Self-assembled multifunctional nanostructures for surface passivation and photon management in silicon photovoltaics

Abstract This work reports the fabrication and characterization of multifunctional, nanostructured passivation layers formed using a self-assembly process that provide both surface passivation and improved light trapping in crystalline silicon photovoltaic (PV) cells. Scalable block copolymer self-assembly and vapor phase infiltration processes are used to form arrays of aluminum oxide nanostructures (Al2O3) on crystalline silicon without substrate etching. The Al2O3 nanostructures are characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM), and spectroscopic ellipsometry. Injection-level dependent photoconductance measurements are used to determine the effective carrier lifetime of the samples to confirm the nanostructures successfully passivate the Si surface. Finite element method simulations and reflectance measurement show that the nanostructures increase the internal rear reflectance of the PV cell by suppressing the parasitic optical losses in the metal contact. An optimized morphology of the structures is identified for their potential use in PV cells as multifunctional materials providing surface passivation, photon management, and carrier transport pathways.

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Transmission Electron Microscopy Studies of Electron-Selective Titanium Oxide Contacts in Silicon Solar Cells

Microscopy and Microanalysis ◽

10.1017/s1431927617012417 ◽

2017 ◽

Vol 23 (5) ◽

pp. 900-904 ◽

Cited By ~ 14

Author(s):

Haider Ali ◽

Xinbo Yang ◽

Klaus Weber ◽

Winston V. Schoenfeld ◽

Kristopher O. Davis

Keyword(s):

Electron Microscopy ◽

Transmission Electron Microscopy ◽

Solar Cells ◽

Titanium Oxide ◽

Surface Passivation ◽

Crystalline Silicon ◽

Silicon Solar Cells ◽

Crystalline Silicon Solar Cells ◽

Transmission Electron ◽

Low Efficiency

AbstractIn this study, the cross-section of electron-selective titanium oxide (TiO2) contacts for n-type crystalline silicon solar cells were investigated by transmission electron microscopy. It was revealed that the excellent cell efficiency of 21.6% obtained on n-type cells, featuring SiO2/TiO2/Al rear contacts and after forming gas annealing (FGA) at 350°C, is due to strong surface passivation of SiO2/TiO2 stack as well as low contact resistivity at the Si/SiO2/TiO2 heterojunction. This can be attributed to the transformation of amorphous TiO2 to a conducting TiO2−x phase. Conversely, the low efficiency (9.8%) obtained on cells featuring an a-Si:H/TiO2/Al rear contact is due to severe degradation of passivation of the a-Si:H upon FGA.

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Directive Effect of Chain Length in Modulating Peptide Nano-assemblies

Protein and Peptide Letters ◽

10.2174/0929866527666200224114627 ◽

2020 ◽

Vol 27 (9) ◽

pp. 923-929

Author(s):

Gaurav Pandey ◽

Prem Prakash Das ◽

Vibin Ramakrishnan

Keyword(s):

Electron Microscopy ◽

Amino Acids ◽

Light Scattering ◽

Chain Length ◽

Self Assembly ◽

The Self ◽

Ionic Charge ◽

Self Assembling ◽

Biophysical Techniques

Background: RADA-4 (Ac-RADARADARADARADA-NH2) is the most extensively studied and marketed self-assembling peptide, forming hydrogel, used to create defined threedimensional microenvironments for cell culture applications. Objectives: In this work, we use various biophysical techniques to investigate the length dependency of RADA aggregation and assembly. Methods: We synthesized a series of RADA-N peptides, N ranging from 1 to 4, resulting in four peptides having 4, 8, 12, and 16 amino acids in their sequence. Through a combination of various biophysical methods including thioflavin T fluorescence assay, static right angle light scattering assay, Dynamic Light Scattering (DLS), electron microscopy, CD, and IR spectroscopy, we have examined the role of chain-length on the self-assembly of RADA peptide. Results: Our observations show that the aggregation of ionic, charge-complementary RADA motifcontaining peptides is length-dependent, with N less than 3 are not forming spontaneous selfassemblies. Conclusion: The six biophysical experiments discussed in this paper validate the significance of chain-length on the epitaxial growth of RADA peptide self-assembly.

