Fabrication of WO₂I₂/Poly(o-Aminothiophenol) Porous Spherical Nanocomposite and Its Application in Photodetectors

Background Introduction

In recent years, photodetectors have garnered significant attention due to their wide applications in fields such as lighting and aerospace technology. However, traditional metal oxide-based photodetectors often face challenges such as low sensitivity and limited spectral response ranges. For instance, studies on materials like ZnO/Cu₂O and Se/TiO₂ have shown that their photoresponse is mainly concentrated in the ultraviolet region, with a photoresponsivity ® typically below 0.001 mA/W. Additionally, polymer materials such as P3HT and PBbTPD:tri-PC61BM, despite their good conductivity and low-cost advantages, still exhibit relatively low photoresponsivity (around 0.01 mA/W). Therefore, developing a new type of photodetector material with high sensitivity, broad spectral response, and low cost has become a research hotspot.

Against this backdrop, Fatemah H. Alkallas et al. proposed a photodetector based on a porous spherical nanocomposite of WO₂I₂/poly(o-aminothiophenol) (WO₂I₂/PoATP). This study aims to combine the advantages of inorganic materials (WO₂I₂) with organic polymers (PoATP) to address the shortcomings of existing photodetectors in terms of sensitivity, spectral response range, and cost. Furthermore, the authors hope to enhance its optoelectronic performance by optimizing material structural design.

Source of the Paper

This paper was co-authored by Fatemah H. Alkallas, Amira Ben Gouider Trabelsi, Tahani A. Alrebdi, and Mohamed Rabia. The first author and corresponding author are affiliated with the Department of Physics, College of Science, Princess Nourah Bint Abdulrahman University, Saudi Arabia, and the Chemistry Department, Faculty of Science, Beni-Suef University, Egypt, respectively. The paper was accepted on December 13, 2024, and published in the journal Optical and Quantum Electronics, with the article number 57:150.

Research Workflow and Experimental Methods

Experimental Materials and Synthesis Methods

The raw materials used in this study include o-aminothiophenol (99.9%), sodium tungstate (Na₂WO₄, 99.8%), acetic acid (CH₃COOH, 99.9%), iodine (I₂, 99.9%), and potassium iodide (KI, 99.8%). The fabrication of the WO₂I₂/PoATP porous spherical nanocomposite thin film was carried out in two steps: First, o-aminothiophenol was dissolved in acetic acid and reacted with an iodine solution to form I-PoATP through an oxidation reaction. Subsequently, I-PoATP was reacted with Na₂WO₄ via a double displacement mechanism to form the WO₂I₂/PoATP nanocomposite thin film. The final thin film was deposited on a glass substrate for subsequent characterization and testing.

Characterization and Testing Methods

Material Characterization

1. Fourier Transform Infrared Spectroscopy (FTIR): Analyzed the chemical composition and functional group changes of the WO₂I₂/PoATP nanocomposite.
2. X-ray Diffraction (XRD): Determined the crystal structure and grain size of the material.
3. X-ray Photoelectron Spectroscopy (XPS): Investigated the elemental composition and oxidation states of the material.
4. Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM): Observed the morphological features and pore distribution of the material.

Optoelectronic Performance Testing

Optoelectronic performance testing was conducted using a CHI608E electrochemical workstation. Both sides of the sample were coated with silver paste and connected to the workstation, followed by linear sweep voltammetry testing within a voltage range of -2 to 2 V. A vacuum metal halide lamp was used as the light source, providing full-spectrum white light illumination. By measuring the dark current density (Jo) and photocurrent density (Jph), the photoresponsivity ® and detectivity (D) were calculated.

Data Analysis Algorithms

The formulas for calculating photoresponsivity ® and detectivity (D) are as follows: - ( R = \frac{J_{ph} - J_d}{P} ) - ( D = \frac{R \sqrt{A}}{2eJ_o} )

Here, ( J_{ph} ) and ( J_o ) represent the current densities under illuminated and dark conditions, respectively, ( P ) is the light intensity, ( A ) is the device area, and ( e ) is the electron charge.

Main Results and Discussion

Chemical and Structural Properties

FTIR analysis revealed that the absorption peaks of the WO₂I₂/PoATP nanocomposite exhibited a redshift compared to pure PoATP, indicating strong interactions between inorganic WO₂I₂ and organic PoATP. XRD tests identified ten characteristic diffraction peaks of WO₂I₂, with a crystallite size of 121 nm. XPS data further confirmed the presence of W and I and their oxidation states.

Morphology and Optical Properties

SEM and TEM images showed that the WO₂I₂/PoATP nanocomposite had a porous spherical structure with pore diameters of approximately 5 nm. Optical tests demonstrated that the material possessed broad-spectrum absorption capabilities (extending into the near-infrared region) and a bandgap of only 2.0 eV. These characteristics enable it to efficiently capture and utilize photons.

Optoelectronic Performance

Under white light illumination, the photocurrent density of the WO₂I₂/PoATP nanocomposite thin film was 0.32 mA/cm² (( J_{ph} = 0.8 \, \text{mA/cm}^2 ), ( J_o = 0.48 \, \text{mA/cm}^2 )). As the wavelength decreased from 540 nm to 340 nm, the photoresponsivity ® increased from 7.2 mA/W to 8.0 mA/W, while the detectivity (D) rose from ( 0.164 \times 10^{10} \, \text{Jones} ) to ( 0.181 \times 10^{10} \, \text{Jones} ). Even at a wavelength of 730 nm, R and D remained at 6.4 mA/W and ( 0.145 \times 10^{10} \, \text{Jones} ), respectively.

Stability and Reproducibility

Repeated tests showed that the photocurrent density of the device exhibited extremely high stability, with minimal standard deviation. Additionally, the device’s response time to light signals was approximately 1 second, with a decay time of 3.5 seconds, demonstrating excellent dynamic performance.

Conclusions and Significance

Scientific Value

This study successfully fabricated a novel WO₂I₂/PoATP porous spherical nanocomposite and verified its potential as an efficient photodetector. The material not only exhibits broad-spectrum absorption capabilities and a low bandgap but also demonstrates excellent photoresponsivity and detectivity.

Application Value

Due to its high sensitivity, broad spectral response, low cost, and ease of mass production, this material holds great promise for industrial applications, particularly in ultraviolet, visible, and infrared light detection.

Research Highlights

1. Material Innovation: The combination of WO₂I₂ with PoATP for the first time achieved a synergistic effect in inorganic-organic composite materials.
2. Performance Breakthrough: The photoresponsivity and detectivity significantly outperform existing materials, addressing the limitations of traditional photodetectors.
3. Simple Process: The preparation method is straightforward and cost-effective, suitable for industrial production.

Summary

This study not only provides a new material option for the field of photodetectors but also demonstrates the enormous potential of inorganic-organic composite materials in optoelectronic devices. In the future, this material is expected to play a significant role in environmental monitoring, communication technology, and energy conversion.