The Study Of Carrier Recombination For Silicon Solar Cells

Most of the photovoltaic market is dominated by crystalline silicon solar cell because of the high conversion efficiency compared to other solar cells. But high costs hinder the large scale application of crystalline silicon solar cells. With the development of manufacturing technique, the solar cell wafers will get more and more thin. However, with the reduction of wafer thickness, the surface recombination affects the lifetime of excess carriers seriously. Investigating the bulk and surface recombination behavior is great significance to improve the performance of crystalline silicon solar cells. The quasi-steady state photoconductance measurements are widely used to characterize the minority-carrier effective lifetime without destroying the sample morphology and contaminating samples.Firstly, in this thesis, based on the theory of excess carrier generation and recombination, the changing characteristics of bulk lifetime in monocrystalline silicon is analyzed under different injection levels. The mathematical model is established according to the one dimensional continuity equation and recombination theory of excess carriers. The surface recombination velocity and bulk lifetime are separated by using numerical method to solve the continuity equation under QSSPC measurement. Different dopant density wafers are investigated to extract the bulk time and SRV, we observe that bulk lifetime dependent upon carrier density influences the density distribution vitally rather than taking bulk lifetime as a constant at high injection level.Secondly, different filters are used to investigate the effects on N type monocrystalline silicon with different surface passivation and the distinction of the front and back surface recombination velocity. The n-type monocrystalline silicon effective lifetime with screen-printed aluminum paste is studied under different annealing temperature condition and find the optimal annealing temperature.