Enhancement of Optical Properties in In 2 O 3 -Doped PVA/PEG Nanostructured Films for Optoelectronic Applications

ABSTRACT


INTRODUCTION
Nanocomposite films, characterized by a polymer matrix, have emerged as materials of significant interest across various scientific disciplines.Their notable properties encompass a range of attributes including optical, magnetic, thermal, electrical, and mechanical aspects.Recent advancements have focused on the development and properties of these nanocomposite-based polymer films, particularly for their application in light-stable color filters, solar cells, and optical sensors [1].The composite materials, especially those incorporating a polymer matrix, have been extensively explored for electrical applications due to their flexible nature and ease of fabrication [2,3].
Recent advancements in the field of material science have witnessed a significant surge in the development of polymerbased composites.These materials have been extensively explored due to their versatility, cost-effectiveness, and ease of fabrication.Polymers, traditionally seen as inexpensive and easily malleable materials, have found widespread applications, particularly in the realm of composites.The integration of polymer matrices with ceramic additives has led to composites that exhibit enhanced reflectivity, proving beneficial in various electrical and electronic applications.Such composites have been employed in diverse domains, including the manufacturing of angular acceleration accelerometers, integrated decoupling capacitors, acoustic emission sensors, and electronic packaging.Organic polymers are prized for their ease of shaping, flexibility, durability, and lightweight nature.In contrast, ceramics are renowned for their exceptional optical, mechanical, and thermal resistance properties.In recent years, alongside metals and alloys, ceramic-polymer composites have emerged as a prominent class of high-performance engineering materials.The characteristics of these composites, such as the distribution of reinforcement or filler within the matrix and the adhesion phenomena between the filler and the matrix, are crucial in determining the final properties of the composite [4,5].
Organic polymers are typically insulating, yet capable of accumulating electronic charge.Composites have become pivotal in contemporary material science due to their combination of desirable characteristics: lightweight, corrosion resistance, high fatigue strength, and ease of assembly.These materials find applications in the construction of aircraft, medical devices, spacecraft, and domestic buildings, providing extraordinary combinations of material properties [6].PVA is recognized for its biocompatibility, biodegradability, and excellent barrier properties.Its versatility has led to its use in industries ranging from food to textiles, and as a carrier for drug delivery systems.PVA is known for its good physical properties, non-toxicity, and biodegradability [7][8][9].PEG is similarly valued for its solubility in water and low toxicity, making it a preferred material in biotechnical applications [10].Indium oxide (In2O3), a widely used n-type semiconductor with an energy gap of 3.6 eV, has garnered attention due to its unique optical, chemical, and electrical properties [11].Nanocomposites have found applications across a broad spectrum of fields, including antibacterial [12][13][14], energy storage [15][16][17][18], electronics [19,20], and as components in piezoelectric and sensor technologies [21][22][23][24].This study delves into the fabrication of blend/In2O3 nanostructures and examines their optical characteristics for potential use in various optical fields.

MATERIALS AND METHODS
The casting procedure was used to create nanostructure films of PVA/PEG in varied ratios of In2O3 nanostructures. 1 g of polymers dissolved in distilled water (30 ml) yields a blend solution of PVA and PEG in a ratio of 70% PVA and 30% PEG.The In2O3 NPs were added to the mix solution (PVA/PEG) at 1%, 2%, and 3% concentrations.The optical properties of blend/In2O3 nanostructures films were evaluated using a Shimadzu UV-18000A spectrophotometer.Absorption coefficient, α is defined by the study [25]: where, A denotes to absorbance and d denotes to thickness.The energy gap is determined by the study [26]: where, G represents a constant, hυ represents the energy of photon, Eg denotes to band gap, m = 2 and 3 to transitions of allowed and forbidden.Refractive index(n) is given by the study [27]: where, R is the reflectance.The extinction coefficient (k) is determined by the study [28]: where, λ is the wavelength.

RESULTS AND DISCUSSION
A material's optical and electrical characteristics are intertwined; in electromagnetic theory, for instance, the high frequency permittivity and the optical refractive index, n, are associated.The absorption of optical light occurs through electron rearrangements within molecules, particularly in the visible and ultraviolet range, as well as by the activation of bond vibrations in the infrared range.Scattering events [31] have a significant impact on optical properties.Given that the polymer materials possess microstructural features that align with the size of optical wavelengths, the phenomenon of light scattering serves as a clear manifestation of optical diffraction processes [32].The majority of polymers lack color due to the fact that only a small fraction of pure polymers have the ability to absorb photons within the visual range, which spans from around 380 to 760 nm [33].Their brownish appearance in reflected light is due to their significant absorption of blue light.Chromophores are organic compounds with aromatic rings or alternating double and single covalent bonds.At frequencies corresponding to the excitation energy of the bonding electrons, they absorb light.To add pigments or dyes to polymer materials in order to give them a certain hue.The hues of solid polymers can be fully identified by analyzing their spectra, either through transmission or reflection if applicable [34].While certain polymers may not absorb light within the visible spectrum, it is widely understood that they do exhibit significant light absorption at specific infrared frequencies.Infrared spectroscopy is a highly effective technique for analyzing polymers, enabling the straightforward identification of polymer compounds with unknown composition using small samples.The molecular structure of a polymer determines its infrared spectrum, which can be characterized by either transmission or reflectance [35].
Figure 1 depicts the absorption of films made from PVA/PEG/In2O3 nanostructures.The absorption intensity of the PVA/PEG increases with an increase in the content of In2O3 NPs.This is attributed to the higher density of charge carriers, resulting in higher absorbance values [36,37].Consequently, the transmittance decreases, as illustrated in Figure 2. Furthermore, when the wavelength of photons rises, the absorbance falls and the transmittance increases.The PVA/PEG/In2O3 nanostructure films exhibit a significant level of absorption in the UV-spectrum.Understanding the absorption coefficient is helpful for determining the nature of a transition.Figure 3  The pristine sample exhibited a diminished absorbance coefficient, potentially attributable to its reduced crystallinity [38].
Figures 4 and 5 illustrate the energies gaps values of PVA/PEG/In2O3 nanostructures films of allowed and forbidden transitions.Because of the formation of levels in the band gap, the blend's Eg value lowers as the concentration of In2O3 NPs rises.Moreover, the noncrystalline phase of the composite polymer experiences local cross-linking [39][40][41][42][43][44][45][46][47].The refractive index and extinction coefficient performances of blend/In2O3 nanostructures films are showed in Figures 6 and 7.The values of n and k of blend rise when the In2O3 NPs ratio increases, these behaviors due to rise in the density of films and α values [48][49][50][51][52].The influence of In2O3 NPs content on conductivity of blend/In2O3 nanostructures films is represented in Figure 10.The σop value of PVA/PEG/In2O3 nanostructures films rises with rise in the In2O3 NPs content and this behavior related to rise in the absorption and reduce in the energy gap [59][60][61][62][63][64].
illustrates the alpha (α) values of PVA/PEG/In2O3 nanostructure films.The Figure shows α values of 104 cm-1, which correspond to indirect transitions.