Article
Materials Science, Multidisciplinary
Yu Zhang, Torn Veeken, Shaozhou Wang, Giuseppe Scardera, Malcolm Abbott, David Payne, Albert Polman, Bram Hoex
Summary: This study compares the 3D models of challenging black silicon textures obtained by atomic force microscopy (AFM) and plasma focused ion beam (PFIB) tomography techniques. The results provide strong evidence that PFIB tomography is a better choice for characterizing highly roughened surfaces such as black silicon, providing models with better reliability and consistency.
ADVANCED MATERIALS TECHNOLOGIES
(2022)
Article
Chemistry, Multidisciplinary
Matthew Eliceiri, Costas P. Grigoropoulos
Summary: In this study, we have improved the maximum two-dimensional translation rate of optically tweezed silicon nanowires using a silicon film substrate and a specific laser wavelength. We have also reduced the power usage significantly. The mechanism for the enhanced tweezing effect was explained using finite difference time domain simulation, and the robust and deterministic placement of the nanowires on the film surface was demonstrated experimentally.
Article
Nanoscience & Nanotechnology
Pengfei Cheng, Honglei Wang, Bjoern Mueller, Jens Mueller, Dong Wang, Peter Schaaf
Summary: Research has focused on efficiently harvesting solar energy with black silicon (b-Si), where highly conductive b-Si prepared by reactive ion etching can absorb a wide range of wavelengths and convert solar energy into electric power. The optimized b-Si shows low reflection rates and great potential for photothermal applications.
ACS APPLIED MATERIALS & INTERFACES
(2021)
Article
Optics
Xiwen Zhang, Sajeev John
Summary: The study addresses the issue of insufficient photogeneration in the visible range for wide-band photocatalysts like TiO2 and proposes enhancing photocatalytic efficiency through photonic crystal structures. By optimizing different photocatalyst structures, it was found that slanted conical-pore (scPore) showed the best visible light harvesting capability for weakly absorbing TiO2 when the photonic crystal thickness is fixed.
Article
Optics
Bingfei Dou, Rui Jia, Zhao Xing, Xiaojiang Yao, Dongping Xiao, Zhi Jin, Xinyu Liu
Summary: In this study, silicon nanostructures were synthesized via silver-catalyzed etching to improve the performance of solar cells, with atomic-layer-deposited Al2O3 passivation. The nanotextured cells achieved a lower surface recombination velocity, higher open-circuit voltage, and short-circuit current. Furthermore, the electrode contact property was enhanced by light-induced plating, leading to a best efficiency of 13.3% for the nano-textured cells, higher than the planar cell's 12%.
Article
Chemistry, Physical
Jianming Ding, Shuai Zou, Leilei Shen, Jonghyung Choi, Junhu Cui, Dichun Yuan, Chengkun Wu, Zheng Lu, Yulian Zeng, Ronglei Fan, Yadong Xu, Baochen Liao, Mingrong Shen, Xiaodong Su
Summary: This paper studied the influence of rear pyramid morphologies with different slope angles on the optical and electrical properties of bi-PERC solar cells. The results showed that a smoother rear surface was favorable for rear passivation but unfavorable for rear-side light trapping. Rear surface morphologies also influenced the front-side light trapping. The highest front-side average efficiency of 22.86% was achieved using a modified acidic polishing process.
ACS APPLIED ENERGY MATERIALS
(2022)
Article
Chemistry, Multidisciplinary
Jing Li, Bintong Huang, Yuanhao Wang, Aijia Li, Yong Wang, Yangyang Pan, Jia Chai, Ze Liu, Yueming Zhai
Summary: The single-molecule technique for investigating unlabeled proteins in solution is challenging, but nanopore sensing offers a label-free tool for collecting structural information. This study developed a reliable method to convert a silicon nitride nanopore into a stable nanonet platform for single-entity sensing. The nanonet provides more structural information and captures the UV-light-induced structural-change process of individual proteins.
ADVANCED MATERIALS
(2023)
Review
Biophysics
Ilias Georgakopoulos-Soares, Emmanouil L. Papazoglou, Panagiotis Karmiris-Obratanski, Nikolaos E. Karkalos, Angelos P. Markopoulos
Summary: This article discusses the correlation between surface roughness and antibacterial properties. It introduces the concepts of surface roughness and texture, and describes the impact of different machining and treatment methods on antibacterial properties. It provides a thorough analysis of bacterial adhesion and growth, and comprehensively reviews the most recent studies in this research area. The authors aim to assist and promote further research by providing a systematic review of recent advances.
