Destruction and also regrowth in polysilicon passivation layers

• Scientists in Australia took a close consider the long-term efficiency of passivation layers in silicon solar cells, as well as found a surprising procedure of degradation and regrowth at the office within the product. The outcomes could have ramifications on the procedures used in industrial scale solar cell manufacturing.

Researchers led by Australia National University (ANU) have made a number of new monitorings on the destruction habits of passivation layers in silicon solar cells. These include the existence of a degradation and succeeding regeneration procedure in phosphorous drugged polysilicon passivation layers, located to be highly influenced by light strength and also temperature during annealing as well as light saturating stages.

While the systems behind it are still not fully recognized, the discovery can cause modifications in the commercial processes used in silicon PV cell production, as well as also supplies additional proof of the need to better understand the role of hydrogen in silicon cell chemistry.

Passivation layers play a vital role within a solar cell, protecting against corrosion as well as other reactions in between the cell products and also the ambient in which they will be made use of. Much less well comprehended are the long-term communications of the passivation layer itself with claimed atmosphere.

The ANU led team, which additionally included scientists from Chinese module giant JinkoSolar, investigated the lasting security of phosphorous doped silicon passivation layers in n-type silicon, lighting various samples at raised temperatures. With various examples they sought to check out the impact of different factors, including the passivation layer construction and also deposition process, firing profile and also the presence and properties of silicon nitride topping film.

Their observations and outcomes are released in the paper Long-term stability study of the passivation high quality of polysilicon-based passivation layers for silicon solar cells, published in Solar Energy Materials as well as Solar Cells.

Unexpected recuperation

The group discovered that the phosphorous drugged polysilicon get in touches with weakened throughout dark annealing as well as light soaking at temperatures, causing greater rates of recombination and also as a result lower cell efficiency. This sort of destruction is only observed on wafers that had actually undertaken a firing procedure, with non-fired wafers displaying steady passivation high quality.

The group was shocked to locate that under specific problems, examples would 'recuperate' from this deterioration, gaining back a lot of their initial efficiency. This healing procedure is still not totally understood, but is believed to be totally depending on the visibility of a silicon nitride capping layer (samples with this layer got rid of experienced considerably worse deterioration without any healing), as well as is also highly influenced by temperature and also light intensity.

The group recommends additional work to reveal the crucial role played by silicon nitride here, and also supposes that the visibility of hydrogen may likewise be a key aspect.