Reduction of light induced degradation by P-type c-Si wafer quality control in industrial PERC production

The impact of light induced degradation (LID) and wafer carrier lifetime have been measured on the basis of interstitial oxygen (Oi) concentration. The oxygen concentration in ingot is controlled by Argon flow rate, and the optimum carrier lifetime at low oxygen is investigated. These wafers are then processed in PERC mass production lines yielding average cell efficiency above 21.7%. The LID loss of 1% has been achieved after 40 hours with improved wafer quality having uniform base resistivity of 1Ω·cm and oxygen concentration below 16ppma(new ASTM, F121-83). Monitoring oxygen contents after annealing process from ingot growing to cell fabrication is the key aspect of quality control.