Polarized photoluminescence imaging analysis around small-angle grain boundaries in multicrystalline silicon wafers for solar cells

Kato, Gen; Tajima, Michio; Toyota, Hiroyuki; Ogura, Atsushi

doi:10.7567/jjap.53.080303

Cited by 9 publications

(9 citation statements)

References 20 publications

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“…This polarization effect is not observed at all grain boundaries, thus the geometrical effect identified by Peloso et al [14] is also not solely responsible for the effect. Our result is consistent with the recent observations of Kato et al [15] who report on the polarized nature of defect-band PL emission for both tilt and twist low angle GBs. However, our results further expand the understanding of these effects by showing that nearby high angle grain boundaries are not associated with any detectable polarized PL.…”

Section: Resultssupporting

confidence: 94%

“…The regions emitting lower band-to-band PL in Figure 1d show higher defect-band PL in Figure 1e which is small compared to the maximum and minimum intensities from defect PL emission of about ±300 units. Compared to the conventional approach, where the analyzer has to be manually set to a desired angle [15], the imaging tool presented here takes advantage of the digitized controller and can complete a full-wafer measurement in less than a minute.…”

Section: Methodsmentioning

confidence: 99%

“…These studies do not distinguish the types of defects in their measurements, or the relationship between the dislocation type, the dislocation microstructure, and the grain boundary structure. Kato et al, using a small field-of-view PL measurement system (that does not include simultaneous stress measurement), show a 90-degree difference in defect-band PL polarization angle between tilt and twist grain boundaries [15]. This recent work suggests that dislocation ordering in grain boundary structures may be responsible for polarization of the defect-band luminescence, but it does not consider the difference between small angle and high angle grain boundaries.…”

Section: Introductionmentioning

confidence: 99%

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Polarized light emission from grain boundaries in photovoltaic silicon

Lin

Rowe

Kaczkowski

et al. 2016

Extreme Mechanics Letters

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Some crystalline defects in photovoltaic silicon have deleterious effects on the energy conversion efficiency of the material. Distinguishing the harmful defects from the benign defects is a critical problem in the mechanics of materials for solar energy conversion. Interestingly, the visible light absorbed by silicon in the same part of the solar spectrum that is used to generate photocurrent, can also excite photoluminescence, which may be used to generate images of the microstructure. Slightly longer wavelengths in the near infrared (IR) may be used to measure strain in the material via photoelastic (PE) imaging. These two imaging modalities have recently been combined in a single instrument, and we show here the additional capability to identify and categorize defects directly by capturing the narrow band of photoluminescence emitted by regions of high dislocation density. We use this method to show that dislocations arranged in low angle grain boundaries emit polarized light, while dislocation structures in neighboring high angle grain boundaries do not emit polarized light. This capability may form the basis for nextgeneration, full-field optomechanics-based characterization of materials for solar energy conversion.

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Section: Resultssupporting

confidence: 94%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Polarized light emission from grain boundaries in photovoltaic silicon

Lin

Rowe

Kaczkowski

et al. 2016

Extreme Mechanics Letters

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“…Figure b shows a polar plot for the mc-Si wafer in which the D1/D2 and D3/D4 bands exhibit strong polarization behavior, with a 90° shift of intensity dependence. This is consistent with several previous works reported on the polarization of D-bands from mc-Si wafers, reflecting the anisotropic distribution of dislocations. − However, the DRL peaks observed in the Cz-Si wafers in this work do not exhibit any polarization phenomena, as shown for the 7 h growth-step annealed sample in Figure b. This could be due to dislocations in the vicinity of the oxygen precipitates being isotopically oriented, rather than preferentially oriented as in mc-Si .…”

Section: Resultssupporting

confidence: 93%

Impact of Gettering and Hydrogenation on Sub-Band-Gap Luminescence from Ring Defects in Czochralski-Grown Silicon

Basnet

Siriwardhana

Nguyen

et al. 2021

ACS Appl. Energy Mater.

