Investigation On Passivation Of Crystalline Silicon And Light Induced Degradation Effect Of Crystalline Silicon Solar Cells

In recent ten years, photovotaic industry has been developing rapidly, in which the crystalline silicon solar cells not only have a substantial reduction in cost, but also have a great enhancement in conversion efficiency, which has improved from 17% to 20%. A variety of efficient structure of the solar cell also has a great breakthrough. As the key technology which influences the efficiency of crystalline silicon solar cell, the problem of the passivation of p-type crystalline silicon surface and the light induced degradation(LID) effect in crystalline silicon cells has not been well solved. In this paper, these two issues have been studied.In this thesis we prepared SiNx and Al2O3 films by PECVD and ALD deposition technique. And we studied the effects of heat treatment, annealing temperature and film thickness on the surface passivation through RTP treatment. At the same time, the fixed charge density of the passive film and the interface defect density of the passive film were characterized by PV2000 A test system.In addition, the LID effect of the boron doped crystalline silicon cell was verified by the experimental results of the minority carrier lifetime samples and solar cells. It was found that the electrical properties such as open circuit voltage, short circuit current and conversion efficiency have degraded obviously. The efficiency of the conventional sc-Si PERC cell degraded 3% after illuminated for 1710 min, and degradation of the sc-Si PERC cell efficiency is 4.25%. It is considered that the formation of the phenomenon of the LID effect includes the following three points:(1) The formation of B-O complex, which has a serious effect on the carrier.(2) The defects related to the gap Fe also cause the light induced degradation.(3) The interface defect density of the passivation layer has a certain increase. So that the fading of passivation effect of the passivation layer is another influencing factor of the LID effect.Finally we prepared the solar cells which could effectively suppress the light induced degradation by using gallium doped silicon instead of the ordinary boron doped crystalline silicon.The degradation rate of the single crystal silicon PERC cell and the polycrystalline cell reduced to0.91% and 0.68% respectively. At the same time, we studied the regeneration effect of crystalline silicon, and the experimental results showed that the light induced degradation of crystalline silicon cells could be effectively inhibited by the regeneration treatment. It was found that the efficiency decay ratio of all the cells was lower than 1% after illumination for 1710 min, and the optimal conditions for the regeneration treatment was 200? for 10 min for illumination in air.