Accelerated formation of the boron–oxygen complex in p‐type Czochralski silicon

Hamer, Phillip; Hallam, Brett; Abbott, Malcolm; Wenham, Stuart

doi:10.1002/pssr.201510064

Cited by 35 publications

(26 citation statements)

References 19 publications

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“…formation and passivation appears to be similar to that recently shown for the BO defect in Cz silicon [12] in the sense that the defect must be formed prior to passivation, and that increased illumination and elevated temperatures can be used to accelerate the degradation. However, in the case of mc-Si, the timescales are substantially increased.…”

mentioning

confidence: 54%

Acceleration and mitigation of carrier-induced degradation in p-type multi-crystalline silicon

Payne

Chan

Hallam

et al. 2016

Phys. Status Solidi RRL

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Recently, a new carrier‐induced defect has been reported in multi‐crystalline silicon (mc‐Si), and has been shown to be particularly detrimental to the performance of passivated emitter and rear contact (PERC) cells. Under normal conditions, this defect can take years to fully form. This Letter reports on the accelerated formation and subsequent passivation of this carrier‐induced defect through the use of high illumination intensity and elevated temperatures resulting in passivation within minutes. The process was tested on industrial mc‐Si PERC solar cells, where degradation after a 100 hour stability test was suppressed to only 0.1% absolute compared to 2.1% for non‐treated cells. (© 2016 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim)

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mentioning

confidence: 54%

Acceleration and mitigation of carrier-induced degradation in p-type multi-crystalline silicon

Payne

Chan

Hallam

et al. 2016

Phys. Status Solidi RRL

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“…[113] An example showing the impact of advanced hydrogenation processes for eliminating B-O-related degradation is shown in Table 2. The cells that received an AHP process to eliminate B-O-related carrier-induced degradation show a higher efficiency (20.54 %) after the AHP and subsequent accelerated stability test [98] compared with the initial efficiency (20.11 %). This increase was related to significant increases in the V OC and short circuit current (J SC ) of the devices, indicating the passivation of additional defects in the device.…”

Section: Hydrogenation Of Carrier-induced Defectsmentioning

confidence: 97%

“…In 2009, Münzer identified a critical role of hydrogen during illuminated annealing, whereby the permanent deactivation only occurred in solar cells fabricated using hydrogen-rich SiN x :H grown by PECVD, and not those using hydrogen-lean SiN x :H grown by low-pressure chemical vapour deposition (LPCVD). [32] Further work by multiple authors has highlighted the influence of the hydrogen concentration and thickness of dielectric layers in the passivation, [16,96,97] the dependence of the passivation rate on the illumination intensity (separately from the role for defect formation [95,98] ), and the correlation between the passivation rate and the theoretical concentration of H 0 . [31,33,60,99,100] The importance of illuminated annealing has also been noted for a more recently identified degradation mechanism.…”

Section: Hydrogenation Of Carrier-induced Defectsmentioning

confidence: 99%

“…[110] In contrast, by accelerating the defect formation rate using high-intensity illumination, a substantially higher temperature can be used, which results in a further reduction in the time to form the defects. [72,98,100] Using such a process, B-O defects can be completely formed and passivated on finished industrial screen-printed solar cells in less than 8 s, [72,100,113] which can improve cell performance of industrial cells in the vicinity of 1 % absolute. [113] This has seen the development of new halogen-, light-emitting diode (LED)-, and laser-based industrial advanced hydrogenation tools for the mitigation of B-O-related degradation.…”

Section: Hydrogenation Of Carrier-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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“…Above such excess electron concentrations, the reaction rate in p-type silicon is determined by the background boron-doping concentration, typically on the order of 1 × 10 16 cm −3 . However, Hamer et al demonstrated that this fundamental limit of the defect formation rate imposed by the background doping concentration could be overcome by driving the silicon into high-injection conditions using high-intensity laser illumination [131]. It was proposed that the increased reaction rate with high-intensity illumination could be due to a dependence of the reaction rate on the total hole concentration, rather than the equilibrium hole concentration.…”

Section: Role Of Defect Formationmentioning

confidence: 99%

Eliminating Light-Induced Degradation in Commercial p-Type Czochralski Silicon Solar Cells

et al. 2017

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This paper discusses developments in the mitigation of light-induced degradation caused by boron-oxygen defects in boron-doped Czochralski grown silicon. Particular attention is paid to the fabrication of industrial silicon solar cells with treatments for sensitive materials using illuminated annealing. It highlights the importance and desirability of using hydrogen-containing dielectric layers and a subsequent firing process to inject hydrogen throughout the bulk of the silicon solar cell and subsequent illuminated annealing processes for the formation of the boron-oxygen defects and simultaneously manipulate the charge states of hydrogen to enable defect passivation. For the photovoltaic industry with a current capacity of approximately 100 GW peak, the mitigation of boron-oxygen related light-induced degradation is a necessity to use cost-effective B-doped silicon while benefitting from the high-efficiency potential of new solar cell concepts.

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Accelerated formation of the boron–oxygen complex in p‐type Czochralski silicon

Cited by 35 publications

References 19 publications

Acceleration and mitigation of carrier-induced degradation in p-type multi-crystalline silicon

Acceleration and mitigation of carrier-induced degradation in p-type multi-crystalline silicon

Overcoming the Challenges of Hydrogenation in Silicon Solar Cells

Eliminating Light-Induced Degradation in Commercial p-Type Czochralski Silicon Solar Cells

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