Two companies partnered across the Atlantic to create highly efficient silicon solar cells made with kerfless wafers. Together imec and Crystal Solar have created a 22.5 percent efficient photovoltaic solar cell on a kerfless (low-waste) silicon wafer. Since their technology reduces waste in the PV manufacturing process it can further reduce the costs of solar power.
"This approach represents a new paradigm in cell manufacturing with its unique ability to bypass significant steps in both wafer and cell manufacturing thereby dramatically reducing the capex and the overall cost per watt,” said T.S. Ravi, CEO of Crystal Solar. “We expect to achieve >23 percent efficiencies with IMEC's PERT technology in the very near future,” he added.
Kerfless wafering might not sound too interesting but researchers have been looking to it as a more efficient way to produce crystalline silicon solar cells for a while. Traditionally silicon cells are made by cutting through a silicon ingot with a wire saw to to produce the wafer that the PV components are placed on. The cuts from the wire saw produce waste called kerf.
Kerfless wafers generally use an implant and cleave process or stress liftoff method to produce wafers from the large chunk of silicon. The first forces ions into a subsurface layer of the ingot, allowing a wafer to be cleaved off. The second, stress liftoff separates the silicon where the silicon interfaces with a deposited layer of thin film. Thus far neither have been made commercially efficient or able to produce high-quality wafers. But the new devices from the joint venture show good promise.
The wafers are epitaxially grown so that the crystals are grown on substrate that mimics the orientation of the substrate. Crystal Solar converts feedstock gas to mono crystalline silicon wafers with its Direct Gas to Wafer technology. By creating the wafer directly from a gas it skips processes that add complexity, cost and energy use. “Imec has adapted its highly efficient nPERT Si solar cell process to align with the properties of Crystal Solar's kerfless wafers,’ the companies said.
“By skipping the polysilicon, ingoting and the wire-sawing steps altogether, this approach not only results in lowest cost/watt for the wafers but also significantly reduces the capital required to set up a manufacturing plant. Furthermore, this process enables the growth of high quality p-n junctions in-situ which reduces cell making steps while increasing the efficiency,” the companies said. They contended that it’s a first for the industry and the high efficiency could lead to industrialization of the technology.
"The combination of our advanced cell process and the innovative wafer manufacturing technique of Crystal Solar, is paving the way for manufacturing of highly efficient solar cells at substantially lower cost and will be disruptive for the complete solar manufacturing value chain,” said Jozef Szlufcik, imec PV department director.Tweet