Surface passivation of n-type doped black silicon by atomic-layer-deposited SiO2/Al2O3 stacks

Abstract

Black silicon (b-Si) nanotextures can significantly enhance the light absorption of crystalline silicon solar cells. Nevertheless, for a successful application of b-Si textures in industrially relevant solar cell architectures, it is imperative that charge-carrier recombination at particularly highly n-type doped black Si surfaces is further suppressed. In this work, this issue is addressed through systematically studying lowly and highly doped b-Si surfaces, which are passivated by atomic-layer-deposited Al2O3 films or SiO2/Al2O3 stacks. In lowly doped b-Si textures, a very low surface recombination prefactor of 16 fA/cm2 was found after surface passivation by Al2O3. The excellent passivation was achieved after a dedicated wet-chemical treatment prior to surface passivation, which removed structural defects which resided below the b-Si surface. On highly n-type doped b-Si, the SiO2/Al2O3 stacks result in a considerable improvement in surface passivation compared to the Al2O3 single layers. The atomic-layer-deposited SiO2/Al2O3 stacks therefore provide a low-temperature, industrially viable passivation method, enabling the application of highly n- type doped b-Si nanotextures in industrial silicon solar cells.

Effective passivation of p+ and n+ emitters using SiO2/Al2O3/SiNx stacks: Surface passivation mechanisms and application to industrial p-PERT bifacial Si solar cells

“…It is worth noting that, such results were also found in B B r3or POCl3-diffused emitters in the author's previous unpublished study. The above results are also consistent with Ref.s [93,116,117,[125][126][127][128], which have mainly focused on the lab research and are based on different research perspectives, showing effective surface passivation of p-Si and n-Si using SiO2/Al2O3/(SiNx) synthesized by various methods.…”

“…The interfacial SiO2 is crucial for the excellent chemical passivation [11,13,122,123], and it can be either grown in-situ during ALD and post-anneal or grown ex-situ using a separate process of thermal oxidation, ALD, PECVD and chemical oxidation [11,13,115,117,122,124]. Thus, due to an excellent chemical passivation combined with a weak field-effect passivation, SiO2/Al2O3 can well passivate both n-Si [93,116,[125][126][127] and p-Si [116,117,128], which may bring a clear cost benefit in various structures such as IBC [53] and PERT [3,4] cells.…”

Black silicon back‐contact module with wide light acceptance angle

“…One of the major drawbacks of b‐Si is the difficulty to passivate the textured surface because of the high aspect ratio of nanostructures and the increase of Auger recombination in doped b‐Si regions due to high doping concentrations . In the last years, many efforts have been applied to obtain low recombination black silicon surfaces using either doped or nondoped nanostructures . For instance, MACE technique has been successfully applied to large‐area both‐side contacted DWS mc‐Si or CZ c‐Si solar cells with efficiencies more than 19% using phosphorous‐doped b‐Si passivated with plasma‐enhanced chemical vapor deposition (PECVD) SiN x.…”

“…8 In the last years, many efforts have been applied to obtain low recombination black silicon surfaces using either doped or nondoped nanostructures. [9][10][11][12] For instance, MACE technique has been successfully applied to large-area both-side contacted DWS mc-Si or CZ c-Si solar cells with efficiencies more than 19% using phosphorous-doped b-Si passivated with plasma-enhanced chemical vapor deposition (PECVD) SiN x.…”

Passivation of Phosphorus Diffused Black Multi‐Crystalline Silicon by Hafnium Oxide

“…Normally, the negative charge associated to Al 2 O 3 makes it unsuitable to passivate phosphorus diffusions. A stack of SiO 2 and Al 2 O 3 and a positively charged Al 2 O 3 /titanium oxide (TiO 2 ) stack deposited by ALD have both been demonstrated to passivate phosphorus diffused n + black Si surfaces, but a dielectric stack requires separate reactors in production to account for different process temperatures and avoid the risk of cross contamination.…”