COLLOIDS AND SURFACES B-BIOINTERFACES
(2023)
Article
Materials Science, Multidisciplinary
Haoliang Sun, Xinxin Lian, Yuanjiang Lv, Guangxin Wang
Summary: Black Ag-Mo alloy films were spontaneously formed on silver sheets by composite target sputtering, exhibiting strong light trapping effect in the visible wavelength range and reducing the reflectivity substantially. The conical particle arrays on the Ag-Mo alloy films are responsible for the light trapping properties, providing a new idea for fabrication of high light trapping materials.
OPTICAL MATERIALS EXPRESS
(2021)
Article
Optics
Benedikt Blaesi, Mario Hanser, Klaus Jaeger, Oliver Hoehn
Summary: Solar cells can enhance light trapping efficiency by utilizing gratings. We present an analytical model to optimize the grating period and provide guidelines for maximizing light trapping in high-end solar cells.
Article
Optics
Long Liang, Wenwen Liu, Yu Cao, Dehua Zhu, Jian Zhang, Yanling Yu
Summary: In this study, a novel composite total internal reflectance fiber structure constructed on monocrystalline silicon with specific micro-structures and closely nested PMMA film is proposed for the first time. It achieves a more effective sunlight trap and anti-reflection effect. Experimental results show that the reflectivity of the composite structure significantly decreases in the wavelength range of 350-1000 nm, providing a new approach for designing and fabricating silicon surfaces with ultra-low reflectivity.
OPTICS AND LASER TECHNOLOGY
(2022)
Article
Chemistry, Physical
L. Liu, F. Lu, J. Tian, X. Zhangyang
Summary: The optical performance of heterojunction AlGaN nanowire arrays can be significantly improved by decorating them with metal nanoparticles. Optimizing the Al components and NPs size and spacing can enhance the optical properties. The adsorption of Al NPs can increase light absorption, while the adsorption of metal particles can improve light binding capacity.
MATERIALS TODAY ENERGY
(2021)
Article
Chemistry, Multidisciplinary
Jie Mao, Bingchang Zhang, Yihao Shi, Xiaofeng Wu, Yuanyuan He, Di Wu, Jiansheng Jie, Chun-Sing Lee, Xiaohong Zhang
Summary: This study presents a high-sensitivity photodetector based on a conformal MoS2/silicon nanowire array heterojunction with an ultrathin Al2O3 interfacial passivation layer, which can exhibit broadband photoresponse ranging from 300 to 1600 nm and detect ultra-weak infrared signals effectively. The device is capable of detecting ultra-weak IR signals without applying any external bias, showing great potential for low-cost and high-performance optoelectronic devices.
ADVANCED FUNCTIONAL MATERIALS
(2022)
Article
Multidisciplinary Sciences
Changyeong Jeong, Yong-Bum Park, L. Jay Guo
Summary: The introduction of an ultrathin silver film as a transparent electrode helps eliminate waveguide mode in OLEDs and enhances external quantum efficiency. By designing an OLED structure below the cutoff thickness of waveguide mode, waveguide mode can be effectively eliminated, promoting cost-effective high-efficiency OLEDs.
Review
Chemistry, Multidisciplinary
Jimmy Soueiti, Rim Sarieddine, Hind Kadiri, Akram Alhussein, Gilles Lerondel, Roland Habchi
Summary: Since the discovery of black silicon, scientists worldwide have been exploring various methods to utilize this super material in different industries due to its low reflectivity and excellent electronic and optoelectronic properties. This review presents common fabrication methods of black silicon, including metal-assisted chemical etching, reactive ion etching, and femto-second laser irradiation. It assesses different nanostructured silicon surfaces based on their reflectivity and applicable properties in both visible and infrared ranges. The review also discusses the most cost-efficient technique for mass production of black silicon and potential alternative materials to replace silicon. Furthermore, it investigates the applications of black silicon in solar cells, IR photo-detectors, and antibacterial purposes, along with the challenges faced.
Article
Optics
Behrad Radfar, Kexun Chen, Olli E. Setala, Ville Vahanissi, Hele Savin, Xiaolong Liu
Summary: In this study, we investigate the surface morphology, optical absorption (400-1100 nm), and carrier lifetime of black silicon fabricated by femtosecond (fs) laser in air. We explore a wide range of cumulative fluence delivered to the sample, represented by a single parameter xi. We also examine the laser-oxidized surface layer and its impact on the mentioned properties through photoluminescence spectra measurements.
Article
Materials Science, Multidisciplinary
Hanchen Liu, Toni P. Pasanen, Tsun Hang Fung, Joonas Isometsa, Oskari Leiviska, Ville Vahanissi, Hele Savin
Summary: Silicon nitride (SiNx)-based passivation schemes show promising potential for Ge surfaces, with a higher negative charge density compared to Si samples. The post-deposition anneal process significantly reduces the surface recombination velocity in both Si and Ge samples. The addition of an atomic-layer-deposited aluminum oxide (Al2O3) layer on SiNx-coated samples effectively reduces the midgap interface defect density (D-it), while neutralizing the charge density on Ge samples.
