TY - JOUR

T1 - Light Trapping and Surface Passivation of Micron-Scaled Macroporous Blind Holes

AU - Schafer, Soren

AU - Gemmel, Catherin

AU - Kajari-Schroder, Sarah

AU - Brendel, Rolf

N1 - Funding Information: The authors would like to thank Moises Garin from Univer- sitat Polit‘ecnica de Catalunya, Barcelona, Spain, for his help with the prestructuring process. S. Sch¤afer thanks M. Garin and R. Alcubilla from Universitat Polit‘ecnica de Catalunya, Barcelona, Spain, for their hospitality during a visiting intern- ship and for fruitful discussions. This work was supported by the Federal Ministry for Economic Affairs and Energy under the contract FKZ 0325461

PY - 2016/3

Y1 - 2016/3

N2 - We fabricate a blind hole surface texture by anodic etching of macroporous Si. The blind holes, i.e., pores that do not penetrate the wafer completely, have an average diameter of 2.7 μm, a distance of 4 μm, and a depth of 9 μm. This texture is capable of reducing the AM1.5G photon flux-weighted front reflectance to 1.5% without depositing an antireflection coating. The μm-feature size makes it a less fragile alternative to common nm-sized black silicon structures. We passivate the blind holes by atomic layer deposited AlOx. The blind hole texture allows for a carrier lifetime of (2.2 ± 0.25) ms corresponding to an effective surface recombination velocity of (8 ± 1.5) cm/s with respect to the macroscopic front surface. A direct comparison of the optical performance and the surface passivation quality with a standard SiNx-coated random pyramid surface shows that blind holes allow for a relative efficiency gain of (3 ± 0.2)% when applied, e.g., in an otherwise perfect back-contacted solar cell.

AB - We fabricate a blind hole surface texture by anodic etching of macroporous Si. The blind holes, i.e., pores that do not penetrate the wafer completely, have an average diameter of 2.7 μm, a distance of 4 μm, and a depth of 9 μm. This texture is capable of reducing the AM1.5G photon flux-weighted front reflectance to 1.5% without depositing an antireflection coating. The μm-feature size makes it a less fragile alternative to common nm-sized black silicon structures. We passivate the blind holes by atomic layer deposited AlOx. The blind hole texture allows for a carrier lifetime of (2.2 ± 0.25) ms corresponding to an effective surface recombination velocity of (8 ± 1.5) cm/s with respect to the macroscopic front surface. A direct comparison of the optical performance and the surface passivation quality with a standard SiNx-coated random pyramid surface shows that blind holes allow for a relative efficiency gain of (3 ± 0.2)% when applied, e.g., in an otherwise perfect back-contacted solar cell.

KW - Charge carrier lifetime

KW - optical losses

KW - optical reflectivity

KW - Surface texture

UR - http://www.scopus.com/inward/record.url?scp=84951335200&partnerID=8YFLogxK

U2 - 10.1109/JPHOTOV.2015.2505179

DO - 10.1109/JPHOTOV.2015.2505179

M3 - Article

AN - SCOPUS:84951335200

VL - 6

SP - 397

EP - 403

JO - IEEE journal of photovoltaics

JF - IEEE journal of photovoltaics

SN - 2156-3381

IS - 2

M1 - 7360866

ER -