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Ring defects often occur in n-type Czochralski-grown silicon wafers during intermediate- to high-temperature annealing and become more recombination-active with increasing anneal durations. Such defects can significantly reduce the efficiency of solar cells. In this work, low-temperature photoluminescence (PL) spectra were measured from such ring defects, which emit a broad defect-related luminescence (DRL) peak centered at 0.9 eV. Quantitative comparisons of the DRL peak area between samples are generally not possible when using a constant laser power due to the significantly different carrier lifetimes, resulting in a different injection level and peak intensity. We show that this complication may be circumvented by varying the excitation laser power to achieve a constant band–band PL intensity from each sample, resulting in the same average injection level. The broad DRL peaks were then deconvoluted into three individual component peaks centered at 0.88, 0.93, and 1 eV. The impact of hydrogenation and phosphorus diffusion gettering steps was investigated on the individual components of the DRL peaks. Both hydrogenation and phosphorus diffusion gettering steps suppressed the broad DRL peak. However, the individual deconvoluted peaks were suppressed to different degrees. We observed that when the component peak from the deeper energy level (0.88 eV) is dominant, the ring defects can be completely passivated by hydrogenation. However, when the component peaks from the shallower energy levels (0.93 and 1 eV) dominate the DRL peak, hydrogenation is less effective for the passivation of ring defects.

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“…Recently, as an alternative experimental method to CL measurements, a microscopic and spectroscopic mapping of dislocation related photoluminescence was proposed by the group of Tajima and co-workers 26 . The spatial resolution of the photoluminescence mapping is clearly lower than in CL images, but the photoluminescence investigations additionally allows the polarization of the deep level emission band correlated to dislocations to be determined in LAGBs with twist and tilt structures 27,28 .…”

Section: Discussionmentioning

confidence: 99%

Comprehensive Characterization of Extended Defects in Semiconductor Materials by a Scanning Electron Microscope

Hieckmann

Nacke

Allardt

et al. 2016

JoVE

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Extended defects such as dislocations and grain boundaries have a strong influence on the performance of microelectronic devices and on other applications of semiconductor materials. However, it is still under debate how the defect structure determines the band structure, and therefore, the recombination behavior of electron-hole pairs responsible for the optical and electrical properties of the extended defects. The present paper is a survey of procedures for the spatially resolved investigation of structural and of physical properties of extended defects in semiconductor materials with a scanning electron microscope (SEM). Representative examples are given for crystalline silicon. The luminescence behavior of extended defects can be investigated by cathodoluminescence (CL) measurements. They are particularly valuable because spectrally and spatially resolved information can be obtained simultaneously. For silicon, with an indirect electronic band structure, CL measurements should be carried out at low temperatures down to 5 K due to the low fraction of radiative recombination processes in comparison to non-radiative transitions at room temperature. For the study of the electrical properties of extended defects, the electron beam induced current (EBIC) technique can be applied. The EBIC image reflects the local distribution of defects due to the increased charge-carrier recombination in their vicinity. The procedure for EBIC investigations is described for measurements at room temperature and at low temperatures. Internal strain fields arising from extended defects can be determined quantitatively by cross-correlation electron backscatter diffraction (ccEBSD). This method is challenging because of the necessary preparation of the sample surface and because of the quality of the diffraction patterns which are recorded during the mapping of the sample. The spatial resolution of the three experimental techniques is compared.

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Polarized photoluminescence imaging analysis around small-angle grain boundaries in multicrystalline silicon wafers for solar cells

Cited by 9 publications

References 20 publications

Polarized light emission from grain boundaries in photovoltaic silicon

Polarized light emission from grain boundaries in photovoltaic silicon

Impact of Gettering and Hydrogenation on Sub-Band-Gap Luminescence from Ring Defects in Czochralski-Grown Silicon

Comprehensive Characterization of Extended Defects in Semiconductor Materials by a Scanning Electron Microscope

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