PHYSICA STATUS SOLIDI A-APPLICATIONS AND MATERIALS SCIENCE
(2023)
Article
Physics, Applied
Hanchen Liu, Toni P. Pasanen, Oskari Leiviska, Joonas Isometsa, Tsun Hang Fung, Marko Yli-Koski, Mikko Miettinen, Pekka Laukkanen, Ville Vahanissi, Hele Savin
Summary: The excellent field-effect passivation provided by aluminum oxide (Al2O3) on germanium surfaces relies on a high negative fixed charge. However, this study investigates the surface passivation performance and charge polarity of plasma-enhanced atomic layer deposited (PEALD) silicon oxide (SiO2) on Ge. The results show that even a 3 nm thick PEALD SiO2 provides a positive charge density and a relatively good surface passivation. Furthermore, adding an ALD Al2O3 layer further improves the surface passivation.
APPLIED PHYSICS LETTERS
(2023)
Article
Engineering, Electrical & Electronic
Kexun Chen, Olli E. Setala, Xiaolong Liu, Behrad Radfar, Toni P. Pasanen, Michael D. Serue, Juha Heinonen, Hele Savin, Ville Vahanissi
Summary: Metal-assisted chemical etched (MACE) nanostructures are widely used in the solar cell industry due to their excellent optical properties and cost-efficient fabrication process. However, the photodetection community has not shown much interest in MACE due to its drawbacks. This study demonstrates the fabrication of high-performance MACE p-n photodiodes with above 90% external quantum efficiency (EQE) and low dark current using industrially applicable methods, showcasing the potential of MACE nanostructures in low-cost photodiode fabrication.
IEEE SENSORS JOURNAL
(2023)
Article
Chemistry, Physical
Shengyang Li, Hussein M. Ayedh, Marko Yli-Koski, Ville Vahanissi, Hele Savin, Jani Oksanen
Summary: In this study, n-and p-type Si photoconductors covered with silver nanoparticles were designed to demonstrate their sensitivity to the metal-assisted chemical etching (MACE) process and their ability to provide in situ information about the reaction dynamics. Experimental results showed a stronger response of both n-and p-type photoconductors to MACE compared to light intensity of 2 mW/cm2. A thermodynamic analysis of the energy levels explained the observations, highlighting the contribution of electron and hole injection from the Si/etching solution interface to the response and excitation of the photoconductors. These findings demonstrate a new chemical operating mode for photoconductors, enabling in situ monitoring of reaction dynamics and chemical sensing.
JOURNAL OF PHYSICAL CHEMISTRY C
(2023)
Article
Nanoscience & Nanotechnology
Tsun Hang Fung, Joonas Isometsa, Juha-Pekka Lehtio, Toni P. Pasanen, Hanchen Liu, Oskari Leiviska, Pekka Laukkanen, Hele Savin, Ville Vahanissi
Summary: Nanostructured germanium surfaces have achieved >99% absorption in a wide wavelength range, promising high performance for optoelectronic devices. By characterizing the surface and interface properties, we identified the limiting factors for surface recombination velocity of the nanostructures and developed a surface passivation scheme using atomic-layer-deposited aluminum oxide and sequential chemical treatment. With this scheme, we achieved a low surface recombination velocity and 1% reflectance from ultraviolet to near-infrared. We discussed the impact of these results on Ge-based optoelectronic applications.
Article
Optics
Andreas Wessels, Leonard Christen, Adrian Callies, Thomas Kroyer, Oliver Hoehn, Benedikt Blaesi
Summary: This paper compares two model approaches for describing the optical properties of PV modules with a colored interference layer system. One approach is based on a microfacet-based bidirectional scattering distribution function (BSDF) model, and the other is based on ray tracing. The results show that the microfacet-based BSDF model is sufficient for the structures used in the MorphoColor application. Structure inversion has a significant influence only for extreme angles and very steep structures.
Article
Chemistry, Multidisciplinary
M. Garin, T. P. Pasanen, G. Lopez, V. Vahanissi, K. Chen, I. Martin, H. Savin
Summary: Reducing substrate thickness to cut costs is a common practice in the crystalline silicon photovoltaic industry. However, maintaining high absorption in thin wafers is a challenge. By using black-Si nanotexture on thin uncommitted wafers, ideal light trapping is achieved with wafer thicknesses as low as 40, 20, and 10 μm when paired with a back reflector. Implementing this technology in solar cells led to a 43% improvement in output power compared to reference cells.
