MUNICH, Germany A manufacturing technique developed by Fraunhofer Institute ISE (Freiburg, Germany) helps to increase the energy yield of solar cells.
Fraunhofer researchers have displaced the contact pads for the solar cells in part from the frontside to the backside. The result is that the metalized area at the front side is reduced by almost 50 percent, Fraunhofer said. The area no longer needed for contact pads can then be used to generate more electricity.
The Metal Wrap Through (MWT) process requires three additional steps in the manufacturing process. First, laser holes have to be drilled through the solar cell. Then, in a screen print process, the contacts on the rear side are applied. At the same time, the vias are created; the screen print paste consists of a conducting material. Then, the contacts have to be coated with an insulator.
"The additional effort pays out", explained Ralf Preu, supervisor for production technology and quality assurance at Fraunhofer ISE. "In reducing the metalized area on the front side of the cell, the active area is increased und thus the current it yields," explained Preu.
First samples, manufactured on the institute's pilot production line, feature a current about 16 percent higher compared to conventional cells of the same size. Efficiency is some .5 percent points better than on standard solar cells made of the same polycrystalline material, the institute claims.
The researchers plan to present their system during the 22nd European Photovoltaic Solar Energy Conference in Milano, Italy, in September.