Pyramidal Silicon Research Articles

Tuning Perovskite Crystal Growth Dynamics Using Additives on Textured Silicon Substrates

Double‐sided textured silicon solar cells with micrometer‐sized pyramid structure are used as bottom cells in monolithic tandem structures to decrease reflection losses. As top cell material, frequently perovskites are used. In this work, various additives are investigated to enhance the perovskite absorber quality, as a top cell fabricated using the hybrid route. In the context of the hybrid route, it is found that urea or methylammonium chloride (MACl) can effectively increase the grain size and improve the absorber quality, while formamidinium chloride (FACl) cannot. With urea, the crystallization can be tuned without leaving any voids in the film (unlike MACl). However, when annealed at a high annealing temperature, the excessive crystal growth with urea causes non‐conformal coating and high defect density. By adjusting the annealing conditions and additive concentration, the crystal growth of the perovskite top cell on the micrometer‐sized silicon pyramids can be fine‐tuned, ensuring that the perovskite layer conformally coated the pyramids. The use of additives not only improves crystallization but also enhances the conversion of the inorganics, particularly at the hole transport layer (HTL) interface. Moreover, this work contributes to a better understanding of perovskite crystallization dynamics and how to control it, especially on textured substrates.

Enhanced solar hydrogen evolution by laminated integration of n+p-SiIP/TiO2/Pt inverted pyramid black Si photocathode

The nano/microstructuring of silicon (Si) via chemical methods has garnered significant attention due to its excellent light-trapping capabilities across a wide spectral range. Current research has predominantly focused on the synthesis of pyramidal-shaped microtextures, which enable two reflections on the surface, while largely overlooking the superior light-trapping potential of inverted pyramid silicon (SiIP) microtextures, which theoretically allow for three reflections. Moreover, there has been limited investigation into the application of inverted pyramid black silicon for solar-driven hydrogen evolution. This study reports the synthesis of uniformly arranged inverted pyramid-textured black silicon using the copper-assisted chemical etching (Cu-ACE) method to enhance the efficiency of solar-driven water splitting for hydrogen production. The formation mechanism and the influence of copper-localized surface plasmon resonance (Cu-LSPR) from Cu nanoparticle (NP) byproducts on photoelectrochemical (PEC) activity were systematically analyzed. To reduce sidewall defects and minimize photogenerated carrier recombination, the surface of the SiIP was treated with tetramethylammonium hydroxide (TMAH). A vertical PN junction was developed through ion implantation to reduce the external bias of the SiIP. Additionally, a uniform TiO₂ antireflective layer was deposited via atomic layer deposition (ALD), reducing the average reflectance of the SiIP-T4 to 5.78 % over the 300–1100 nm wavelength range. MoSₓ and Pt NPs were electrodeposited to improve the fill factor and enhance HER kinetics. With optimized catalyst loading, the n+p-SiIP-T4/TiO₂/Pt 80 mC electrode achieved a photocurrent density of 8.0 mA cm−2 at 0 V vs. RHE, an applied bias photon-to-current efficiency (ABPE) of 0.93 % at 0.24 V vs. RHE, and a double-layer capacitance (Cdl) of 91 μF cm−2. The onset potential (Von) was positively shifted by ∼1.13 V to 0.49 V vs. RHE compared to a SiIP photocathode, and the photocathode operated continuously at 0 V vs. RHE for 27 h in an acidic electrolyte. These results demonstrate that SiIP has significant potential for PEC hydrogen evolution, with further performance optimization achievable through structural and surface engineering.

Novel synthesis of 1-D silicon nanowires grown on pyramidal black silicon substrates and intense visible emission

This work shows a new way to grow 1-D Silicon Nanowires (SiNWs) over pyramidal black silicon used as substrates. These nanostructures are grown by the plasma-assisted vapor–liquid-solid (VLS) as a bottom-up process, using tin thin films as a catalytic metal and dichlorosilane gas as a silicon precursor. SiNWs were obtained with diameters from 300-600 nm and 4–6 µm lengths on the black silicon surface. Due to the pyramid-shaped and porous nature of the black silicon surface, SiNWs form a complex mesh nanostructure. This network has a large surface area and exhibits intense and effective photoluminescence with a peak in the green spectrum, which is attributed to the quantum confinement effect that occurred in small nc-Si embedded inside SiNWs. These structural configurations hold significant promise for applications in optical biosensors, solar cells, and other prospective fields.

