Achref Mannai

In this paper, we report on the effect of combining porous silicon with aluminum microparticles (PS/Al-µPs) on the optical and electronic properties of multicrystalline silicon (mc-Si). An aluminum film was deposited on the mc-Si surface, annealed at 750 °C for 20 min, and partially remained on the surface after CP₄ treatment. The surface was subsequently treated with a stain-etching solution (HF/HNO₃/H₂O) to form a porous silicon (PS) layer. The resulting mc-Si with PS/Al-µPs modification led to a marked improvement in the optoelectronic performance of the treated mc-Si. Surface reflectance was reduced from 34.6% to 9.1% across 400–800 nm wavelength range, corresponding to a 74% decrease. Minority carrier lifetime increased from 2 µs in untreated samples to 1 ms after Al-µPs passivation and remained elevated at 285 µs following stain etching. Additionally, the effective surface recombination velocity dropped from 50 cm·s⁻¹ to 0.35 cm·s⁻¹ and a reduction in [Fe] after treatment confirms the effectiveness of the PS-Al-µPs gettering process. FTIR analysis confirmed the formation of Si–H and Al–O bonds, highlighting effective surface passivation and suppression of recombination losses.

In this work, the impact of hydrogen plasma treatment on the electrical and electronic quality of multicrystalline silicon (mc-Si) was systematically investigated using plasma-enhanced chemical vapor deposition (PE-CVD). Hydrogen radicals generated in the plasma effectively passivate dangling bonds, reducing electrically active defects and enhancing material quality. Optimized PE-CVD conditions were applied to promote efficient hydrogen incorporation and surface modification. Optical characterization, including reflectivity measurements and FT-IR spectroscopy, confirms the formation of Si–H bonds and a significant reduction in surface reflectivity of up to 66% at 600 nm. Electrical and optoelectronic analyses reveal pronounced improvements in carrier lifetime and diffusion length, increased by 200% and 79%, respectively. In addition, dark current–voltage (I–V) measurements show a 32% decrease in series resistance and a 51% increase in shunt resistance, indicating enhanced charge transport and suppressed leakage currents. These macroscopic electrical improvements are supported by light beam-induced current (LBIC) measurements, which demonstrate a 14% increase in grain boundary current, confirming effective hydrogen passivation and reduced recombination. Overall, hydrogen plasma PE-CVD treatment is shown to significantly improve the electronic quality and photovoltaic performance of mc-Si solar cells.

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 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.

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 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.

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.

Surface texturing is vital in 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 photoconductance lifetime measurements, and Internal Quantum Efficiency (IQE) analysis. 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 to 36 µs. Additionally, the two-dimensional IQE value rose from 31% for the untreated sample to 63% after treatment, representing an enhancement of around 26%. These findings highlight the potential of surface engineering techniques in optimizing mc-Si for photovoltaic applications.

In this paper, we compared the effects of alumina nanoparticles and silicon nitride layer deposited on multi-crystalline silicon separately of structure, optic, and optoelectronic properties, to achieve excellent surface. Alumina nanoparticles -covered mc-Si immersion in HF/H2O2/HNO3 and porous silicon covered with silicon nitride structure are the key factors to achieving a high electronic quality of multi-crystalline silicon. Consequently, the surface reflectivity decreases from 35% to 2% for alumina nanoparticles/PS and to 5% for silicon nitride/PS in the wavelength range of 250–1200 nm. Meanwhile, the minority carrier diffusion length increases from 2 µm to 300 µm for PS combined with SiNx and to 100 µm for alumina nanoparticles/PS. Furthermore, the Two-Dimensional Produced Current measurement shows a significant enhancement compared to bare mc-Si (2.8 nA), reaching a maximum of 34 nA for alumina nanoparticles/PS and 66 nA for PS combined with SiN. These results indicate that multi-crystalline silicon surface passivation using aluminum/PS or PS combined with SiNx is an effective approach to enhancing the electronic quality of mc-Si wafers, thereby improving the efficiency of mc-Si-based solar cells.