Recent insights into boron-oxygen related degradation: Evidence of a single defect

Hallam, Brett; Kim, Moonyong; Abbott, Malcolm; Nampalli, Nitin; Nærland, Tine Uberg; Stefani, Bruno Vicari; Wenham, Stuart

doi:10.1016/j.solmat.2017.06.038

Cited by 25 publications

(11 citation statements)

References 62 publications

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“…Control of the defects responsible for device degradation is of key importance for Si-based technologies as they have already achieved high-efficiency in large-area devices 51 . A well-documented mechanism is boron-oxygen LID, which is mainly observed in B-doped Czochralski (cz) grown Si [52][53][54] . Typical cz-Si samples contain oxygen impurities of around 10 18 cm -3 , much higher as compared to float-zone Si as quartz crucibles are used in the manufacture.…”

Section: Siliconmentioning

confidence: 99%

“…Typical cz-Si samples contain oxygen impurities of around 10 18 cm -3 , much higher as compared to float-zone Si as quartz crucibles are used in the manufacture. Various models have been suggested and examined to explain the degradation phenomena; however, there is no consensus on the atomistic process [52][53][54] . Substitution of Ga for B is found to be beneficial, but Ga has a worse segregation coefficient in Si than B 52 .…”

Section: Siliconmentioning

confidence: 99%

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Point defect engineering in thin-film solar cells

et al. 2018

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Control of defect processes in photovoltaic materials is essential for realising high-efficiency solar cells and related optoelectronic devices. The concentrations of native defects and extrinsic dopants tune the Fermi level and enable semiconducting p-n junctions; however, fundamental limits to doping exist in many compounds. Optical transitions involving defect states can enhance photocurrent generation through sub-bandgap absorption; however, such states are often responsible for carrier trapping and non-radiative recombination events that limit open-circuit voltage. Many classes of materialsincluding metal oxides, chalcogenides, and halidesare being examined for next-generation solar energy applications, and each technology faces distinct challenges that could benefit from point defect engineering. We review the evolution in point defect behaviour from Si-based photovoltaics to thin-film CdTe and Cu(In,Ga)Se2 technologies, through to the latest generation halide perovskite (CH3NH3PbI3) and kesterite (Cu2ZnSnS4) devices. We focus on the chemical bonding that underpins the defect chemistry, and the atomistic processes associated with the photophysics of charge carrier generation, trapping, and recombination in solar cells. Finally, we outline general principles to enable defect control in complex semiconducting materials.

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Section: Siliconmentioning

confidence: 99%

Section: Siliconmentioning

confidence: 99%

Point defect engineering in thin-film solar cells

et al. 2018

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“…[161][162][163] Furthermore, thermal processes are also known to precipitate iron. 158,164,165 Another defect of key importance for silicon solar cells with contradictions in the literature is the boron-oxygen (B-O) complex, 60,[166][167][168] responsible for carrier-induced degradation in ptype Czochralski (Cz) silicon. 169,170 The challenge of hydrogen detection has no doubt played a role in this controversy, with estimated defect concentrations in the range of 10 11 to 10 13 /cm Subsequent work has provided further evidence for the role of hydrogen, by identifying the influence of the hydrogen concentration and thickness of dielectric layers in the passivation reaction.…”

Section: E D = E C -0:16 Ev ð1þmentioning

confidence: 99%

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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“…With the identification of an additional stable high-lifetime state, a three-state model was developed to describe the B-O defect system [83]. This model has formed the basis for numerous studies investigating the kinetics of the B-O defect system [10,12,[85][86][87][88][89][90][91][92][93][94][95].…”

Section: Annealing Incorporating Minority Carrier Injectionmentioning

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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Recent insights into boron-oxygen related degradation: Evidence of a single defect

Cited by 25 publications

References 62 publications

Point defect engineering in thin-film solar cells

Point defect engineering in thin-film solar cells

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

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

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