Controlling Light- and Elevated-Temperature-Induced Degradation With Thin Film Barrier Layers

Varshney, Utkarshaa; Chan, Catherine; Hoex, Bram; Hallam, Brett; Hamer, Phillip; Ciesla, Alison; Chen, Daniel; Liu, Shaoyang; Sen, Chandany; Samadi, Aref; Abbott, Malcolm

doi:10.1109/jphotov.2019.2945199

Cited by 27 publications

(16 citation statements)

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“…Note that this would also be consistent with recent reports by other groups. [16,28] In conclusion, the total hydrogen concentration diffused into crystalline silicon from hydrogen-rich SiN x :H layers during RTA has been measured as a function of RTA peak temperature, layers were found to be necessary at higher RTA peak temperatures for preventing hydrogen from diffusing into the silicon bulk. For example, to reduce [H tot ] by a factor of 4 at ϑ peak ¼ 800 C, a 20 nm thick Al 2 O 3 layer was required.…”

mentioning

confidence: 88%

“…The adaption of such diffusion barriers could be useful in the production of silicon solar cells, where hydrogen in‐diffusion into the silicon bulk has recently been identified as one major reason for detrimental light‐induced degradation effects. [ 16,27,28 ]…”

Section: Figurementioning

confidence: 99%

“…The adaption of such diffusion barriers could be useful in the production of silicon solar cells, where hydrogen in-diffusion into the silicon bulk has recently been identified as one major reason for detrimental light-induced degradation effects. [16,27,28] Experimental Section Sample Preparation: We used (100)-oriented 300 μm thick 1.4 Ω cm boron-doped Fz-Si wafers. The 6 00 Fz-Si wafers were first cleaned with a surface-active agent.…”

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confidence: 99%

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Atomic‐Layer‐Deposited Al₂O₃ as Effective Barrier against the Diffusion of Hydrogen from SiN_x:H Layers into Crystalline Silicon during Rapid Thermal Annealing

Helmich

Walter

Bredemeier

et al. 2020

Physica Rapid Research Ltrs

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Atomic-layer-deposited (ALD) Al 2 O 3 films with a thickness of a few nanometers have been successfully applied in microelectronics and photovoltaics. [1-5] In particular, in silicon-based solar cells, the introduction of Al 2 O 3 surface passivation layers was a crucial step towards higher efficiencies of industrial solar cells in recent years. The metal contacts in today's industrial silicon solar cells are made by screen-printing of metal pastes in combination with a subsequent rapid thermal annealing (RTA) step at set-peak temperatures in the range between 750 and 850 C for a few seconds. [6] To preserve the excellent passivation quality of the ALD-Al 2 O 3 layers on the silicon surface during the RTA step, the Al 2 O 3 layers are capped by silicon nitride (SiN x) layers. These top layers are grown by means of plasmaenhanced chemical vapor deposition (PECVD), resulting in amorphous SiN x :H layer with very high hydrogen content (typically in the range of 10-20 at%). [7] In contrast, ALD-Al 2 O 3 layers have a hydrogen content in the range of only 1-2 at%. [3] During the RTA step, hydrogen partly diffuses from the hydrogen-rich SiN x layer [8] through the Al 2 O 3 layer to the interface and also into the crystalline silicon bulk, where it is able to passivate defects. [9-11] Interestingly, the hydrogen was also found to be able to create new recombination centers in the silicon bulk, in some cases leading to a severe degradation in solar cell efficiency during illumination. [12-16] Therefore, in photovoltaics, the control of the amount of hydrogen diffusing into the crystalline silicon bulk has turned out to be of utmost importance. There have been conjectures in the literature that Al 2 O 3 layers might severely hamper the in-diffusion of hydrogen from SiN x :H into the silicon bulk. [17,18] However, these studies did not provide any quantitative measurements on how effective Al 2 O 3 actually is as a hydrogen barrier. This letter aims at closing this gap by quantifying the amount of hydrogen diffused into the silicon bulk through Al 2 O 3 layers of different thicknesses (5À25 nm) at varying RTA peak temperatures ϑ peak. Figure 1 shows exemplary measurements for three group A samples (see Experimental Section) with SiN x :H films of different compositions, fired at a measured RTA peak temperature of (792 AE 10) C. Directly after RTA, the hydrogen is mainly present in the form of hydrogen dimers H 2 in the silicon bulk. [19] These H 2 dimers dissociate during low-temperature annealing in darkness (e.g., at 160 C) and the hydrogen atoms subsequently passivate boron dopant atoms. [20] As a consequence, the bulk resistivity ρ of the sample increases as a function of time during dark annealing at 160 C on a hotplate. We measure the resistivities in-between the periods of 160 C-dark annealing using

