Shape and quality of Si single bulk crystals grown inside Si melts using the noncontact crucible method

Nakajima, Kazuo; Murai, Ryosuke; Ono, Satoshi; Morishita, Kohei; Kivambe, Maulid; Powell, Douglas M.; Buonassisi, Tonio

doi:10.7567/jjap.54.015504

Cited by 22 publications

(4 citation statements)

References 22 publications

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“…We assume this relatively high lifetime in order to determine limiting efficiencies solely due to the presence of dislocations. We also note that lifetimes this high have been reported in several materials that have significantly higher dislocation density than CZ-Si, including epi-Si [23,24], QSC-Si [25], n-type mc-Si [8], and silicon grown by the so-called "noncontact-crucible method" [26,27]. While p-type mc-Si has not yet achieved wafer-averaged millisecond lifetimes, lifetime has increased dramatically in recent years and is now approaching 1 ms [28].…”

Section: Fig 1 Schematic Of Dislocation Simulation (A)supporting

confidence: 53%

Dislocation-limited performance of advanced solar cells determined by TCAD modeling

Needleman

Wagner

Altermatt³

et al. 2016

Solar Energy Materials and Solar Cells

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In recent years, low-cost silicon for photovoltaic applications has trended toward smaller grain sizes with lower dislocation densities. These changes, coupled with advanced device architectures like heterojunction and passivated emitter and rear cells, have enabled higher efficiencies, including new world records. To establish material requirements for further improvement, we model dislocations with different recombination strengths in Sentaurus Device using mid-gap defects spatially localized at the nanoscale in three dimensions. This approach accounts for the charging of dislocations and differentiates between dislocations and grain boundaries or metal impurities. Simulations that model dislocations as macroscopic variations in effective bulk lifetime or diode parameters do not address these issues. We validate our model by simulating the world record multicrystalline silicon solar cell. We find that three parameters influence cell efficiency: the area fraction of the cell containing dislocations, the dislocation density within defect clusters, and the concentration of recombination centers at these dislocations. We provide targets for these parameters and show how our results can be used to determine the potential gains from reducing dislocations in experimental devices and materials. We further predict that device architectures that lead to higher-injection, such as silicon heterojunction cells, are more robust to the presence of dislocations.

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Section: Fig 1 Schematic Of Dislocation Simulation (A)supporting

confidence: 53%

Dislocation-limited performance of advanced solar cells determined by TCAD modeling

Needleman

Wagner

Altermatt³

et al. 2016

Solar Energy Materials and Solar Cells

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“…The dominant defect type in the material is a swirl‐defect, also observed in Cz ingots and likely caused by thermal gradients during crystal growth. Apart from the swirl defect, a low overall dislocation density <10 3 cm −2 has been observed in NOC material, leaving potential to achieve high efficiency devices .…”

Section: Millisecond Lifetimes In Unconventional Wafers Enabled By Dementioning

confidence: 99%

Material requirements for the adoption of unconventional silicon crystal and wafer growth techniques for high‐efficiency solar cells

Hofstetter

Cañizo

Wagner

et al. 2015

Progress in Photovoltaics

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Silicon wafers comprise approximately 40% of crystalline silicon module cost and represent an area of great technological innovation potential. Paradoxically, unconventional wafer-growth techniques have thus far failed to displace multicrystalline and Czochralski silicon, despite four decades of innovation. One of the shortcomings of most unconventional materials has been a persistent carrier lifetime deficit in comparison to established wafer technologies, which limits the device efficiency potential. In this perspective article, we review a defect-management framework that has proven successful in enabling millisecond lifetimes in kerfless and cast materials. Control of dislocations and slowly diffusing metal point defects during growth, coupled to effective control of fast-diffusing species during cell processing, is critical to enable high cell efficiencies. To accelerate the pace of novel wafer development, we discuss approaches to rapidly evaluate the device efficiency potential of unconventional wafers from injection-dependent lifetime measurements.

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“…[1][2][3][4][5][6][7][8] This method is similar to the Kyropoulos method. [9][10][11] In the NOC method, however, a low-temperature region must be intentionally established in a Si melt.…”

Section: Introductionmentioning

confidence: 99%

“…When the evaporation of oxygen from the surface of the Si melt is the main mechanism reducing the oxygen concentration of ingots, the oxygen concentration should increase with the diameter ratio. 8 For the present furnace, in which little convection is expected, we determined the diameter ratio dependence of the oxygen concentration in ingots when a diameter ratio was more than 0.6. The mechanism by which a large low temperature region is formed systematically discussed.…”

Section: Introductionmentioning

confidence: 99%

Growth of Si Bulk Crystals with Large Diameter Ratio Using Small Crucibles by Creating a Large Low-Temperature Region Inside a Si Melt Contained in an NOC Furnace Developed Using Two Zone Heaters

Nakajima¹,

Ono²,

Murai³

et al. 2016

Journal of Elec Materi

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Three zone heaters were generally used for a noncontact crucible (NOC) furnace. For practical reasons a simpler NOC furnace was developed with two zone heaters, which had a carbon heat holder to cover the three roles of each heater. Large low-temperature regions were obtained, and silicon ingots were grown in small crucibles with a large diameter and diameter ratio. Here, the diameter ratio is the ratio of the ingot diameter to the crucible diameter and can be as large as 0.90. The diameter ratio was controlled mainly by the temperature reduction of the first heater. Power changes of the second heater did not have a significant impact on the ingot diameter. Using this NOC furnace, maximum ingot diameters of 28.0, 33.5, and 45.0 cm were obtained using crucibles of 33, 40, and 50 cm in diameter, respectively. The oxygen concentration of the ingots did not strongly depend on the diameter ratio and were always low because convection in the Si melt was markedly suppressed by the carbon heat holder. Moreover, the oxygen concentration of the ingots has a tendency to become lower as the crucible diameter becomes larger.

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Shape and quality of Si single bulk crystals grown inside Si melts using the noncontact crucible method

Cited by 22 publications

References 22 publications

Dislocation-limited performance of advanced solar cells determined by TCAD modeling

Dislocation-limited performance of advanced solar cells determined by TCAD modeling

Material requirements for the adoption of unconventional silicon crystal and wafer growth techniques for high‐efficiency solar cells

Growth of Si Bulk Crystals with Large Diameter Ratio Using Small Crucibles by Creating a Large Low-Temperature Region Inside a Si Melt Contained in an NOC Furnace Developed Using Two Zone Heaters

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