Article
Materials Science, Coatings & Films
Nupur Bihari, Ismo T. S. Rauha, Giovanni Marin, Craig Ekstrum, Chathura de Alwis, Pierce J. Mayville, Hele Savin, Maarit Karppinen, Joshua M. Pearce
Summary: The potential of 3-D printing polymers in low-weight space flight hardware and vacuum equipment has attracted increasing interest. However, the formation mechanisms of atomic layer deposition (ALD) coatings on 3-D printed polymers are not well understood, limiting their use in vacuum environments. This study investigates the film formation mechanisms of ALD alumina on porous 3-D printed polymers, revealing that substrate porosity and polymer functionality play a dominant role in film formation behavior.
SURFACE & COATINGS TECHNOLOGY
(2023)
Article
Nanoscience & Nanotechnology
Olli E. Seta''la'', Kexun Chen, Toni P. Pasanen, Xiaolong Liu, Behrad Radfar, Ville Va''ha''nissi, Hele Savin
Summary: By combining a nanostructured surface with an optimized implanted junction, we have addressed the issues of reflectance losses and junction recombination in detecting UV light using Si photodiodes. The performance of our design has been compared to state-of-the-art commercial counterparts, and we have achieved a significant improvement in responsivity over a wide wavelength range. The detector design presented maintains simplicity in fabrication while meeting the important figures of merit relevant to photodiodes.
Article
Crystallography
Joonas Isometsa, Zahra Jahanshah Rad, Tsun H. Fung, Hanchen Liu, Juha-Pekka Lehtio, Toni P. Pasanen, Oskari Leiviska, Mikko Miettinen, Pekka Laukkanen, Kalevi Kokko, Hele Savin, Ville Vahanissi
Summary: Germanium is a promising material for applications like field effect transistors and radiation detectors/solar cells. However, efficient passivation of germanium surfaces is challenging. The combination of HF and DIW surface cleaning with ALD Al2O3 results in a compromised quality Ge suboxide interlayer (GeOx, x < 2). By using a low-temperature heating and a controlled oxidation in a ultrahigh vacuum (LT-UHV) treatment, the composition and crystallinity of the oxide layer can be improved, leading to a reduction in interface defect density (D-it) and achieving low SRV values.
Article
Materials Science, Multidisciplinary
Iris Mack, Kawa Rosta, Ulviyya Quliyeva, Jennifer Ott, Toni P. Pasanen, Ville Vahanissi, Zahra Sadat Jahanshah Rad, Juha-Pekka Lehtio, Pekka Laukkanen, Caterina Soldano, Hele Savin
Summary: The quality of the oxide-semiconductor interface has a direct impact on device electrical properties and performance. Traditional characterization methods may also affect the interface. This study investigates the impact of different deposition methods on the Al2O3/Si interface, revealing that magnetron sputtering induces significant damage and a high density of positive charges, while thermal evaporation has a modest impact. Annealing repairs the damage but also affects the film's charge.
PHYSICA STATUS SOLIDI A-APPLICATIONS AND MATERIALS SCIENCE
(2023)
Article
Chemistry, Multidisciplinary
Olli E. E. Setala, Martin J. J. Prest, Konstantin D. D. Stefanov, Douglas Jordan, Matthew R. R. Soman, Ville Vahanissi, Hele Savin
Summary: By replacing traditional methods with surface nanoengineering, the performance of commercial backside illuminated CMOS image sensors can be significantly improved in terms of spectral range, photosensitivity, and dark current reduction.
Article
Chemistry, Physical
Vladyslav Matkivskyi, Oskari Leiviska, Sigurd Wenner, Hanchen Liu, Ville Vahanissi, Hele Savin, Marisa Di Sabatino, Gabriella Tranell
Summary: This study investigated the application of two widely used atomic layer deposition precursors, TDMA-Ti and TiCl4, in TiOx-based thin films as a passivating contact material for solar cells. It was found that both precursors are suitable for similar deposition temperatures (150 °C). Post-deposition annealing significantly improved the passivation properties of the TiOx film, increasing the minority carrier lifetime (tau(eff)) by over 200 μs.AlOy/TiOx stack reduced the sheet resistance by 40% compared to pure TiOx. The passivation quality of the (AlOy/TiOx) stack was found to depend on the precursor and the ratio of AlOy to TiOx deposition cycles.
Article
Chemistry, Multidisciplinary
Maciej Krajewski, Adrian Callies, Minasadat Heydarian, Maryamsadat Heydarian, Mario Hanser, P. S. C. Schulze, Benedikt Blaesi, Oliver Hoehn
Summary: The proper light management strategy is crucial for achieving high power conversion efficiency in perovskite solar cell devices. Texturization of the front surface, similar to established solar cell technologies, can help reduce reflection losses. In this study, a honeycomb-like textured SU-8 photoresist layer is applied to a planar perovskite solar cell using a roller nanoimprint technique, resulting in a significant reduction in solar-weighted reflectance and an increase in current density. The findings can also be applied to perovskite-silicon tandem solar cells, providing a promising pathway for reflection reduction in future devices.
ADVANCED MATERIALS INTERFACES
(2023)
