In this study, we investigated the fabrication, properties, and sensing applications of TiO₂ nanotubes. A pure titanium metal sheet was used to demonstrate how titanium dioxide nanotubes can be used for gas-sensing applications through the electrochemical anodization method. Subsequently, X-ray diffraction indicated the crystallization of the titanium dioxide layer. Scanning electron microscopy and transmission electron microscopy then revealed the average diameter of the TiO₂ nanotubes to be approximately 100 nm, with tube lengths ranging between 3 and 9 µm and the thickness of the nanotube walls being about 25 nm. This type of TiO₂ nanotube was found to be suitable for NO₂ gas sensor applications. With an oxidation time of 15 min, its detection of NO₂ gas showed a good result at 250 °C, especially when exposed to a NO₂ gas flow of 100 ppm, where a maximum NO₂ gas response of 96% was obtained. The NO₂ sensors based on the TiO₂ nanotube arrays all exhibited a high level of stability, good reproducibility, and high sensitivity.

This study explored advancements in photovoltaic technologies by enhancing the electronic quality of multicrystalline silicon (mc-Si) through silicon nitride (SiN_x) and hydrogen (H₂) plasma deposition via plasma-enhanced chemical vapor deposition (PECVD). This innovative approach replaced toxic chemical wet processes with H₂ plasma and SiN_x. The key parameters of silicon solar cells, including the effective lifetime (τ_eff), diffusion length (L_diff), and iron concentration ([Fe]), were analyzed before and after this sustainable solution. The results show significant improvements, particularly in the edge region, which initially exhibited a low τ_eff and a high iron concentration. After the treatment, the τ_eff and L_diff increased to 7 μs and 210 μm, respectively, compared to 2 μs and 70 μm for the untreated mc-Si. Additionally, the [Fe] decreased significantly after the process, dropping from 60 ppt to 10 ppt in most regions. Furthermore, the treatment led to a significant decrease in reflectivity, from 25% to 8% at a wavelength of 500 nm. These findings highlight the effectiveness of the PECVD-SiN_x and H₂ plasma treatments for improving the optoelectronic performance of mc-Si, making them promising options for high-efficiency photovoltaic devices.

In this study, we investigated and compared the influence of alumina nanoparticles (Al-NPs) and silicon nitride (SiN_x) layers individually deposited on multi-crystalline silicon (mc-Si) on mc-Si’s structural, optical, and optoelectronic characteristics to improve surface quality. Alumina nanoparticle-covered multi-crystalline silicon, immersion in HF/H₂O₂/HNO₃, and porous silicon (PS) covered with a silicon nitride structure are key components in achieving high electronic quality in multi-crystalline silicon. Surface reflectivity decreased from 27% to a minimum value of 2% for alumina nanoparticles/PS and a minimum value of 5% for silicon nitride/PS at a wavelength of 930 nm. Meanwhile, the minority carrier diffusion length increased from 2 µm to 300 µm for porous silicon combined with silicon nitride and to 100 µm for alumina nanoparticles/porous silicon. Two-dimensional current mapping further demonstrated a considerable enhancement in the generated current, rising from 2.8 nA for untreated mc-Si to 34 nA for Al-NPs/PS and 66 nA for PS/SiN_x. These results confirm that the surface passivation of mc-Si using Al-NPs or PS combined with SiN_x is a promising and efficient method to improve the electrical quality of mc-Si wafers, contributing to the development of high-performance mc-Si-based solar cells.

Surface texturing is vital for enhancing light absorption and optimizing the optoelectronic properties of multicrystalline silicon (mc-Si) samples. Texturing significantly improves light absorption by minimizing reflectance and extending the effective path length of incident light. Furthermore, porous silicon treatment on textured mc-Si surfaces offers additional advantages, including enhanced carrier generation, reduced surface recombination, and improved light emission. In this study, a dual treatment combining porous silicon and texturing was employed as an effective approach to enhance the optical and optoelectronic properties of mc-Si. Both porous silicon and texturing were achieved through a chemical etching process. After these surface modifications, the morphology and structure of mc-Si were examined using Atomic Force Microscopy (AFM), Scanning Electron Microscopy (SEM), UV-Vis-IR spectroscopy, photoluminescence (PL), WCT-120 photo-conductance lifetime measurements, and Two-Internal Quantum Efficiency (IQE) analysis. The results reveal a substantial improvement in the material’s properties. The total reflectivity dropped from 35% to approximately 5%, while the effective minority carrier lifetime increased from 2 µs for bare mc-Si to 36 µs after treatment. Additionally, the two-dimensional IQE value rose from 35% for the untreated sample to 66% after treatment, representing an enhancement of around 31%. These findings highlight the potential of surface engineering techniques in optimizing mc-Si for photovoltaic applications.

In this work, we present a gettering technique for multicrystalline silicon (mc-Si) by combining a nanowire structure with thermal treatment under nitrogen in an infrared lamp furnace. The silicon nanowires were elaborated using the Silver Nanoparticles Chemical Etching (Ag-NPsCE) technique. The optimal conditions for achieving effective gettering were determined based on the minority carrier lifetime (τ_eff) measurements. The results show τ_eff as a function of the gettering temperature and etching time, both before and after the removal of Ag nanoparticles using HNO₃. In both cases, the surface was identically treated with a 10% HF dip immediately prior to the carrier lifetime measurements. The highest τ_eff value, prior to Ag removal, was obtained after an etching duration of 3 min and was 6 µs at an excess carrier density Δn = 1 × 10¹⁴ cm⁻³. Moreover, τ_eff improves after silver removal. Therefore, removing Ag atoms using an aqueous HNO₃ solution is necessary to prevent this issue. Following Ag nanoparticle removal, τ_eff further increases, reaching 19 µs at a gettering temperature of 850 °C. Similarly, the electrical conductivity (ρ) and carrier mobility (μ) improve significantly after gettering, where the resistivity increases from 5.5 Ω·cm for the reference mc-Si to 1.9 Ω·cm, and the mobility rises from 122 cm²·V⁻¹·s⁻¹ to 253 cm²·V⁻¹·s⁻¹ after nanowire-based gettering at 850 °C. Overall, this method provides a scalable, practical, and cost-effective route to optimize mc-Si for high-performance photovoltaic applications.

This study explores advancements in photovoltaic technologies by enhancing the optoelectronic properties and electronic quality of multicrystalline Silicon (mc-Si) through silicon nitride (SiNx) and hydrogen (H2) plasma deposition via Plasma-Enhanced Chemical Vapor Deposition (PECVD). This innovative approach replaces toxic chemical wet processes with H2 plasma and SiNx, promoting environmentally friendly and sustainable energy solutions. Key parameters of silicon solar cells, including effective lifetime (τeff), diffusion length (Ldiff), in addition to the iron concentration ([Fe]), were analyzed before and after this sustainable solution. The results show significant improvements, particularly in the edge region, which initially exhibited low τeff and a high iron concentration. After treatment, τeff and Ldiff increased to 7 μs and 210 μm, respectively, compared to 2 μs and 70 μm for untreated mc-Si. Additionally, the [Fe] decreased significantly after the process, dropping from 60 ppt to 10 ppt in most regions. Furthermore, the treatment led to a significant decrease in reflectivity, from 25% to 8% at a wavelength of 500 nm. These findings highlight the effectiveness of PECVD-SiNx and H2 plasma treatments in improving the optoelectronic performance of mc-Si, making them promising for high-efficiency photovoltaic devices.