Investigation of c-Si surface passivation using thermal ALD deposited HfO2 films

Gougam, Adel; Rajab, Bilal; Afif, Abdulla Bin

doi:10.1016/j.mssp.2019.02.012

Cited by 22 publications

(27 citation statements)

References 30 publications

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“…[ 14,19 ] Differing charge polarities may be a consequence of the deposition conditions. Many reports on ALD‐grown HfO 2 involve thermal ALD, with positive fixed charges being observed using tetrakis(methylethylamide)hafnium and trimethylhafnium precursors, [ 13,31,33 ] and negative charges being reported with tetrakis(dimethylamido)hafnium, [ 14 ] trimethylhafnium, [ 19 ] and hafnium tetrachloride [ 34 ] precursors. HfO 2 deposited under our conditions has the same charge polarity as Al 2 O 3 , that is negatively charged.…”

Section: Resultsmentioning

confidence: 99%

Electronic Characteristics of Ultra‐Thin Passivation Layers for Silicon Photovoltaics

Pain

Khorani

Niewelt

et al. 2022

Adv Materials Inter

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on PERC technologies and get even closer to the theoretical single-junction efficiency limit, electrical losses in the contacted regions must be reduced. [3][4][5] Passivating contacts can help alleviate such losses by simultaneously suppressing the current of non-collected carriers to the contact, and by reducing recombination sites at the interface. Introducing a passivating interlayer between the metal/silicon interface provides a route to reducing the recombination current density, J 0 , [6,7] thereby increasing device voltage. [3] Passivating contacts have achieved some success to date, with the strongest candidates being polysilicon on top of thin silicon oxide layers (e.g., tunnel oxide passivating contacts (TOPCon) or poly silicon on oxide (POLO)) and amorphous silicon (a-Si) heterojunctions. [3,7,8] TOPCon is an efficient electron-selective contact but has a high thermal budget with temperatures around 900 °C needed to reduce the contact resistivity to acceptable levels. [9] An efficient hole-selective layer that can match or exceed the performance of the current electron-selective materials would be of considerable interest. The use of SiO 2 -based hole-selective contacts has so far failed to reach equivalent levels. [10,11] The most promising hole-selective contacting materials are p-type a-Si and siliconrich SiC, but conventional high-temperature Ag screen printing methods are not necessarily compatible with such contacts. [10] Surface passivating thin films are crucial for limiting the electrical losses during charge carrier collection in silicon photovoltaic devices. Certain dielectric coatings of more than 10 nm provide excellent surface passivation, and ultra-thin (<2 nm) dielectric layers can serve as interlayers in passivating contacts. Here, ultra-thin passivating films of SiO 2 , Al 2 O 3 , and HfO 2 are created via plasma-enhanced atomic layer deposition and annealing. It is found that thin negatively charged HfO 2 layers exhibit excellent passivation properties-exceeding those of SiO 2 and Al 2 O 3 -with 0.9 nm HfO 2 annealed at 450 °C providing a surface recombination velocity of 18.6 cm s −1 . The passivation quality is dependent on annealing temperature and layer thickness, and optimum passivation is achieved with HfO 2 layers annealed at 450 °C measured to be 2.2-3.3 nm thick which give surface recombination velocities ≤2.5 cm s −1 and J 0 values of ≈14 fA cm −2 . The superior passivation quality of HfO 2 nanolayers makes them a promising candidate for future passivating contacts in high-efficiency silicon solar cells.

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Section: Resultsmentioning

confidence: 99%

Electronic Characteristics of Ultra‐Thin Passivation Layers for Silicon Photovoltaics

Pain

Khorani

Niewelt

et al. 2022

Adv Materials Inter

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“…Surface passivation is of vital importance for achieving higher conversion efficiency of crystalline silicon solar cells. [1][2][3] In previous studies, many materials have been adopted for passivation layers, including hydrogenated amorphous silicon (a-Si:H), [4] silicon oxide (SiO x ), [5,6] silicon nitride (SiN x ), [7] aluminum oxide (Al 2 O 3 ), [8,9] hafnium oxide (HfO 2 ), [10] organic materials, [11] and so on. Among them, Al 2 O 3 exhibits excellent passivation capability due to the low interfacial defect density and a high density of negative fixed charges (Q f ¼ 10 12 to 10 13 cm À2 ) which are located very close to the Si/Al 2 O 3 interface.…”

