Effect of Phosphorus and Boron Diffusion Gettering on the Light Induced Degradation in Multicrystalline Silicon Wafers

Multicrystalline silicon (multi-Si) is currently the most widely used material for crystalline silicon solar cells. Although there has been substantial improvement in cell efficiency with the use of high-performance (HP) multi-Si, the PERC (passivated emitter and rear cell) devices fabricated from this material suffer from strong light-induced degradation (LID). This study aims to investigate the possibility of reducing LID in HP multi-Si wafers using diffusion gettering. By using inductively coupled plasma mass spectrometry, we measured the impurity concentration in sister samples subjected to different diffusion conditions. The results showed that a 50-Ω/sq POCl3 diffusion and 60-Ω/sq BBr3 diffusion at 800°C can getter impurities effectively. The interstitial Fe (Fei) and light-induced defect concentration was measured before and after gettering, using surface photovoltage measurements. After degrading the samples at 80°C for 24 hours, we observed that the light-induced defect concentration is lowest in HP multi-Si wafers that underwent phosphorus diffusion gettering. Samples subjected to boron diffusion gettering also show less LID compared to non-diffused sister samples.