Optimization of rear surface morphology in n-type TOPCon c-Si solar cells

Tunnel oxide passivated contact (TOPCon) crystalline silicon (c-Si) solar cells have attracted much attention because of their superior electrical properties such as the lower contact resistivity and better interface passivation at high temperatures. However, the TOPCon c-Si solar cells also have room for further improvement in optical performance, and the embodiment of optical advantages needs to be matched synchronously in electrical aspect. Here, the rear silicon pyramids with different angles have been achieved through solution corrosion to maximize the light absorption in the c-Si substrate. The light absorption for the pyramid angle of less than 30° is better. Compared with the cell samples with rear pyramid for a certain angle, the samples with flat back surface possess better surface passivation, and the contact resistivity can be reduced effectively by increasing the phosphorus doping concentration and adjusting the annealing temperature. Furthermore, the TOPCon c-Si solar cells with flat rear surface covered by 70 nm poly-Si have been demonstrated to increase the conversion efficiency by about 0.15 % vs. the counterpart for poly-Si of 130 nm thickness, and the improvement is mainly due to the increase of JSC and FF by 0.07 mA/cm2 and 0.72 %, respectively.

Purcell enhancement using spatially distributed random cavities enabled by silicon pyramid arrays

Purcell enhancement using spatially distributed random cavities enabled by silicon pyramid arrays

Light-trapping by wave interference in intermediate-thickness silicon solar cells

The power conversion efficiency of crystalline silicon (c − Si) solar cells have witnessed a 2.1% increase over the last 25 years due to improved carrier transport. Recently, the conversion efficiency of c − Si cell has reached 27.1% but falls well below the Shockley-Queisser limit as well as the statistical ray-optics based 29.43% limit. Further improvement of conversion efficiency requires reconsideration of traditional ray-trapping strategies for sunlight absorption. Wave-interference based light-trapping in photonic crystals (PhC) provides the opportunity to break the ray-optics based 4n 2 limit and offers the possibility of conversion efficiencies beyond 29.43% in c − Si cells. Using finite difference time domain simulations of Maxwell’s equations, we demonstrate photo-current densities above the 4n 2 limit in 50 − 300µm-thick inverted pyramid silicon PhCs, with lattice constant 3.1µm. Our 150µm-thick PhC design yields a maximum achievable photo-current density (MAPD) of 45.22mA/cm 2. We consider anti-reflection coatings and surface passivation consisting of SiO 2 − SiN x − Al 2 O 3 stacks. Our design optimization shows that a 80 − 120 − 150nm stack leads to slightly better solar light trapping in photonic crystal cells with thicknesses <50µm, whereas the 80 − 40 − 20nm stack performs better for cells with thicknesses >100µm. We show that replacing SiN x with SiC may improve the MAPD for PhC cells thinner than 100µm. For a fixed lattice constant of 3.1µm, we find no significant improvement in the solar absorption for 50 and 100µm-thick cells relative to a 15µm cell. A substantial improvement in the MAPD is observed for the 150µm cell, but there is practically no improvement in the solar light absorption beyond 150µm thickness.

Inverted Pyramidal Porous Silicon by Chemical Etching and PECVD Rebuilding for Selective Gas Sensing

Inverted Pyramidal Porous Silicon by Chemical Etching and PECVD Rebuilding for Selective Gas Sensing

Low‐Temperature Atomic Layer Deposition of Hole Transport Layers for Enhanced Performance and Scalability in Textured Perovskite/Silicon Tandem Solar Cells

AbstractPerovskite tandem solar cells on textured silicon hold potential for surpassing single‐junction limits and industrial compatibility. However, integrating hole‐transporting layers (HTLs) onto textured silicon poses challenges in conformal coating, low‐temperature fabrication, and perovskite solution process compatibility. Here, an atomic layer deposition (ALD) copper‐doping process is introduced to fabricate low‐temperature NiOx HTLs (ALD Cu:NiOx), tailored for textured tandems. Copper‐doping reduces hydroxyl group content and Ni3+ defects, addressing the challenge of enhancing hole conductivity while mitigating recombination loss. This advancement enables to lower the post‐annealing temperature from >300 to 200 °C, achieving compatibility with silicon heterojunction (SHJ) cells and boosting the power‐conversion efficiency (PCE) of 1.65‐eV p–i–n perovskite solar cells to 22.47%. Integrating ALD Cu:NiOx beneath conventional self‐assembled monolayer HTL on textured SHJ leads to notable PCE enhancements, from 28.6% to 30.5% for 1‐cm2 tandems (certified stabilized PCE of 30.04%) and from 23.9% to 26.4% for 8.89‐cm2 tandems. Following 1000 h of maximum‐power‐point (MPP) tracking, tandems maintain 95% of initial efficiency. Notably, losses in open‐circuit voltage and PCE due to area upscaling reduced by over 20%, attributed to ALD Cu:NiOx’s ability to enhance perovskite film wettability and minimize shunting on silicon pyramid texture, underscoring its impacts for textured tandem upscaling.

