Bulk lifetime and efficiency enhancement due to gettering and hydrogenation of defects during cast multicrystalline silicon solar cell fabrication

Sheoran, Manav; Upadhyaya, Ajay; Rohatgi, A.

doi:10.1016/j.sse.2007.10.001

Cited by 29 publications

(9 citation statements)

References 16 publications

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“…The TEM analyses have shown a high density of oxygen precipitates, sometimes decorated with metals. This confirms also that the impurities present in the form of precipitates (oxides and silicides) cannot be gettered out by Pdiffusion steps, as already observed by Sheoran et al [19].…”

Section: Samplesupporting

confidence: 88%

Oxygen distribution on a multicrystalline silicon ingot grown from upgraded metallurgical silicon

Sabatino

Binetti

Libal

et al. 2011

Solar Energy Materials and Solar Cells

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Section: Samplesupporting

confidence: 88%

Oxygen distribution on a multicrystalline silicon ingot grown from upgraded metallurgical silicon

Sabatino

Binetti

Libal

et al. 2011

Solar Energy Materials and Solar Cells

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“…The total dark saturation current density ( J 0 ) of all samples was 0.5–3.5 fA cm −2 , and hence the τ eff was limited by bulk recombination. The results highlight the complementary nature of gettering and hydrogenation for attacking orthogonal defects and hence the importance of using both methods to increase the bulk lifetime of p‐type silicon wafers, in agreement with previous studies . The corresponding improvement in the average iV OC was from 615 mV on the control samples to an impressive 689 mV on samples with gettering and hydrogenation.…”

Section: Active‐area J–v Parameters Of the Champion Cells Within Eachsupporting

confidence: 89%

Pre‐Fabrication Gettering and Hydrogenation Treatments for Silicon Heterojunction Solar Cells: A Possible Path to >700 mV Open‐Circuit Voltages Using Low‐Lifetime Commercial‐Grade p‐Type Czochralski Silicon

et al. 2018

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Pre-fabrication gettering and bulk hydrogenation processes are applied to lowbulk-lifetime (25 μs) p-type Czochralski silicon wafers before silicon heterojunction (SHJ) solar cell fabrication, resulting in effective minority carrier lifetime enhancements by a factor of six. On complete SHJ solar cells, this translates to an improvement in the open-circuit voltage (V OC ) of 71 mV, resulting in V OC values as high as 692 mV. This remarkably high V OC suggests that efficiencies approaching 25% could be possible for low-cost p-type Czochralski silicon wafersnot the typical expensive, high-quality n-type ones with lifetimes of several millisecondsin the near future. This method is also likely applicable to n-type SHJ solar cells to reduce the incoming wafer lifetime requirements and to other silicon solar cell structures featuring passivated contacts.Hydrogenated amorphous silicon (a-Si:H) thin films provide excellent surface passivation of crystalline silicon wafers. [1] This has enabled open-circuit voltages (V OC ) of 750 mV in silicon heterojunction (SHJ) solar cells [2] and resulted in multiple worldrecord efficiencies of over 25%, [3,4] with a current record of more than 26.6% using an interdigitated back-contact structure. [4] One attributed strength of the SHJ technology is the ability to fabricate cells at temperatures below 250 C to reduce processing costs and avoid "poisoning" the silicon bulk during high-temperature processes. [5,6] However, the exclusive use of low processing temperatureswhich is required because of the loss of hydrogen from the a-Si: H films at higher temperatureseliminates the possibility of improving the quality of the silicon bulk throughout the cell fabrication sequence with gettering and hydrogenation. This is primarily due to the low diffusion coefficients of impurities including hydrogen and iron at such temperatures. [7,8] As a result, to take full advantage of the excellent surface passivation offered by SHJ structures, highquality n-type Czochralski (Cz), or float-zone silicon wafers with millisecond starting lifetimes are required to make high-efficiency solar cells. [7] This strict wafer-lifetime requirement increases the solar cell production cost and limits SHJ cells to premium markets.To broaden the application of SHJ structures and reduce the high materials cost of n-type silicon wafers, p-type Cz silicon wafers could be used. In fact, p-type Cz wafers can have bulk lifetimes of over 1 ms [9] and can be used to fabricate solar cells with V OC s of up to 730 mV. [10] However, the commercial-grade p-type Cz wafers used for mass production of aluminium back-surface field (Al-BSF) and passivated emitter and rear cell (PERC) structures often have much lower lifetimes (below 200 ms), which lead to substantially lower V OC and efficiency values than those of their n-type counterparts. Despite these poor lifetimes, cells fabricated from these wafers have demonstrated V OC s of approximately 686 mVand record efficiencies of 22.7% using the PERC cell technology.

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“…This process acts to release hydrogen from the dielectric layers [103] and can enable the diffusion of hydrogen into the silicon and throughout the bulk [140][141][142][143]. The high temperatures used for co-firing, typically in the vicinity of 700-900 • C, overcome issues with trapping, significantly increase the generation of H 0 and enhance the diffusivity of hydrogen [111].…”

Section: Eliminating B-o Lid During Cell and Module Fabricationmentioning

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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Bulk lifetime and efficiency enhancement due to gettering and hydrogenation of defects during cast multicrystalline silicon solar cell fabrication

Cited by 29 publications

References 16 publications

Oxygen distribution on a multicrystalline silicon ingot grown from upgraded metallurgical silicon

Oxygen distribution on a multicrystalline silicon ingot grown from upgraded metallurgical silicon

Pre‐Fabrication Gettering and Hydrogenation Treatments for Silicon Heterojunction Solar Cells: A Possible Path to >700 mV Open‐Circuit Voltages Using Low‐Lifetime Commercial‐Grade p‐Type Czochralski Silicon

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

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