Longi Green Energy Technology has announced a new world record for silicon solar cell efficiency, achieving 28.13% with its hybrid interdigitated-back-contact, or HIBC, solar cell.
The result came only hours after Trina Solar said it had reached 28.0% efficiency with its TOPCon-compatible hybrid back-contact solar cell technology.
Longi said the new result was independently verified by the Institute for Solar Energy Research Hamelin, also known as ISFH.
The company added that HIBC-based solar modules with 26.4% efficiency were certified by the National Renewable Energy Laboratory, or NREL. Longi said these advances in technology have already created an advantage in mass production.
Longi previously outlined details of its HIBC architecture in a scientific paper published in November. According to the company, the design combines passivated tunneling contacts, dielectric passivation layers, and both n-type and p-type contacts.
The solar cell is built on a high-resistivity half-cut M10 wafer with edge passivation and optimized n-type contacts produced through a combined high- and low-temperature process.
An indium tin oxide layer is used to improve lateral transport, while multilayer aluminum oxide and silicon nitride coatings help reduce surface recombination losses.
Longi said it reduced phosphorus doping in the n-type polycrystalline silicon layer to limit dopant diffusion into the wafer.
The company’s in situ passivated edge process enables edge passivation during fabrication.
It also uses deep-trenched metal fingers and selective indium tin oxide etching to reduce leakage between n-type and p-type contacts. A thicker amorphous silicon layer is used to improve junction coverage and sidewall encapsulation.
To lower contact resistivity without affecting passivation, the amorphous silicon layer is crystallized using a pulsed green nanosecond laser.
Longi said the technology could be scaled for heterojunction solar cell manufacturing.
However, the company added that further improvements are still needed to reduce resistive losses in the p-type contact.
