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A Chinese analysis group has developed a novel thin-silicon wafer strengthened ring (TSRR) to guard ultra-thin wafers and photo voltaic cells throughout manufacturing. This method consists of making use of the ring on the sting of skinny wafers and is appropriate with all silicon photo voltaic module expertise.
A analysis group from China’s Shanghai Jiao Tong University and Sun Yat-sen University has proven that using a novel thin-silicon wafer strengthened ring (TSRR) alongside the sting of skinny wafers allows the PV materials to which is much less susceptible to breakage. TSRR has been demonstrated on silicon wafers with a thickness of 4.7 μm, photo voltaic cells with a thickness of 28 μm, and bigger wafers with a thickness of 60 μm.
“Our group has developed a brand new method appropriate with industrial manufacturing processes to make use of ultrathin crystalline silicon wafers which can be lower than 60 μm, and will be as skinny as 20 μm. The expertise makes the cells which is much less brittle”, researcher Taojian Wu mentioned pv journal.
“We had been shocked {that a} 4-in [100 mm] wafer with a thickness of lower than 5 µm will be obtained by a easy strengthened ring technique, and that we will simply put together 28 µm silicon photo voltaic cells with an effectivity of greater than 20% by way of this technique,” Wu mentioned, including delicate enhancements. of the “construction of skinny silicon” led to such “nice progress.”
In the analysis, the group first ready a free-standing 4.7 μm thick 4-inch (100 mm) wafer utilizing TSRR. It then produced dopant-free 28-μm silicon cells with interdigitated again contacts (IBC) utilizing TSRR, leading to a breakage charge of almost 0%. The cell effectivity achieved is 20.33%, which is licensed at 20.05%.
This is the best effectivity reported for silicon photo voltaic cells with a thickness of lower than 35 μm, in line with greater than a decade of literature efficiency knowledge collected by the group.
The researchers famous that the TSRR technique requires solely three extra manufacturing steps than typical PV mass manufacturing processing. It first deposits a 70 nm silicon nitride (SiNx) layer on each side of conventionally thick silicon wafers by plasma-enhanced chemical vapor deposition (PECVD) or low-pressure chemical vapor deposition (LPCVD), then the SiNx is faraway from the central area on one facet utilizing a die, laser, or photolithography, to create a gap, and adopted by an alkaline answer etching step to the specified thickness, in line with the group.
The SiNx layer supplies safety and allows the silicon within the facet area of the wafer to take care of its unique thickness, the analysis group defined. “The troublesome half is the method of depositing a high-quality SiNx protecting movie, which should be capable of face up to long-term etching in an alkaline answer,” mentioned Wu. “The straightforward half is the manufacturing means of skinny silicon photo voltaic cells as a result of we will course of skinny silicon wafers with strengthened rings in the identical method as we course of regular wafers of silicon.”
The group acknowledged that the TSRR construction can be utilized with “any silicon expertise”, similar to passivated emitter and rear cell (PERC), silicon heterojunction (SHJ), tunnel oxide passivating contact (TOPCon), in addition to dopant-free passivating contact xBC cell expertise.
To higher perceive the optoelectrical efficiency of experimental photo voltaic cells, the group performed a TCAD numerical simulation of back and front contacts (FBC) photo voltaic cells. Experiments and simulations of mechanical properties evaluating TSRR and traditional skinny silicon constructions show to help the function of TSRR, in line with the analysis group.
The group additionally ready 50 μm to 60 μm textured TSRR wafers, measuring 182 mm × 182 mm, and carried out key manufacturing processes to substantiate the economic suitability of the TSRR technique. “We have obtained suggestions from our accomplice firm that the breakage charge throughout the manufacturing of 60 μm-SHJ photo voltaic cells has been considerably lowered,” mentioned Wu.
The analysis is detailed in “Free-standing ultrathin silicon wafers and photo voltaic cells by edges reinforcement,” revealed in environmental communication.
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