Taking monocrystalline silicon to the ultimate lifetime limit

Niewelt, Tim; Richter, Armin; Kho, Teng; Grant, Nicholas E.; Bonilla, Ruy S.; Steinhauser, Bernd; Polzin, Jana‐Isabelle; Feldmann, Frank; Hermle, Martin; Murphy, John D.; Phang, Sieu Pheng; Kwapil, Wolfram; Schubert, Martin C.

doi:10.1016/j.solmat.2018.05.040

Cited by 48 publications

(41 citation statements)

References 39 publications

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“…In this experiment, iVOC values up to 739 mV after hydrogenation and stripping of the SiNx:H layer were reached, corresponding to a τeff@10 15 cm -3 of 3260 μs, a J0 of 2.7 ± 0.7 fA/cm 2 and a Seff@10 15 cm -3 of 3 cm/s. According to literature, these values correspond to state-of-the-art passivation levels of p-type silicon wafers [36,[53][54][55][56][57][58][59][60][61]. Note also that the present samples have no in-diffused doped region, as stated previously, and that these oxides were grown at 900 °C, a comparably low temperature, and without addition of trichloroethane (TCA).…”

Section: Study Of the Influence Of The Sicx Layer's Doping On The Hydsupporting

confidence: 77%

Analysis of hydrogen distribution and migration in fired passivating contacts (FPC)

Lehmann

Valle

Horzel

et al. 2019

Solar Energy Materials and Solar Cells

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High temperature passivating contacts for c-Si based solar cells are intensively studied because of their potential in boosting solar cell efficiency while being compatible with industrial processes at high temperatures. In this work, the hydrogenation mechanism of fired passivating contacts (FPC) based on c-Si/SiOx/nc-SiCx(p) stacks was investigated. More specifically, the correlation between passivation and local re-distribution of hydrogen resulting from the application of different types of interfacial oxides (SiOx) and post-hydrogenation processes were analyzed. To do so, the applied processing sequence was interrupted at different stages in order to characterize the samples. To assess the hydrogen content, deuterium was introduced (alongside/instead of hydrogen) and secondary ion mass spectroscopy (SIMS) was used for depth profiling. Combining these results with lifetime measurements, the key role played by hydrogen in the passivation of defects at the c-Si/SiOx interface is discussed. The SIMS profiles show that hydrogen almost completely effuses out of the SiCx(p) during firing, but can be reintroduced by hydrogenation via forming gas anneal (FGA) or by release from a hydrogen containing layer such as SiNx:H. A pile-up of H at the c-Si/SiOx interface was observed and identified as a key element in the FPC's passivation mechanism. Moreover, the samples hydrogenated with SiNx:H exhibited higher H content compared to those treated by FGA, resulting in higher iVOC values. Further investigations revealed that the doping of the SiCx layer does not affect the amount of interfacial defects passivated by the hydrogenation process presented in this work. Eventually, an effect of the oxide's nature on passivation quality is evidenced. iVOC values of up to 706 mV and 720 mV were reached with FPC test structures using chemical and UV-O3 tunneling oxides, respectively, and up to 739 mV using a reference passivation sample featuring a ~25 nm thick thermal oxide.

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Section: Study Of the Influence Of The Sicx Layer's Doping On The Hydsupporting

confidence: 77%

Analysis of hydrogen distribution and migration in fired passivating contacts (FPC)

Lehmann

Valle

Horzel

et al. 2019

Solar Energy Materials and Solar Cells

View full text Add to dashboard Cite

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“…Furthermore, it will be shown that the bulk lifetime can be stabilized against subsequent thermal processing at significantly lower temperatures (900 °C) than the conventionally used 30–60 min annealing at around 1050 °C. [ 12–16 ] The defect annihilation is also found to be fast (sub‐second timescale), although a fraction of the defects reappears during a subsequent degradation annealing. Together with N‐quantification measurements by secondary ion mass spectrometry (SIMS), it is concluded that at high temperatures the V x N y ‐centers dissociate, accompanied by an out‐diffusion of nitrogen from the Si‐wafer.…”

Section: Introductionmentioning

confidence: 99%

Kinetics of Bulk Lifetime Degradation in Float‐Zone Silicon: Fast Activation and Annihilation of Grown‐In Defects and the Role of Hydrogen versus Light

Hiller

Markevich

Guzman

et al. 2020

Physica Status Solidi (a)

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Float‐zone (FZ) silicon often has grown‐in defects that are thermally activated in a broad temperature window (≈300–800 °C). These defects cause efficient electron‐hole pair recombination, which deteriorates the bulk minority carrier lifetime and thereby possible photovoltaic conversion efficiencies. Little is known so far about these defects which are possibly Si‐vacancy/nitrogen‐related (VxNy). Herein, it is shown that the defect activation takes place on sub‐second timescales, as does the destruction of the defects at higher temperatures. Complete defect annihilation, however, is not achieved until nitrogen impurities are effused from the wafer, as confirmed by secondary ion mass spectrometry. Hydrogenation experiments reveal the temporary and only partial passivation of recombination centers. In combination with deep‐level transient spectroscopy, at least two possible defect states are revealed, only one of which interacts with H. With the help of density functional theory V1N1‐centers, which induce Si dangling bonds (DBs), are proposed as one possible defect candidate. Such DBs can be passivated by H. The associated formation energy, as well as their sensitivity to light‐induced free carriers, is consistent with the experimental results. These results are anticipated to contribute to a deeper understanding of bulk‐Si defects, which are pivotal for the mitigation of solar cell degradation processes.

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“…For oxidized silicon, this can be partly explained by the fact that 10 nm SiO 2 is grown at 850 °C rather than 1050 °C. Recent reports have found that higher temperature oxidation annihilates in‐grown defects in FZ silicon, providing a stable and higher quality benchmark for surface passivation studies . For the a‐Si and AlO x structures, this can be explained by the plasma damage occurring during film deposition as has also been reported .…”

Section: Carrier‐dependent Surface Recombination In Siliconmentioning

confidence: 67%

Controlling Surface Carrier Density via a PEDOT:PSS Gate: An Application to the Study of Silicon‐Dielectric Interface Recombination

Bonilla

2018

Solar RRL

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This communication reports a technique to control the surface carrier population of silicon during photo‐conductance decay measurements, by using a semi‐transparent PEDOT:PSS gate. The potential of this technique has been demonstrated by characterizing carrier‐dependent surface recombination of 1 Ω cm n‐type float zone silicon, passivated with dielectric stack layers of either SiO2, SiO2/SiNx, a‐Si/SiOx, a‐Si/SiOx/SiNx, AlOx, or AlOx/SiNx. Carrier density at the Si‐dielectric interface has been controlled from heavy inversion to heavy accumulation regimes despite leakage currents. This has provided insightful information into the recombination activity at the silicon surface.

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Taking monocrystalline silicon to the ultimate lifetime limit

Cited by 48 publications

References 39 publications

Analysis of hydrogen distribution and migration in fired passivating contacts (FPC)

Analysis of hydrogen distribution and migration in fired passivating contacts (FPC)

Kinetics of Bulk Lifetime Degradation in Float‐Zone Silicon: Fast Activation and Annihilation of Grown‐In Defects and the Role of Hydrogen versus Light

Controlling Surface Carrier Density via a PEDOT:PSS Gate: An Application to the Study of Silicon‐Dielectric Interface Recombination

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