Silver Dendrite‐Coated Silicon Pyramid Substrate as Surface‐Enhanced Raman Scattering Probe for Detecting Glucose

Raman spectroscopy offers a rapid and nondestructive method for qualitatively and quantitatively analyzing the molecular structure of substances. Herein, a facile and cost‐effective approach for the preparation of three‐dimensional (3D) surface‐enhanced Raman scattering (SERS) substrates is proposed, in which pyramid structures are fabricated using silicon anisotropic wet etching and silver dendrites are decorated on these silicon pyramid (PSi) substrates by immersing them in a mixture of hydrofluoric acid and silver nitrate for several minutes. The 3D SERS substrates, based on PSi coated with Ag dendrites, reveal high‐performance SERS enhancement (with an analytical enhancement factor reaching 3.54 × 1010) and can detect rhodamine 6G (R6G) in the presence of chemical enhancer (lithium chloride) at low concentrations down to 10−11 m. For glucose detection, 2‐thienylboronic acid is employed to faciliate glucose attachment to the substrate surface, achieving a detection limit as low as 10−6 m. The substrate exhibits good repeatability with a relative standard deviation of 11.223%, as well as reusability and long‐term stability for detection. The results also highlight the excellent sensitivity of the PSi‐based SERS substrate, which is expected to be instrumental in biochemical analysis and holds significant potential for developing noninvasive glucose sensor for diabetic patients using saliva samples.

High-performance pyramid-SiNWs biosensor for NH3 gas detection

NH3 is widely existed in the environment and is closely associated with various health issues. Additionally, detecting the small amounts of NH3 exhaled by patients with liver and kidney diseases offers potential opportunities for painless early disease diagnosis. Therefore, there is an urgent need for a convenient, rapid, and highly sensitive real-time NH3 monitoring method. This work presents a high-performance NH3 sensor based on olfactory receptor-derived peptides (ORPs) on a pyramid silicon nanowires (SiNWs) structure substrate. First, we successfully fabricated the pyramid-SiNWs structure on a silicon substrate using a chemical etching method. Subsequently, by dehydrative condensation reaction between the amino groups on APTES and the carboxyl groups of ORPs, ORPs were successfully immobilized onto the pyramid-SiNWs structure. This methodology allows the ORPs sensor on the pyramid-SiNWs substrate to detect NH3 as low as 1 ppb, which was the reported lowest limit of detection, with a higher response rate compared to ORPs sensors on flat SiNWs substrates. The sensors also exhibit good sensitivity and stability for NH3 gas detection. The results show the feasibility and potential applications of ORPs-pyramid-SiNWs structure sensors, in the fields of food safety, disease monitoring, and environmental protection, etc.

Enhanced performance of poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate)/silicon solar cells employing inverted pyramidal silicon by one-step copper catalyzed etching

Here, micro-inverted pyramid structured silicon (Si) surface is prepared via simple yet effective, low-cost one-step copper catalyzed chemical etching (CuCCE) for superior light trapping. The inverted pyramidal (IP) arrays are obtained on large area of the partial polished (PP) Si surface by CuCCE in etch bath consisting of Cu(NO3)2/HF/H2O2 at 50 °C. The IP-Si shows significantly reduced total surface reflectance (<7%) than the PP-Si (>30%) for broad spectral range. Hybrid solar cells (HSCs), having junction between poly(3,4-ethylenedioxy thiophene):poly(styrene sulfonate)(PEDOT:PSS) and n-Si, are demonstrated on the IP-Si and PP-Si surfaces; named as IP-SC and PP-SC respectively. Direct enhancement of ∼3 fold in efficiency is observed for IP-SC than the PP-SC. The improved performance is attributed to enhanced light trapping ability of the IP-Si leading to the improved short circuit current density of ∼32 mA/cm2, ∼1.3 times higher than the PP-SC. The HSCs on CuCCE IP-Si surface is presented as a ‘proof of concept’ for future high efficiency devices.

