Researchers from Germany’s research center Helmholtz Zentrum Berlin (HZB) have found the reason why holes in perovskite films produced through a spin coating technique and used in solar cells do not cause a reduction in the cells’ performance.

HZB team shows why holes do not always harm efficiency image

The team said that these holes, which are commonly responsible for leading to short circuits in the solar cell by the adjacent layers of the solar cell coming into contact, if produced through a spin coating technique, do not lead to significant short circuits between the front and back contact of the cell, and so do not negatively impact the cell’s performance.

The research group used scanning electron microscopy to observe the perovskite films used in the research, and discovered that the solar cells do not see their performance degrade thanks to a high-rate charge carrier recombination.

“We were able to show that the substrate was not really exposed even in the holes, but instead a thin layer is being built up essentially as a result of the deposition and crystallization processes there that apparently prevents short circuits,” the scientists said.

“The electron transport layer (TiO2) and the transport material for positive charge carriers (Spiro MeOTAD) do not actually come into direct contact. In addition, the recombination barrier between the contact layers is sufficiently high that the losses in these solar cells is minute, despite the many holes in the perovskite thin-film,” added research coordinator Marcus Bär.