Highly improved passivation of PECVD p-type TOPCon by suppressing plasma-oxidation ion-bombardment-induced damages

• Published in: Solar energy Vol. 242; pp. 1 - 9
• Main Authors: Ma, Dian, Liu, Wei, Xiao, Mingjing, Yang, Zhenhai, Liu, Zunke, Liao, Mingdun, Han, Qingling, Cheng, Hao, Xing, Haiyang, Ding, Zetao, Yan, Baojie, Wang, Yude, Zeng, Yuheng, Ye, Jichun
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.08.2022
• Subjects: Ion-bombardment; Passivation; PECVD p-type TOPCon; Plasma-assist oxidation; Plasma-assist oxidation; PECVD p-type TOPCon; Ion-bombardment; Passivation
• ISSN: 0038-092X; 1471-1257
• DOI: 10.1016/j.solener.2022.07.003

•Two-step oxidation (TSO) was effective in suppressing the ion-bombardment damage.•PECVD p-TOPCon with TSO SiOx shows excellent passivation with an iVoc of ∼712 mV and a J0,s of ∼10 fA/cm2.•P-TOPCon with TSO SiOx produces a low contact resistivity of ∼10 mΩ·cm2.•An efficiency of 24.6% based on the state-of-the-art technology is predicted by numerical simulations. Tunnel oxide passivated contact (TOPCon) integrated with a plasma-enhanced chemical vapor deposition (PECVD) boron-doped polysilicon has the potential to achieve high-efficiency and low-cost solar cells. In this contribution, we explore the feasibility of using PECVD technology to prepare high-performance p-type TOPCon (p-TOPCon) by growing two-step oxidation (TSO), i.e., a nitric acid oxidation (NAOS) SiOx without ion-bombardment followed by a plasma-assist N2O oxidation (PANO) SiOx layer. The experimental results reveal that for p-TOPCon structures on polished wafers with the conventional plasma oxidation SiOx, raising plasma oxidation powers to increase the thickness and oxidation degree of SiOx cannot ensure high-quality passivation due to the appearance of high-density defects caused by plasma ion-bombardment. In the presence of an additional NAOS SiOx layer, ion-bombardment-induced defects can be effectively suppressed, leading to a remarkable improvement in passivation properties. In detail, the optimal p-TOPCon with TSO SiOx achieves a maximum implied open-circuit voltage (iVoc) of ∼712 mV and a minimum single-sided saturation current density (J0,s) of ∼10 fA/cm2, manifesting an increment of iVoc by ∼10 mV, and a reduction of J0,s by ∼5 fA/cm2. Finally, the numerical simulations reveal that n-type Si solar cells featuring p-TOPCon rear junction and Al electrode could receive an efficiency of 24.6% based on the state-of-the-art device fabrication technology. In general, this work provides a new way to boost the passivation quality of PECVD p-TOPCon devices.