Effect On Effective Minority Carrier Lifetime Of Cz Si Wafer And Solar Cells By SiO₂ Layer And P-Al Gettering

Surface passivation technology due to existence of dangling bonds has become the key issues for mass production of crystalline silicon solar cells, and plays key role in improvement of open circuit voltage (Voc) and short circuit current (Isc) of solar cells. It is well committed that efficiencies of solar cell over 20% in PV field can be achieved with surface passivation technology unexceptionally, improving greatly in effective minority carrier lifetime, and achieving higher Voc and Isc. In the process of crystalline silicon growth and solar cell fabrication, some metal impurities (Na,Fe,Cu and Au) can be introduced into material. The metal impurities together with defects in semiconductor generated deep levels, which was turn into recombination centers of minority carrier, degrading lifetime, diffusion length and efficiency of solar cells. How to eliminate effect on solar cells for surface dangling bonds and metal impurities is one of main research subjects nowadays.The purpose of the paper is SiO2 layer by several thermal oxidation passivated surface state of CZ Si and P-Al gettered effectively in solar cells, improving effective lifetime and efficiency of solar cells.In this paper, surface passivation was investigated by Classical Thermal Oxidation (CTO), Rapid Thermal Oxidation (RTO) and TCA, and P-Al gettering was introduced into mc-Si solar cells. Minority carrier lifetime, thickness and refractive index of layer of post-processing samples were respectively measured by micro-waves State Photoconductance Decay (μ-PCD) , and got an optimal technology process of surface passivation and gettering.On the base of experimental results, we can get a conclusion that all samples can reach high minority carrier lifetime by CTO, TCA and RTO. SiO2 layer growth rate is relatively rapid and decompound temperature is relatively high by TCA, which degrade lifetime of samples in a way. Consequently, if we can seek for a reagent contained Cl and of which decompound temperature is relatively low, combining with RTO method, it will be a good choice for surface passivation technology of will-be solar cell industry. By the research on P, Al and P-Al co-gettering, we can observe that minority carrier lifetime and conversion efficiency of samples improve greatly by the three gettering methods, and combination of P and Al gettering is the most effective way.