High performance 3-methyl-1-butanol gas sensor based on olfactory receptor derived peptide on pyramidal-structure substrates

Detection of bacterial contamination in food is a critical issue for ensuring public health and safety. In response, we present a high-performing olfactory receptor-derived peptide (ORP) sensor for the detection of 3-methyl-1-butanol, a by-product produced by common meat-borne bacteria. Our approach involved the covalent attachment of ORPs to carbon nanotubes (CNTs) using a combination of pyramidal silicon substrate modification, thioester modification of CNTs, and chemical ligation of n-terminus cysteine-modified ORPs. The resulting sensor showed remarkable sensitivity with a detection limit of 0.0001 ppt—three orders of magnitude lower than previous reports. Moreover, our results demonstrate the sensor's selectivity and stability, making it a promising tool for a variety of applications, including food safety, medical detection, and environmental protection.

Retraction Note to: Sol–gel synthesis of silicon carbide on silicon pyramids: a promising candidate for supercapacitor electrodes

Retraction Note to: Sol–gel synthesis of silicon carbide on silicon pyramids: a promising candidate for supercapacitor electrodes

Photoelectrochemical properties of Cu2O/PANI/Si-based photocathodes for CO2 conversion

The present study was aimed at converting carbon dioxide (CO2) into value-added products such as methanol, which can provide not only a potential solution for controlling the carbon dioxide concentration level in the atmosphere but also can offer an alternative approach for the production of renewable energy sources. From this perspective, various hybrid photoelectrocatalysts were synthesized, characterized and used as photocathodes for photoelectrochemical (PEC) reduction of carbon dioxide to methanol in an aqueous medium under visible light irradiation. Flat silicon (Si) and pyramidal textured silicon (SiPY) substrates, covered with polyaniline (PANI) with or without sensitization with copper (I) oxide (Cu2O) particles, were investigated. It was observed that the combination of PANI and copper (I) oxide greatly increased PEC carbon dioxide reduction to methanol owing to the enhancement in the carbon dioxide chemisorption capacity by the photocathode surface and at the same time facilitated the separation of photogenerated electron–hole (e−/h+) pairs. The PEC results demonstrated that the applied potential impacts the photocurrent stability. Sensitization with copper (I) oxide effectively separated the photogenerated e−/h+ pairs and, therefore, enhanced the PEC carbon dioxide reduction activity of the hybrid photocatalyst. The best faradaic efficiency for methanol formation reached 57.66%, which was recorded when the copper (I) oxide/PANI/SiPY heterostructure was used as a photocathode at an applied potential of −1.2 V against the saturated calomel electrode.

Bonding III–V/Textured‐Silicon Monolithic Flexible Tandem Devices

AbstractIII–V/silicon tandem solar cells simultaneously have the potential advantages of high efficiency and low cost. Bonding is an effective way to realize tandem at both ends. However, it is difficult to realize vacuum bonding in industrialized micrometer‐sized pyramid silicon cells. Up to know, all bonding in III–V/silicon tandem solar cells is based on planar silicon cells. Here, a transparent conductive adhesive (TCA) based on micron particle size is designed and implemented, which realizes the bonding of III–V cell and textured silicon cell for the first time. The TCA consists of epoxy adhesive 301 (Epoxy‐301) as transparent adhesive and silver‐coated flexible polymethylmethacrylate microspheres as conductive particles. The average contact resistance of TCA is 0.17 Ω cm2, and the transmittance exceeds 91% in the range of 800—1200 nm. In addition, TCA shows good stability in the etching process of GaAs substrates. Monolithic III–V/silicon device exhibits 25.1% power conversion efficiency (PCE) on thin and textured silicon heterojunction solar cells, which enables flexible properties of tandem cells. Compared with silicon subcell and III–V subcell, the performance of tandem device is improved by 28.3% and 8.6%, respectively. This strategy provides a broad research window for improving the performance of tandem solar cells based on industrialized textured‐silicon bottom cells.

Light addressable potentiometric sensor with well-ordered pyramidal pits-patterned silicon

Light addressable potentiometric sensor (LAPS) with the structure of electrolyte-insulator-semiconductor is a kind of field effect sensor that detects local potential changes caused by protonation and deprotonation between electrolyte and insulator by light pulse. And scanned light pulse allows two-dimensional imaging of the distribution of chemical/biological species on the surface of sensor. An important challenge is to achieve low-cost, strong anti-interference and high-performance silicon-based LAPS. In this study, we propose to combine microsphere lithography with wet etching to fabricate well-ordered, tunable and low-cost pyramidal pits-patterned silicon as semiconductor of LAPS. The morphology and optical properties of pyramidal pits-patterned silicon are tested and analyzed. The sensing characteristics and the pH imaging performance of LAPS are tested and evaluated. The experiment results and theoretical analyses show that LAPS with pyramidal pits-patterned silicon has acceptable pH response, good long-term stability, and high performance in terms of photocurrent enhancement ratio, signal-to-noise ratio and pH imaging. This work can provide a simple, low-cost, strong anti-interference and high-performance device for pH-related chemical/biological analysis.

