TY - JOUR

T1 - Role of oxygen in the UV-ps laser triggered amorphization of poly-Si for Si solar cells with local passivated contacts

AU - Schäfer, Sören

AU - Mercker, Anja

AU - Köhler, Adrian

AU - Neubert, Tobias

AU - Mettner, Larissa

AU - Wolpensinger, Bettina

AU - Mertens, Verena

AU - Peibst, Robby

N1 - Funding Information: We acknowledge the Laboratory of Nano and Quantum Engineering (LNQE) of Leibniz Universität Hannover for support with TEM measurements and Andrea Lissel from LNQE Hannover for TEM sample preparation, David Sylla from ISFH for laser process support, Arne Dittrich from ISFH for support with determining the diffuse reflectance fraction, Sascha Wolter and Marvin Diederich from ISFH for support with the Raman measurements, and Jan Krügener from MBE Hannover for fruitful discussions on Raman measurements. Furthermore, we thank Rolf Brendel for his continuous support of PV research at ISFH. This work is funded by the German Federal Ministry for Economic Affairs and Energy under Grant FKZ No. 0324274B (Genesis).

PY - 2021/4/7

Y1 - 2021/4/7

N2 - In recent years, poly-Si based passivated contacts elevated the conversion efficiencies of crystalline Si solar cells to levels of 26%abs due to their outstanding electrical surface passivation performance and current transport characteristics. A major associated challenge, however, is the large parasitic light absorption within the doped poly-Si, regardless if the contacts are applied on the front and/or on the rear side of the solar cell. It, therefore, might be beneficial to confine the passivated contacts to local regions underneath the metal contacts. We present an effective and flexible laser-based approach to structure the poly-Si layer after its full-area deposition. Laser pulses with a pulse duration of 9 ps and a wavelength of 355 nm trigger an amorphization of the poly-Si surface. The minimum threshold fluence for amorphization is between 89 and 129 mJ/cm2. The a-Si layer, which is laterally homogeneous and up to (33 ± 4) nm in thickness, works as an etch barrier in an alkaline solution. The most robust barrier corresponding to the maximum thickness of the a-Si layer is found for a fluence of (270 ± 30) mJ/cm2. Besides the impact of the laser fluence on the etch resistiveness of the modified poly-Si layer, we study the role of oxygen during the laser process. We find that oxygen becomes incorporated into the material for certain laser fluences, which results in a more robust etch barrier. The amount of oxygen incorporated is below 3 wt. %. Eventually, we present a phenomenological model of our findings.

AB - In recent years, poly-Si based passivated contacts elevated the conversion efficiencies of crystalline Si solar cells to levels of 26%abs due to their outstanding electrical surface passivation performance and current transport characteristics. A major associated challenge, however, is the large parasitic light absorption within the doped poly-Si, regardless if the contacts are applied on the front and/or on the rear side of the solar cell. It, therefore, might be beneficial to confine the passivated contacts to local regions underneath the metal contacts. We present an effective and flexible laser-based approach to structure the poly-Si layer after its full-area deposition. Laser pulses with a pulse duration of 9 ps and a wavelength of 355 nm trigger an amorphization of the poly-Si surface. The minimum threshold fluence for amorphization is between 89 and 129 mJ/cm2. The a-Si layer, which is laterally homogeneous and up to (33 ± 4) nm in thickness, works as an etch barrier in an alkaline solution. The most robust barrier corresponding to the maximum thickness of the a-Si layer is found for a fluence of (270 ± 30) mJ/cm2. Besides the impact of the laser fluence on the etch resistiveness of the modified poly-Si layer, we study the role of oxygen during the laser process. We find that oxygen becomes incorporated into the material for certain laser fluences, which results in a more robust etch barrier. The amount of oxygen incorporated is below 3 wt. %. Eventually, we present a phenomenological model of our findings.

UR - http://www.scopus.com/inward/record.url?scp=85103784267&partnerID=8YFLogxK

U2 - 10.1063/5.0045829

DO - 10.1063/5.0045829

M3 - Article

AN - SCOPUS:85103784267

VL - 129

JO - Journal of applied physics

JF - Journal of applied physics

SN - 0021-8979

IS - 13

M1 - 133103

ER -