SoLayTec and ISFH announce efficiency improvement for PERC solar cell
ISFH and SoLayTec have achieved a conversion efficiency of 20.1% applying a 5nm thin spatial ALD Al2O3 layer as rear passivation of industrial-type PERC solar cells.
So far, the spatial ALD process involved a Post Deposition Anneal (PDA) after the Al2O3 eposition. However, now ISFH and SoLayTec have proven that >20% PERC cells can be made without any additional PDA process.
SoLayTec installed in May 2012 an InPassion LAB tool at their research partner Institute for Solar Energy Research in Hamelin (ISFH), funded by the German Ministry for the Environment, Nature Conservation and Nuclear Safety, and since then ISFH has optimized the Al2O3 ayer which is deposited in the spatial ALD (atomic layer deposition) tool.
"The optimized Al2O3 ayer has been applied with a SiN capping layer as rear passivation stack to ISFH's industrial-type passivated emitter and rear cells (PERC). The PERC cell processing includes a homogeneously POCl3-diffused emitter, screen-printed front and rear metal contacts and uses industry-standard 156x156mm2 mono-crystalline boron-doped Czochralski p-type silicon wafers." Comment by Dr. Dullweber, leader of ISFH's solar cell production processes group. "Our advanced device simulations show that efficiencies up to 21% will be achievable in short term using an industrial PERC cell process in combination with the ultrathin Al2O3 rear passivation layers deposited by means of spatial ALD" comments Prof. Dr. Jan Schmidt, who is the Head of the Photovoltaic Department of ISFH.
"This will enable the PV market to lower the costs for implementing Al2O3 on two aspects. Firstly, as no additional PDA process is needed, the costs for an additional PDA furnace can be saved. Secondly, the excellent quality of SoLayTec's Al2O3 allows outstanding chemical and fixed charge passivation already at 5 nm Al2O3 layer thickness compared to 20 to 25 nm required with a PECVD system. This means with mass production InPassion ALD from SoLayTec, the customer can reach costs for Al2O3 layers below 2 €ct per wafer." Comment by ing. Roger Görtzen, manager marketing and sales and co-founder of SoLayTec.
