Easy-to-apply methodology to measure the hydrogen concentration in boron-doped crystalline silicon

Walter, Dominic; Bredemeier, Dennis; Falster, R.; Voronkov, V. V.; Schmidt, Jan

doi:10.1016/j.solmat.2019.109970

Cited by 37 publications

(39 citation statements)

References 12 publications

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“…We found that the misfit between experiment and simulation could be overcome by either increasing the total hydrogen concentration or decreasing the LeTID precursor concentration. The former would mean that the hydrogen concentration in the wafer is higher than expected from experiments [44]. As a consequence of the latter, the electron capture cross section σ e would have to be larger than 5 × 10 −14 cm −2 (and hence larger than that of all other defects) in order to explain observed very low lifetime values.…”

Section: Temporary Recoverymentioning

confidence: 87%

“…The starting conditions in the simulation, i.e., the total hydrogen concentration and, in particular, the relative share of the different hydrogen complexes have a significant impact on the LeTID dynamics. In order to begin with a realistic estimation, a firing process was emulated: A total hydrogen concentration [H] tot of 1 × 10 15 cm −3 (which is in the range of an expected concentration after a typical firing step [44]) was assumed to be in dissociated state at the peak temperature of 750°C. The redistribution of hydrogen to the different complexes was simulated for a cool-down rate of 100 K/s down to room temperature.…”

Section: Numerical Simulationsmentioning

confidence: 99%

“…The following notions about hydrogen reactions are taken from Voronkov and Falster [27] and Hamer et al [39], some of the parameter values were corrected using [44]. The hydrogen fractions in the different charge states were calculated according to Sun et al [42].…”

Section: A Implementation Of the Hydrogen Reactionsmentioning

confidence: 99%

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Temporary Recovery of the Defect Responsible for Light- and Elevated Temperature-Induced Degradation: Insights Into the Physical Mechanisms Behind LeTID

Kwapil

Schön

Niewelt

et al. 2020

IEEE J. Photovoltaics

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The effect of light-and elevated temperature-induced degradation (LeTID) can be nonpermanently reversed by charge carrier injection below the degradation temperature (commonly used degradation temperatures are above ∼70°C). In this study, we show that the rate of temporary recovery depends strongly on the excess carrier density. We observe that the order of the reaction changes from pseudo-zero to first with increasing injection. The rate decreases slightly with increasing temperature. Since the samples can go through multiple degradation/recovery cycles without distinct changes in the degradation kinetics, the experimentally accessible recovered and degraded states are interpreted as manifestations of the equilibrium concentrations of the defect responsible for LeTID at different temperatures. Based on our observations, we argue that the process underlying LeTID degradation is the dissociation of a precursor rather than an association of two or more components. In light of the relation between LeTID susceptibility and bulk hydrogen concentration, we hypothesize that the LeTID precursor dissociates into the LeTID defect and monatomic hydrogen. Numerical simulations of the coupled rate equations including hydrogen interactions well reproduce the experimental observations; according to these results, the presence of a sink for the atomic hydrogen such as dopant atoms is paramount for the LeTID degradation. Index Terms-Degradation, Defect reactions, light-and elevated temperature-induced degradation (LeTID), model, silicon defects. I. INTRODUCTION A FTER the first description of the phenomenon later termed light-and elevated temperature-induced degradation (LeTID) [1], extensive research has been conducted on the influences determining the LeTID extent and kinetics. Noting the

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Section: Temporary Recoverymentioning

confidence: 87%

Section: Numerical Simulationsmentioning

confidence: 99%

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Temporary Recovery of the Defect Responsible for Light- and Elevated Temperature-Induced Degradation: Insights Into the Physical Mechanisms Behind LeTID

Kwapil

Schön

Niewelt

et al. 2020

IEEE J. Photovoltaics

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“…In solar cells, the bulk H content has previously been estimated using Fourier Transform-IR (FT-IR) measurements via the reduction of hydrogen in the ARC after firing 18 or indirectly by its effect on the resistivity. 45 The first approach monitored changes in the IR absorption features due to Si-N, Si-H, and N-H before and after the firing process. In the second approach, the changes in the resistivity were assumed to arise from the conversion of hidden hydrogen, i.e., hydrogen in dimeric states that give weak or no IR absorbance, into monatomic H + which could then neutralize B dopants.…”

