The recent announcement by Trina Solar that it had reached a new solar conversion efficiency record of 24.13 percent in a Changzhou, China laboratory for an interdigitated back contact (IBC) mono-crystalline silicon cell, is a “significant achievement,” according to a U.S. laboratory analyst.
“The efficiency is significant given the size of the cell at six inches,” says Abasifreke Ebong, a professor in the Department of Electrical & Computer Engineering at the University of North Carolina at Charlotte.
The 156 millimeter (mm) ×156 mm solar cell reached a total-area efficiency of 24.13 percent as independently measured by the Japan Electrical Safety & Environment Technology Laboratories (JET).
Trina said that the n-type mono-crystalline silicon solar cell was fabricated on a large-sized phosphorous-doped Cz (cubic zirconia) Silicon substrate with a low-cost industrial IBC process, featuring conventional tube doping technologies and fully screen-printed metallization.
Ebong notes that “the process of fabricating the cell is not outlined, which I believe is still the expensive lithography technology. Also, it is a laboratory demonstration which may take another year or so to implement in production.” The Energy Production and Infrastructure Center (EPIC) at the Charlotte Research Institute campus of UNC Charlotte, is a state-of-the-art research center that conducts applied research.
The technical description of the cell test includes the following: “The champion cell presents the following characteristics: an open-circuit voltage Voc (overclocking) of 702.7mV (millivolt), a short-circuit current density Jsc (short-circuit current density abbreviation) of 42.1 mA/cm2 (milliamps per square centimeter) and a fill factor (FF) of 81.47 percent,” Trina reported.
In April 2016, Trina Solar announced an improved industrial low-cost IBC solar cell with a total-area efficiency of 23.5 percent. Total-area efficiencies are always lower than aperture-efficiencies, due to efficiency losses related to the edges of the cells and electrical contact areas.
In February 2014, Trina Solar and the Australian National University (ANU) jointly announced a world record aperture efficiency of 24.37 percent for a laboratory-scale 4.0 cm2 IBC solar cell, fabricated on a Float Zone (FZ) n-type substrate and using photolithography patterning. In December 2014, Trina Solar announced a 22.94 percent total-area efficiency for an industrial version, large size (156mm x 156mm, 6″ substrate) IBC solar cell, the company noted.
“Over the last few years, our R&D team has managed to continuously improve the efficiency of our n-type IBC solar cells, pushing the limits and surpassing our previous records, and approaching very closely to the performance of our best small-area laboratory cell developed in collaboration with ANU three years ago,” said Dr. Pierre Verlinden, Vice-President and Chief Scientist of Trina Solar.
“IBC solar cells are one of the most efficient silicon solar cells available today and are particularly suitable for applications for which the requirement of a high power density is more important than LCOE (Levelized Cost of Electricity). We are very happy to announce today that our industrial large area IBC cell has reached almost the same level of performance as the small-area laboratory cell made three years ago with a photolithography process,” Verlinden added.
Lead image: The 15-MW Sunshine Coast Solar Farm in Valdora powered by Trina Solar panels. Credit: Trina.