accounting for a substantial source of pollution, as they make up about 5% to 10% of the total weight of the chicken [5]. In Mexico, it was estimated that the total chicken consumption would reach 3,274 million tons in 2018 [6]. This implies that approximately 163.7 to 327.4 million tons of feathers will be produced. Some research into solutions to reduce or eliminate the contamination issue suggests incorporating feathers as a feed supplement, as 95% of their dry weight consists of protein, with 90% being keratin [7]. Over the past two decades, advancements in photovoltaic technologies have led to the emergence of innovative devices known as "emerging photovoltaics." These technologies aim to reduce module costs and expand the applicability of photovoltaics to compete with other energy production systems. Among these new technologies, those utilizing alternative materials that mimic photosynthesis by leveraging the ability of organic dyes to generate electron–hole pairs have attracted significant interest for their potential as viable alternatives to traditional inorganic semiconductor-based devices. A prominent example in this category is dye-sensitized solar cells (DSSCs), with the first official reference appearing in a U.S. patent filed in 1977 [8]. However, it was the work of Professor Michael Gratzel on metal oxide sensitization during the 1980s that laid the foundation for the first efficiently assembled DSSC. This breakthrough, achieved in 1991, involved the innovative use of a nanoscopic titanium dioxide (TiO₂) particle layer combined with a polypyridyl complex of ruthenium as the light-absorbing material [9]. In a DSSC, light is captured by a photosensitizer on a thin layer of nanocrystalline semiconductor (usually TiO₂) at the anode. The photosensitizer transfers an electron to the semiconductor, which moves to the back contact, while the oxidized dye is regenerated by a redox couple at the cathode. The connection between electrodes generates electric current. DSSCs are appealing for their low-cost materials, compatibility with various substrates and printing techniques, and ability to perform well in diffuse light and high temperatures. Unlike conventional photovoltaics, they separate functions like light absorption, charge generation, and transport across different components, allowing for greater optimization based on the Shockley–Queisser limit [10]. Light harvesting is the initial step in the processes that generate power in DSSCs. The wide-bandgap semiconductor TiO₂ is photochemically stable, making it suitable for cathode fabrication; however, its spectral sensitivity is confined to the UV range. Therefore, a light-absorbing sensitizer must be adsorbed onto the semiconductor's surface [11]. DSSC sensitizers must have a broad absorption spectrum, high stability (20-year lifespan), strong semiconductor anchoring, and low toxicity and cost. Recent advances have improved their efficiency and durability [12,13,14].

2. Materials and Method:

The preparation of dye-sensitized solar cells (DSSCs) involved several steps. First, a TiO₂ thin film was prepared on FTO-coated glass using a sol-gel method and sintered in Muffle furnace to form a mesoporous layer (180-210 nm). Next, natural dye was extracted from ground Hen feathers by immersing them in a 1N NaOH solution, followed by filtration and centrifugation to obtain a clear dye solution. The TiO₂ film was soaked in the dye solution overnight and dried to create the dye-sensitized TiO₂ film. Finally, a 0.1 M Na₂SO₄ electrolyte solution was prepared for photovoltaic analysis [15,16,17,18].

3. Result and Discussion:

Characterization Techniques:

3.1 Xrd Analysis:

X-ray diffraction (XRD) in Figure 1 revealed that TiO₂ nanoparticles, after calcination at 500°C, exhibited distinct anatase phase peaks, confirming good crystallinity. The peaks at 2ϴ values of 25.41°, 37.80°, 48.19°, 54.14°, 55.18°, 62.87°, 69.03°, 70.45°, and 75.27° correspond to the anatase TiO₂ phase. The HFD + TiO₂ film showed prominent peaks at (101), (200) and (211), suggesting strong interaction with the HFD matrix while retaining the anatase phase, which enhances its structural and functional properties [19,20].

Table 1. XRD analysis for HFD + TiO₂ films.

Sample	FWHM Value	Crystallite size (nm)	Dislocation density (Ꟙ) ($\mathbf{line}{\mathbf{M}}^{-2}\times$ 1014)	Microstrain (${\mathbf{line}}^{-2}{\mathbf{M}}^{-4}\times$ 10−4)
HFD + TiO2	0.21424	40.12	6.24	9.03

Table 1. XRD analysis for HFD + TiO₂ films.

Sample	FWHM Value	Crystallite size (nm)	Dislocation density (Ꟙ) ($\mathbf{line}{\mathbf{M}}^{-2}\times$ 1014)	Microstrain (${\mathbf{line}}^{-2}{\mathbf{M}}^{-4}\times$ 10−4)
HFD + TiO2	0.21424	40.12	6.24	9.03

3.2. UV Visible Analysis:

UV-visible spectroscopy analyzed the optical properties of TiO₂ and HFD + TiO₂ thin films in Figure 2. HFD + TiO₂ absorbed in the 200-450 nm range, with a reduced band gap of 2.27 eV compared to 3.21 eV for bare TiO₂. The band gap reduction, confirmed by the Tauc plot, suggests enhanced light absorption due to electronic interactions, making the material more effective for photocatalysis and optoelectronic applications [21].