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Surface Passivation Studies of n-type Crystalline Silicon for HIT Solar Cells

Transactions on Electrical and Electronic Materials ◽

10.1007/s42341-021-00316-1 ◽

2021 ◽

Author(s):

M. Nagesh ◽

R. Suresh ◽

R. Jayapal ◽

K. N. Subramanya

Keyword(s):

Solar Cells ◽

Surface Passivation ◽

Crystalline Silicon

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Alpha helical surfactant-like peptides self-assemble into pH-dependent nanostructures

Soft Matter ◽

10.1039/d0sm02095h ◽

2021 ◽

Vol 17 (11) ◽

pp. 3096-3104

Author(s):

Valeria Castelletto ◽

Jani Seitsonen ◽

Janne Ruokolainen ◽

Ian W. Hamley

Keyword(s):

Electron Microscopy ◽

Transmission Electron Microscopy ◽

Small Angle ◽

Self Assembly ◽

X Ray ◽

Cryogenic Transmission Electron Microscopy ◽

X Ray Scattering ◽

Transmission Electron ◽

Ph Dependent ◽

Ray Scattering

A designed surfactant-like peptide is shown, using a combination of cryogenic-transmission electron microscopy and small-angle X-ray scattering, to have remarkable pH-dependent self-assembly properties.

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Leaching of Chalcopyrite under Bacteria–Mineral Contact/Noncontact Leaching Model

Minerals ◽

10.3390/min11030230 ◽

2021 ◽

Vol 11 (3) ◽

pp. 230

Author(s):

Pengcheng Ma ◽

Hongying Yang ◽

Zuochun Luan ◽

Qifei Sun ◽

Auwalu Ali ◽

...

Keyword(s):

Electron Microscopy ◽

Surface Passivation ◽

X Ray Diffraction ◽

X Ray ◽

Leaching Process ◽

Copper Leaching ◽

Hydrolysis Of ◽

Leaching Efficiency ◽

Leaching Models ◽

Scanning Electron

Bacteria–mineral contact and noncontact leaching models coexist in the bioleaching process. In the present paper, dialysis bags were used to study the bioleaching process by separating the bacteria from the mineral, and the reasons for chalcopyrite surface passivation were discussed. The results show that the copper leaching efficiency of the bacteria–mineral contact model was higher than that of the bacteria–mineral noncontact model. Scanning electron microscopy (SEM), X-ray diffraction (XRD), and Fourier-transform infrared (FTIR) were used to discover that the leaching process led to the formation of a sulfur film to inhibit the diffusion of reactive ions. In addition, the deposited jarosite on chalcopyrite surface was crystallized by the hydrolysis of the excess Fe3+ ions. The depositions passivated the chalcopyrite leaching process. The crystallized jarosite in the bacteria EPS layer belonged to bacteria–mineral contact leaching system, while that in the sulfur films belonged to the bacteria–mineral noncontact system.

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COMBINED EFFECT OF MECHANICAL GROOVING AND STAIN-ETCHED SURFACE ON OPTICAL AND ELECTRICAL PROPERTIES OF CRYSTALLINE SILICON SUBSTRATES

Surface Review and Letters ◽

10.1142/s0218625x14500413 ◽

2014 ◽

Vol 21 (03) ◽

pp. 1450041 ◽

Cited By ~ 10

Author(s):

AHMED ZARROUG ◽

LOTFI DERBALI ◽

RACHID OUERTANI ◽

WISSEM DIMASSI ◽

HATEM EZZAOUIA

Keyword(s):

Crystalline Silicon ◽

Light Trapping ◽

Front Surface ◽

Minority Carrier Lifetime ◽

Combined Effect ◽

Machining Process ◽

Silicon Substrates ◽

Textured Surface ◽

Crystalline Silicon Solar Cell ◽

Simple Method

This paper investigates the combined effect of mechanical grooving and porous silicon (PS) on the front surface reflectance and the electronic properties of crystalline silicon substrates. Mechanical surface texturization leads to reduce the cell reflectance, enhance the light trapping and augment the carrier collection probability. PS was introduced as an efficient antireflective coating (ARC) onto the front surface of crystalline silicon solar cell. Micro-periodic V-shaped grooves were made by means of a micro-groove machining process prior to junction formation. Subsequently, wafers were subjected to an isotropic potassium hydroxide ( KOH ) etching so that the V-shape would be turned to a U-shape. We found that the successive treatment of silicon surfaces with stain-etching, grooving then alkaline etching enhances the absorption of the textured surface, and decreases the reflectance from 35% to 7% in the 300–1200 nm wavelength range. We obtained a significant increase in the overall light path that generates the building up of the light trapping inside the substrate. We found an improvement in the illuminated I–V characteristics and an increase in the minority carrier lifetime τeff. Such a simple method was adopted to effectively reinforce the overall device performance of crystalline silicon-based solar cells.

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