Modeling pyramidal silicon nanopores with effective ion transport

While the electrical models of the membrane-based solid-state nanopores have been well established, silicon-based pyramidal nanopores cannot apply these models due to two distinctive features. One is its 35.3° half cone angle, which brings additional resistance to the moving ions inside the nanopore. The other is its rectangular entrance, which makes calculating the access conductance challenging. Here, we proposed and validated an effective transport model (ETM) for silicon-based pyramidal nanopores by introducing effective conductivity. The impact of half cone angle can be described equivalently using a reduced diffusion coefficient (effective diffusion coefficient). Because the decrease of diffusion coefficient results in a smaller conductivity, effective conductivity is used for the calculation of bulk conductance in ETM. In the classical model, intrinsic conductivity is used. We used the top-down fabrication method for generating the pyramidal silicon nanopores to test the proposed model. Compared with the large error (≥25% in most cases) when using the classical model, the error of ETM in predicting conductance is less than 15%. We also found that the ETM is applicable when the ratio of excess ion concentration and bulk ion concentration is smaller than 0.2. At last, it is proved that ETM can estimate the tip size of pyramidal silicon nanopore. We believe the ETM would provide an improved method for evaluating the pyramidal silicon nanopores.

Growth of Graphitic Carbon Nitride-Incorporated ZnO Nanorods on Silicon Pyramidal Substrates for Enhanced Hydrogen Sensing Applications

Monitoring the hydrogen gas (H2) level is highly important in a wide range of applications. Oxide-carbon hybrids have emerged as a promising material for the fabrication of gas sensors for this purpose. Here, for the first time, graphitic carbon nitride (g-C3N4)-doped zinc oxide nanorods (ZNRs) have been grown on silicon (Si) pyramid-shaped surfaces by the facile hydrothermal reaction method. The systematic material analyses have revealed that the g-C3N4 nanostructures (NS) have been consistently incorporated into the ZNRs on the pyramidal silicon (Py-Si) surface (g-C3N4-ZNRs/Py-Si). The combined properties of the present structure exhibit an excellent sensitivity (∼53%) under H2 gas exposure, better than that of bare ZNRs (12%). The results revealed that the fine incorporation of g-C3N4 into ZNRs on the Py-Si surface improves the H2 gas sensing properties when compared to that of the planar silicon (Pl-Si) surface. The doping of g-C3N4 into ZNRs increases the electrical conductivity through its graphene-like edges (due to the formation of delocalized bonds in g-C3N4 during carbon self-doping), as revealed by FESEM images. In addition, the presence of defects in g-C3N4 induces the gas adsorption properties of ZnO through its active sites. Moreover, the integration of the 1D structure (g-C3N4-ZNRs) into a 3D pyramidal structure opens up new opportunities for low-cost H2 gas sensing at room temperature. It is an easy way to enhance the gas sensing properties of ZNRs at room temperature, which is desirable for practical H2 sensor applications.

Rapid anisotropic chemical etching for quick formation of novel octagonal pyramids on silicon surface for photovoltaics

A novel octagonal micro pyramid structure was formed by etching a monocrystalline silicon wafer (100) by employing a wet chemical anisotropic etching process. The main objective is to reduce the silicon wafer's front surface reflectance, improve surface morphology, enhance wettability, and increase the coverage area of the octagonal pyramids on the surface of silicon wafers. The reaction time of the etching process was kept precise under strict observation and control. The experimental results demonstrate a significant reduction in silicon wafers' optical surface reflectance, achieving the lowest reflectance of 8.87%, along with improved surface morphology, periodicity, and coverage of more than 88%. While adding hydrofluoric acid together with magnetic stirring (mechanical agitation) at 300 rpm was advantageous in forming the octagonal silicon pyramid with a high etch rate of 0.41 um/min and significantly reducing the reaction time.

Correction to: Role of Au–Ag alloy plasmonic layer thickness over pyramidal silicon in controlling SERS activity

Correction to: Role of Au–Ag alloy plasmonic layer thickness over pyramidal silicon in controlling SERS activity