Section: Introductionmentioning

confidence: 99%

Ultrathin Aluminum Oxide Films Induced by Rapid Thermal Annealing for Effective Silicon Surface Passivation

Wang

Liu

et al. 2021

Physica Rapid Research Ltrs

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A novel method of preparing ultrathin aluminum oxide films by rapid thermal annealing (RTA) treatment for effective silicon surface passivation is proposed. The high‐temperature RTA processing (750–825 °C) for tens of seconds in an oxygen atmosphere completely converts the thermally evaporated aluminum metal nanofilms (1–5 nm) on crystalline silicon to aluminum oxide (Al2O3) films, with a thin SiOx layer formed at the interface between the silicon and the Al2O3. The generated Al2O3 film can provide superior passivation quality for the silicon surface, even better than that obtained by the thermal atomic layer deposition technique. Moreover, the growth kinetics of the Al2O3 passivating film indicates that it is a diffusion‐controlled activation process, with an energy barrier of 3.3 eV for aluminum ions diffusing across the metal/oxide interface.

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“…At present, an alternative strategy, namely passivation, has been developed to treat AMD at the source by suppressing the oxidation of pyrite and other sulfide minerals. The passivation method mainly focuses on using chemical passivation materials to come in contact with pyrite, where its surface will combine via ionic or covalent bonds to form a dense passivation film, thereby inhibiting the oxidation of iron in the pyrite lattice. , So far, a large amount of passivation materials including phosphates, silicates, triethylenetetramines hydroxyquinonline, silicate, catechol, phosphate, triethylenetetramine, and phospholipids have been reported. − Nevertheless, each of these passivators has its own drawbacks. For example, the formation of a phosphate or silicate passivation film may involve hydrogen peroxide or hypochlorite, which is more expensive.…”

Section: Introductionmentioning

confidence: 99%

“…The passivation method mainly focuses on using chemical passivation materials to come in contact with pyrite, where its surface will combine via ionic or covalent bonds to form a dense passivation film, thereby inhibiting the oxidation of iron in the pyrite lattice. 17,18 So far, a large amount of passivation materials including phosphates, silicates, triethylenetetramines hydroxyquinonline, silicate, catechol, phosphate, triethylenetetramine, and phospholipids have been reported. 19−24 Nevertheless, each of these passivators has its own drawbacks.…”

Section: Introductionmentioning

confidence: 99%

Performance and Mechanisms of PropS-SH/HA Coatings in the Inhibition of Pyrite Oxidation

et al. 2021

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Acid mine drainage (AMD) entering the environment will cause long-term environmental pollution and ecological damage, the treatment or remediation for which has become a difficult worldwide problem. To control AMD at the source, a novel composite coating, hydroxyapatite (HA) as the filler embedded in a γ-mercaptopropyltrimethoxysilane (PropS-SH) coating, was introduced in this study. The performance and mechanisms of PropS-SH/HA coatings in the inhibition of pyrite oxidation were investigated by chemical leaching testing and material structure characterization. The results of the investigations revealed that the addition of an appropriate amount of HA can enhance the passivation efficiency of the PropS-SH coating. The best coating was obtained from 3% (v/v) of PropS-SH solution with 16 wt % HA, as this coating decreased pyrite oxidation by 78.7% (based on total Fe release). The main mechanism of PropS-SH/HA for the inhibition of pyrite oxidation involved the generation of a PropS-SH network through a polycondensation reaction. The addition of HA increased the stability of the passivation film composed of PropS-SH as well as the combining capacity of PropS-SH/HA through the formation of Si–O–Si and Fe–O–Si bonds, respectively.

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Investigation of c-Si surface passivation using thermal ALD deposited HfO2 films

Cited by 22 publications

References 30 publications

Electronic Characteristics of Ultra‐Thin Passivation Layers for Silicon Photovoltaics

Electronic Characteristics of Ultra‐Thin Passivation Layers for Silicon Photovoltaics

Ultrathin Aluminum Oxide Films Induced by Rapid Thermal Annealing for Effective Silicon Surface Passivation

Performance and Mechanisms of PropS-SH/HA Coatings in the Inhibition of Pyrite Oxidation

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