Hydrogen passivation of defect-rich n-type Czochralski silicon and oxygen precipitates

Hallam, Brett; Abbott, Malcolm; Wenham, Stuart

doi:10.1016/j.solmat.2015.05.009

Cited by 36 publications

(21 citation statements)

References 42 publications

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“…These processes can remove detrimental transition metallic impurities such as iron from the bulk of the silicon . They can also allow for the passivation of a range of structural , impurity related , process‐induced and carrier‐induced defects . In contrast, many high‐efficiency n‐type technologies move away from processes that can enable gettering and hydrogenation of bulk silicon material, therefore requiring substrates with high initial bulk minority carrier lifetimes.…”

Section: Industrial Silicon Solar Cellsmentioning

confidence: 99%

“…Doing so could be considered as a pathway to (i) improve cell efficiencies and (ii) reduce cost through either an improvement in cell efficiency or a relaxation of the initial silicon material quality requirements. For example, recent work has demonstrated that n‐type silicon can significantly benefit from bulk hydrogenation, with increases the τ bulk of ‘low quality’ commercial grade n‐type wafers from 90 µs to 3.4 ms, suggesting that such wafers could be compatible with the fabrication of 24% efficient solar cells .…”

Section: Industrial Silicon Solar Cellsmentioning

confidence: 99%

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The role of hydrogenation and gettering in enhancing the efficiency of next‐generation Si solar cells: An industrial perspective

Hallam

Chen

Kim

et al. 2017

Physica Status Solidi (a)

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Phone: þ61 2 9385 0411, Fax: þ61 2 9385 7762We discuss the importance of gettering and hydrogenation for next-generation silicon solar cells in the context of industrial cell fabrication. Gettering and hydrogenation play a vital role for p-type cell technologies in improving the silicon material's minority charge carrier lifetime. These mechanisms are naturally incorporated during screen-printed cell fabrication through the phosphorus emitter diffusion, silicon nitride deposition and subsequent metallisation firing processes. While the transition towards emitters with lower dopant concentrations and/or thermal oxide passivation can reduce surface recombination, it can negatively impact the ability to getter common impurities such as iron. For cell technologies with alternative low-temperature metallisation approaches, the ability to hydrogenate bulk defects is greatly reduced. Ultrahigh efficiency n-type technologies tend to use heterojunction structures rather than diffused layers, but in doing so, do not benefit from phosphorus gettering. Also, particularly for amorphous silicon-based heterojunction structures, the imposed temperature constraints strongly limit the ability to passivate bulk defects. As a result, high-efficiency n-type technologies rely on the use of 'high-quality' wafers or would require the deliberate addition of gettering and hydrogenation processes before cell fabrication. A potential high-efficiency hybrid homojunction/heterojunction structure is then discussed that could naturally enable gettering and bulk hydrogenation throughout cell fabrication.Calibrated implied open circuit voltage (V oc ) map of a p-type mono-crystalline wafer highlighting the impact of prehydrogenating the top half of the wafer.

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Section: Industrial Silicon Solar Cellsmentioning

confidence: 99%

Section: Industrial Silicon Solar Cellsmentioning

confidence: 99%

The role of hydrogenation and gettering in enhancing the efficiency of next‐generation Si solar cells: An industrial perspective

Hallam

Chen

Kim

et al. 2017

Physica Status Solidi (a)

Self Cite

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“…[17,[20][21][22][23][24][25][26][27][28] Efficiency enhancements of 1-2 % absolute have been demonstrated on solar cells using hydrogen-containing dielectrics compared with those with non-hydrogen-containing dielectrics. [17,19] P-type monocrystalline silicon solar cells receive benefits of hydrogen passivation for process-induced defects such as oxygen precipitates [29,30] and the carrier-induced boron-oxygen (B-O) defect. [31,32] This defect forms under normal operating conditions in the field and can reduce cell performance by up to 2 % absolute.…”

Section: Hydrogen Passivation In Silicon Solar Cellsmentioning

confidence: 99%

“…[78,79] Although not explicitly discussed in those papers, the reduction in recombination activity is likely due to hydrogenation. [30] Although the industrial implementations of metallisation firing by Haunschild et al were not effective at eliminating all recombination activity of oxygen precipitates, an advanced hydrogenation firing process with modified power distribution to the lamps and also incorporating minority carrier injection during the cool-down was shown to eliminate the recombination activity of oxygen precipitates completely. [30] However, further work is required to investigate the specific impact of illumination on these defects.…”

Section: Hydrogenation Of Process-induced Defectsmentioning

confidence: 99%

“…5a shows a calibrated iV OC map of a sample with recombination-active oxygen precipitates directly after the deposition of PECVD SiN x :H, with the corresponding map after the subsequent high-temperature advanced hydrogenation process shown in Fig. 5b, where the recombination activity has been eliminated (see refs [30] and [80] for further details).…”

Section: Hydrogenation Of Process-induced Defectsmentioning

confidence: 99%

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Overcoming the Challenges of Hydrogenation in Silicon Solar Cells

et al. 2018

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The challenges of passivating defects in silicon solar cells using hydrogen atoms are discussed. Atomic hydrogen is naturally incorporated into conventional silicon solar cells through the deposition of hydrogen-containing dielectric layers and the metallisation firing process. The firing process can readily passivate certain structural defects such as grain boundaries. However, the standard hydrogenation processes are ineffective at passivating numerous defects in silicon solar cells. This difficulty can be attributed to the atomic hydrogen naturally occupying low-mobility and low-reactivity charge states, or the thermal dissociation of hydrogen–defect complexes. The concentration of the highly mobile and reactive neutral-charge state of atomic hydrogen can be enhanced using excess carriers generated by light. Additional low-temperature hydrogenation processes implemented after the conventional fast-firing hydrogenation process are shown to improve the passivation of difficult structural defects. For process-induced defects, careful attention must be paid to the process sequence to ensure that a hydrogenation process is included after the defects are introduced into the device. Defects such as oxygen precipitates that form during high-temperature diffusion and oxidation processes can be passivated during the subsequent dielectric deposition and high-temperature firing process. However, for laser-based processes performed after firing, an additional hydrogenation process should be included after the introduction of the defects. Carrier-induced defects are even more challenging to passivate, and advanced hydrogenation methods incorporating minority carrier injection must be used to induce defect formation first, and, second, provide charge state manipulation to enable passivation. Doing so can increase the performance of industrial p-type Czochralski solar cells by 1.1 % absolute when using a new commercially available laser-based advanced hydrogenation tool.

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Hydrogenation

Ciesla

2024

Photovoltaic Solar Energy

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Hydrogen passivation of defect-rich n-type Czochralski silicon and oxygen precipitates

Cited by 36 publications

References 42 publications

The role of hydrogenation and gettering in enhancing the efficiency of next‐generation Si solar cells: An industrial perspective

The role of hydrogenation and gettering in enhancing the efficiency of next‐generation Si solar cells: An industrial perspective

Overcoming the Challenges of Hydrogenation in Silicon Solar Cells

Hydrogenation

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