A conversion efficiency of 20.1% has been demonstrated by the collaboration between the Institute for Solar Energy Research in Hamelin (ISFH) and commercial partner SoLayTec on a monocrystalline boron-doped Czochralski p-type silicon wafer using a PERC-based solar cell.
ISFH noted that previously, a post deposition anneal (PDA) process step was required after the Al2O3 deposition process, increasing processing costs. However, developments have led PERC cell efficiencies as noted without a PDA step, lowering costs.
Dr. Dullweber, leader of ISFH’s solar cell production processes group said, “The optimized Al2O3 layer 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.”
Dr. Dullweber also noted that 21% efficiencies are achievable from recent device simulation work.
“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,” noted Roger Görtzen, manager marketing and sales and co-founder of SoLayTec. “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 Euro cents per wafer.”
The PV industry continues to face challenges in raising cell efficiencies cost effectively, slowing migration to volume production.