TY - JOUR

T1 - Impact of hydrogen on the boron-oxygen-related lifetime degradation and regeneration kinetics in crystalline silicon

AU - Helmich, Lailah

AU - Walter, Dominic C.

AU - Falster, Robert

AU - Voronkov, Vladimir V.

AU - Schmidt, Jan

N1 - Funding Information: The authors thank C. Marquardt for sample processing (cleaning, etching, diffusion).This work was funded by the German State of Lower Saxony and the German Federal Ministry for Economic Affairs and Energy (BMWi) within the research project “LIMES” under contract No. 0324204D . The content is the responsibility of the authors.

PY - 2021/10

Y1 - 2021/10

N2 - We examine the impact of hydrogen on the boron-oxygen-related lifetime degradation and regeneration kinetics in boron-doped p-type Czochralski-grown silicon wafers. We introduce the hydrogen into the silicon bulk by rapid thermal annealing. The hydrogen source are hydrogen-rich silicon nitride (SiN x:H) layers. Aluminum oxide (Al 2O 3) layers of varying thickness are placed in-between the silicon wafer surfaces and the SiN x:H layers. By varying the Al 2O 3 thickness, which acts as an effective hydrogen diffusion barrier, the hydrogen bulk content is varied over more than one order of magnitude. The hydrogen content is determined from measured wafer resistivity changes. In order to examine the impact of hydrogen on the degradation kinetics, all samples are illuminated at a light intensity of 0.1 suns near room temperature. We observe no impact of the in-diffused hydrogen content on the degradation rate constant, confirming that hydrogen is not involved in the boron-oxygen degradation mechanism. The regeneration experiments at 160°C and 1 sun, however, show a clear dependence on the hydrogen content with a linear increase of the regeneration rate constant with increasing bulk hydrogen concentration. However, extrapolation of our measurements toward a zero in-diffused hydrogen content shows that the regeneration is still working even without any in-diffused hydrogen. Hence, our measurements demonstrate that there are two distinct regeneration processes taking place. This is in good agreement with a recently proposed defect reaction model and is also in agreement with the finding that the permanent boron-oxygen deactivation also works on non-fired solar cells, though at a lower rate.

AB - We examine the impact of hydrogen on the boron-oxygen-related lifetime degradation and regeneration kinetics in boron-doped p-type Czochralski-grown silicon wafers. We introduce the hydrogen into the silicon bulk by rapid thermal annealing. The hydrogen source are hydrogen-rich silicon nitride (SiN x:H) layers. Aluminum oxide (Al 2O 3) layers of varying thickness are placed in-between the silicon wafer surfaces and the SiN x:H layers. By varying the Al 2O 3 thickness, which acts as an effective hydrogen diffusion barrier, the hydrogen bulk content is varied over more than one order of magnitude. The hydrogen content is determined from measured wafer resistivity changes. In order to examine the impact of hydrogen on the degradation kinetics, all samples are illuminated at a light intensity of 0.1 suns near room temperature. We observe no impact of the in-diffused hydrogen content on the degradation rate constant, confirming that hydrogen is not involved in the boron-oxygen degradation mechanism. The regeneration experiments at 160°C and 1 sun, however, show a clear dependence on the hydrogen content with a linear increase of the regeneration rate constant with increasing bulk hydrogen concentration. However, extrapolation of our measurements toward a zero in-diffused hydrogen content shows that the regeneration is still working even without any in-diffused hydrogen. Hence, our measurements demonstrate that there are two distinct regeneration processes taking place. This is in good agreement with a recently proposed defect reaction model and is also in agreement with the finding that the permanent boron-oxygen deactivation also works on non-fired solar cells, though at a lower rate.

KW - Boron-oxygen defect

KW - Carrier lifetime

KW - Czochralski-grown silicon

KW - Hydrogen

KW - LID

KW - Regeneration

UR - http://www.scopus.com/inward/record.url?scp=85114049957&partnerID=8YFLogxK

U2 - 10.1016/j.solmat.2021.111340

DO - 10.1016/j.solmat.2021.111340

M3 - Article

AN - SCOPUS:85114049957

VL - 232

JO - Solar Energy Materials and Solar Cells

JF - Solar Energy Materials and Solar Cells

SN - 0927-0248

M1 - 111340

ER -