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Section: Figurementioning

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Atomic‐Layer‐Deposited Al₂O₃ as Effective Barrier against the Diffusion of Hydrogen from SiN_x:H Layers into Crystalline Silicon during Rapid Thermal Annealing

Helmich

Walter

Bredemeier

et al. 2020

Physica Rapid Research Ltrs

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“…Therefore, they suggested that hydrogen might play a role on the formation of LeTID. Moreover, Nakayashiki et al, 83 Morishige et al, 84 Bredemeier et al, 17 Jensen et al, 21 Varshney et al, 85 and Chan et al 81 all hypothesized that hydrogen played a key role on the formation of LeTID. On the other hand, other researchers pointed out that metallic impurity might be a candidate on the formation of LeTID.…”

Section: Lid In Cast Mono‐like Silicon and Ways To Suppress Itmentioning

confidence: 99%

“…The methods to suppress LeTID have been intensely studied. So far, lower peak firing temperature, 84 modification of firing profile (slower cooling rate), 19 thin‐film barrier layer, 85 controlling starting material quality, 86,88 accelerated degradation and regeneration, 84 and design of high‐temperature steps to alter impurity distributions 20,89 have been reported to suppress LeTID effectively. Nevertheless, the advantages and disadvantages of these methods should be discussed.…”

Section: Lid In Cast Mono‐like Silicon and Ways To Suppress Itmentioning

confidence: 99%

Defect engineering in cast mono‐like silicon: A review

Song

2020

Progress in Photovoltaics

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Cast mono‐like silicon is a promising material for next‐generation silicon solar cells with higher efficiency and lower cost compared with currently commercialized silicon solar cells. So far, cast mono‐like silicon technique still faces several problems, including multicrystallization, dislocation clusters, sub‐grain boundaries, and impurity contamination, which hinder its mass‐scale applications in photovoltaic industry. In this review, we will introduce these common problems in turn and discuss a multitude of the reported studies on eliminating these problems. Furthermore, light and elevated temperature‐induced degradation (LeTID) was recently reported to be a severe problem of cast mono‐like silicon solar cells, which can cause power loss over 10% relative. This review will introduce the behaviors and the proposed mechanisms of LeTID as well as the methods to suppress LeTID in Section 4. In the subsequent section, the efficiency potential and distribution of cast mono‐like silicon solar cells are discussed. At last, a comprehensive summary will be given for this review.

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Hydrogenation

Ciesla

2024

Photovoltaic Solar Energy

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Controlling Light- and Elevated-Temperature-Induced Degradation With Thin Film Barrier Layers

Cited by 27 publications

References 50 publications

Atomic‐Layer‐Deposited Al₂O₃ as Effective Barrier against the Diffusion of Hydrogen from SiN_x:H Layers into Crystalline Silicon during Rapid Thermal Annealing

Atomic‐Layer‐Deposited Al₂O₃ as Effective Barrier against the Diffusion of Hydrogen from SiN_x:H Layers into Crystalline Silicon during Rapid Thermal Annealing

Defect engineering in cast mono‐like silicon: A review

Hydrogenation

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Controlling Light- and Elevated-Temperature-Induced Degradation With Thin Film Barrier Layers

Cited by 27 publications

References 50 publications

Atomic‐Layer‐Deposited Al2O3 as Effective Barrier against the Diffusion of Hydrogen from SiNx:H Layers into Crystalline Silicon during Rapid Thermal Annealing

Atomic‐Layer‐Deposited Al2O3 as Effective Barrier against the Diffusion of Hydrogen from SiNx:H Layers into Crystalline Silicon during Rapid Thermal Annealing

Defect engineering in cast mono‐like silicon: A review

Hydrogenation

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Atomic‐Layer‐Deposited Al₂O₃ as Effective Barrier against the Diffusion of Hydrogen from SiN_x:H Layers into Crystalline Silicon during Rapid Thermal Annealing

Atomic‐Layer‐Deposited Al₂O₃ as Effective Barrier against the Diffusion of Hydrogen from SiN_x:H Layers into Crystalline Silicon during Rapid Thermal Annealing