Growth of 300 mm n-type recharged Czochralski silicon crystal with low oxygen content by dual side-heaters

With the rapid progressing of global photovoltaics (PV) industry, the performance of Czochralski silicon (Cz-Si) solar cells continues to improve, which puts forward higher requirements for the quality of Cz-Si crystals. In particular, interstitial oxygen concentration of 300 mm n-type Cz-Si wafers for Tunnel Oxide Passivating Contact (TOPCon) solar cells needs to be further reduced to avoid possible oxygen-related defects caused by high-temperature processing such as boron diffusion-in. For this purpose, this study further optimized the configuration of the proposed heating zone structure with dual side-heaters for 300 mm n-type recharged Cz-Si crystal growth, combined with numerical simulations and on-site experiments, revealing the influence of heating zone structure on the temperature distribution of silicon melt and interstitial oxygen concentration in Cz-Si crystal. Consequently, the growth of champion-grade 300 mm n-type recharged Cz-Si crystals with interstitial oxygen concentration below 8 ppm with the lowest value below 5 ppm can be realized. In addition, electrical performance of n-type TOPCon solar cells based on the 300 mm n-type Cz-Si wafers with the interstitial oxygen concentration lower than 10 ppma have presented excellent electrical performance and lower defect ratio, which also demonstrates the effectiveness of the proposed heating zone structure for the growth of 300 mm n-type recharged Cz-Si crystals.