IEEE PVSC 49
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SPLTRAK Abstract Submission
Novel Laser Oxidation for Screen-Printed Selective Area Front Poly-Silicon Contacts for TOPCon Cells
Sagnik Dasgupta1, Young-Woo Ok1, Vijaykumar D. Upadhyaya1, Wook-Jin Choi1, Ying-Yuan Huang3, Shubham Duttagupta2, Ajeet Rohatgi1
1Georgia Institute of Technology, Atlanta, GA, United States
/2Solar Energy Research Institute of Singapore, Singapore, Singapore
/3National Yang Ming Chiao Tung University, Tainan City, Taiwan

The efficiency potential of
double-side tunnel oxide passivated contact (DS-TOPCon) solar cells is limited by parasitic absorption in the front poly-Si layer, despite excellent passivation and high VOC. The use of patterned poly-Si only under the front metal grid lines can significantly reduce the parasitic absorption loss without sacrificing voltage. In this work, we demonstrate a simple, manufacturing-friendly method of patterning the front poly-Si using a nanosecond UV (355 nm) laser. We found that with laser powers ≥3 W at a 400 mm/s scan speed, a 1-4 nm thick stoichiometric SiO2 layer was grown on TOPCon. This served as a mask for KOH-etching of 200 nm poly-Si, allowing for patterning of poly-Si fingers required for selective TOPCon. While laser powers above 3 W caused substantial deterioration in passivation quality, the resulting damage in J0 was largely recovered by subsequent PECVD SiNx deposition. At 3 W, the full area J0 was found to be 36.8 fA.cm-2. This translates to 1.68 fA.cm-2 for 4.48% coverage from the wing area of the poly-finger lines (100 lines-100 𝜇𝑚 wide, 30 𝜇𝑚 metal) contributing to a total front J0 of ~10 fA.cm-2, well suited for 25% efficient solar cells.