3.3. Ftir Analys:

FTIR analysisin in Figure 3 confirms Pheomelanin's structure in hen feather dye, with peaks at 546.38 cm⁻¹ (S=O stretching), 1000–1157 cm⁻¹ (C-O stretching), 1157 & 1237–1384 cm⁻¹ (C-N stretching), 1447–1643 cm⁻¹ (aromatic C-H & C=C stretching) and 2855–3419 cm⁻¹ (O-H & aliphatic C-H stretching), indicating sulfur, aromatic, hydroxyl, and polymeric groups. These findings indicate that the hen feather dye contains sulfur, aromatic, hydroxyl, and polymeric groups, supporting its classification as a pheomelanin-based pigment with potential applications in sustainable and natural dye formulations [22,23].

3.4. NMR Analysis:

NMR analysis in Figure 4 verifies pheomelanin’s structure with peaks at 0.8 ppm (CH₃-S), 1.2 ppm (CH₂ backbone), 2.5 ppm (CH₂-quinone), 3.3 ppm (CH-OH), and 8.1 ppm (Ar-H in benzothiazine/quinone), confirming its sulfur-containing, aromatic, and polymeric nature, suitable for dye applications [24].

3.5. SEM Analysis:

The morphology of HFD + TiO₂ thin film synthesized via the sol-gel method was analyzed using SEM. Figure 5 low and high magnified images reveal that calcined HFD + TiO₂ thin film (500°C, 1 hour) exhibits predominantly spherical, non-uniform particles that form aggregates. The estimated average particle size of HFD + TiO₂ thin film is approximately 113.93 nm. The nanostructured morphology may enhance photocatalysis, adhesion, and applications in coatings, sensors, or dye adsorption [25].

3.6. EDAX Analysis:

The EDAX analysis in Figure 6 identifies elements in HFD + TiO₂ thin film by measuring the kinetic energy of emitted electrons from specified SEM points.The respective kinetic energy for oxygen O and titanium atoms are 0.525 keV and 4.508 keV. Thus, the EDAX spectrum of titanium oxide nanoparticles indicates the presence of oxygen and titanium atoms and it also confirms that the produced nanoparticles in the photoanode films are TiO₂. From the data in Table of HFD+TiO₂, it is seen that, the mass percentage of HFD+TiO₂ obtained from EDAX analysis are 4% C, 0.28% N, 52.68% O, 0.94% S and 42.11% Ti. The atom percentages are 7.31% C, 0.44% N, 72.3% O, 0.64% S and 19.3% Ti. Thus, it is clear that the produced nano sized particles are TiO₂. EDAX analysis confirms the presence of TiO₂ nanoparticles in the HFD + TiO₂ thin film, with oxygen (52.68%) and titanium (42.11%) as major elements. The detected carbon, nitrogen, and sulfur suggest HFD incorporation, potentially modifying surface properties. This functionalization may enhance photocatalysis, dye adsorption, or charge transfer in applications like DSSCs [26].

3.7. AFM Analysis:

Bare TiO₂ has low RMS roughness, smaller grain size, and lower dye-loading efficiency, limiting DSSC performance. In contrast, HFD + TiO₂ in Figure 7 has higher RMS roughness, larger grain size, and a rougher surface, enhancing dye loading, light absorption, photocurrent, efficiency, and stability [27].

3.8. XPS Analysis:

XPS analysis was conducted to validate the electronic states of elements and their binding energies. Figure 8 shows the survey scan of HFD + TiO₂, highlighting key elemental peaks. The C1s peak appears at 288.86 eV (Figure 8a), while the N1s peak is observed at 403.63 eV (Figure 8b). The O1s peak, located at 534.0 eV (Figure 8c), contributes to enhancing the photocatalytic activity of the semiconductor oxide. The S 2p spectrum (Figure 8d) displays two peaks at 157.99 eV and 159.02 eV, corresponding to S 2p₁/₂ and S 2p₃/₂, with an energy separation of 1.03 eV, aligning with standard S 2p binding energies. Similarly, the Ti 2p spectrum (Figure 8e) features peaks at 462.47 eV and 468.44 eV, attributed to Ti 2p₃/₂ and Ti 2p₁/₂, confirming the presence of Ti⁴⁺ in TiO₂, with a separation of 5.97 eV, consistent with standard Ti 2p binding energies [28].

From the Spectroscopic and elemental analysis the structural representation of Pheomelanin dye present in the Hen feather is shown in below Figure 9 [29]:

3.9. PEC Analysis:

The study assessed the efficiency of dye-sensitized solar cells (DSSCs) using natural dye Pheomelanin's extracted from Hen Feathers as a sensitizer from Figure 10 shown in Table 2. TiO₂ nanocrystalline thin film was prepared using the sol-gel method. HFD + TiO₂ achieved an efficiency of 2.91% with a short-circuit current density (JSC) of 1.7 mA/cm² and an open-circuit voltage (VOC) of 421.78 mV. The improved efficiency of the HFD + TiO₂ DSSCs is attributed to the unique composition of the extracted dye, containing the pigment Pheomelanin's, which enhances light absorption and energy conversion [30].

4. Conclusion:

Pheomelanin, a dye derived from hen feathers, exhibits strong potential as a natural sensitizer for environmentally friendly and cost-effective dye-sensitized solar cells (DSSCs). A flexible and low-cost DSSC incorporating TiO₂, natural dyes, and a Na₂SO₄ electrolyte achieved an efficiency of 2.91%. The excellent photocatalytic properties of TiO₂ enhance its suitability for large-scale, sustainable DSSC manufacturing, making it promising for future industrial applications.