Section: Introductionmentioning

confidence: 99%

“…In the second approach, the changes in the resistivity were assumed to arise from the conversion of hidden hydrogen, i.e., hydrogen in dimeric states that give weak or no IR absorbance, into monatomic H + which could then neutralize B dopants. 8,34,45 One requires typically high concentrations of light-element impurities, e.g., 10 18 cm −3 in a 1-μm thick layer or 10 14 cm −3 in a 1 cm thick layer, in a bulk sample and measurements at cryogenic temperatures to detect their LVMs. 37 For silicon, it is also important to have surfaces polished to optical quality to reduce light scattering.…”

Section: Introductionmentioning

confidence: 99%

Hydrogen-related defects measured by infrared spectroscopy in multicrystalline silicon wafers throughout an illuminated annealing process

Weiser

Monakhov

Haug

et al. 2020

Journal of Applied Physics

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Hydrogen (H) is thought to be strongly involved in the light and elevated temperature-induced degradation observed predominantly in p-type silicon wafers, but the nature of the defect or defects involved in this process is currently unknown. We have used infrared (IR) spectroscopy to detect the vibrational signatures due to the H-B, H-Ga, and H 2 *(C) defects in thin, hydrogenated, p-type multicrystalline silicon wafers after increasing the optical path length by preparation and polishing the edges of a stack of wafers. The concentrations of the H-B and H-Ga acceptor complexes are reduced to 80% of their starting values after low intensity (5 mW/cm 2) illumination at room temperature for 96 h. Subsequent high intensity illumination (70 mW/cm 2) at 150°C for 7-8 h further decreases the concentrations of these defects; to ∼40% (H-B) and ∼50% (H-Ga) of their starting values. Our results show that, with careful sample preparation, IR spectroscopy can be used in conjunction with other techniques, e.g., quasisteady-state photoconductance, to investigate the involvement of different H-related point defects on degradation in solar-grade silicon wafers.

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Development of advanced hydrogenation processes for silicon solar cells via an improved understanding of the behaviour of hydrogen in silicon

Hallam

Hamer

Wenham

et al. 2020

Progress in Photovoltaics

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The understanding and development of advanced hydrogenation processes for silicon solar cells are presented. Hydrogen passivation is incorporated into virtually all silicon solar cells, yet the properties of hydrogen in silicon are still poorly understood. This is largely due to the complex behaviour of hydrogen in silicon and its ability to exist in many different forms in the lattice. For commercial solar cells, hydrogen is introduced into the device through the deposition of hydrogen-containing dielectric layers and the subsequent metallisation firing process. This process can readily passivate structural defects such as grain boundaries but is ineffective at passivating numerous defects in silicon solar cells such as the boron-oxygen complex, responsible for light-induced degradation in p-type Czochralski silicon. This difficulty is due to the need to first form the boron-oxygen defect and also due to atomic hydrogen naturally occupying low-mobility and low-reactivity charge states. However, these challenges can be overcome using advanced hydrogenation processes incorporating excess carrier generation from illumination or current injection that increase the concentration of the highly mobile and reactive neutral charge state. As a result, after fast firing, additional low-temperature advanced hydrogenation processes incorporating illumination can be implemented to enable the passivation of difficult defects like the boron-oxygen complex. With the implementation of such processes for industrial silicon solar cells, efficiency improvements of 1.1% absolute can be obtained.

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Easy-to-apply methodology to measure the hydrogen concentration in boron-doped crystalline silicon

Cited by 37 publications

References 12 publications

Temporary Recovery of the Defect Responsible for Light- and Elevated Temperature-Induced Degradation: Insights Into the Physical Mechanisms Behind LeTID

Temporary Recovery of the Defect Responsible for Light- and Elevated Temperature-Induced Degradation: Insights Into the Physical Mechanisms Behind LeTID

Hydrogen-related defects measured by infrared spectroscopy in multicrystalline silicon wafers throughout an illuminated annealing process

Development of advanced hydrogenation processes for silicon solar cells via an improved understanding of the behaviour of hydrogen in silicon

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