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本文首次运用Rothwarf的晶界复合损失模型及其修正因子分析和计算p—n结类型多晶Si太阳电池的光电流和短路电流。导出多晶Si少子有效寿命τ*和扩散长度L*与晶粒度和晶界表面态密度的关系式,根据多晶Si表面态密度的测量数据算出各晶粒度下的τ*和L*,并用它们计算多晶Si电池的二极管暗电流。在上述基础上进一步计算10μ和25μ厚的n+—p和n+—p—p+两种多晶Si太阳电池的效率,得到如下的主要结果和结论。 1.在大晶粒度下10μ和25μ厚电池的Jsc(或η)之间的差别显著,当晶粒度变小时,这种差别不断缩小,而当晶粒半径R=10μ时,无论是n+--p或n+—p—p+类型,两种厚度电池的Jsc(或η)之间的差别同时消失。值得注意的是,有关Jsc和η变化的上述特点也出现在Lanza等用数字计算法解连续方程所得的严格计算结果中。这说明我们采用的分析和计算方法也能象严格数字计算法那样较准确地反映和描述多晶Si太阳电池内部载流子的收集与复合情况,另一方面数字计算法本身难以为其结果中所出现的上述特点提供明确物理解释。而用晶界复合损失模型及其修正因子却能给以清晰地说明。这也许是本方法的优点之一。 2.发现我们计算的Jsc和η随晶粒度而增长的规律显著不同于Hovel的结果。Hovel的Jsc从R=O.1μ开始明显上升,并在尺=10μ达最大值(即单晶水平)。而我们的Jsc和η从尺>1μ开始明显上升,但直到R=500μ还未完全达到最大值。用巳有多晶Si电池在各晶粒度下的Jsc测量数据与上述两种计算结果和规律对照,发现我们的结果和规律更符合实际,因而可作出初步判断;即我们所采用的分析计算方法比Hovel的方法有更大的合理性。
For the first time, this paper uses Rothwarf’s grain boundary composite loss model and its correction factor to analyze and calculate the photocurrent and short-circuit current of p-n junction type polycrystalline Si solar cells. The relationship between the effective lifetime τ * and the diffusion length L * of the polycrystalline Si minority and the state density of the grain boundary and the grain boundary is deduced. According to the measurement data of the surface density of the polycrystalline Si, τ * and L * And use them to calculate the diode dark current for poly Si cells. Based on the above, we further calculated the efficiency of 10μ and 25μ thick n + -p and n + -p-p + polycrystalline Si solar cells, the following main results and conclusions. 1. The difference between the Jsc (or η) for 10μ and 25μ thick cells at large grain sizes is significant, and as the grain size becomes smaller, this difference continues to shrink. When the grain radius R = 10μ, n + -p or n + -p-p + type, the difference between Jsc (or η) for both thickness cells disappears at the same time. It is noteworthy that the above characteristics of Jsc and η changes also appear in the rigorous calculation results of Lanza and other numerical solution of continuous equations. This shows that the analysis and calculation methods we used also reflect and describe the collection and recombination of carriers within the polycrystalline Si solar cells more accurately than the strict numerical calculation method. On the other hand, The above mentioned features provide a clear physical explanation. However, the grain boundary composite loss model and its correction factor can give a clear explanation. This may be one of the advantages of this method. 2. We found that the law of Jsc and η that we calculated with the grain size is significantly different from that of Hovel. Hovel’s Jsc rises sharply from R = O.1μ and reaches a maximum (ie, single crystal level) at Ru = 10μ. Our Jsc and η increased significantly from 1 μ> but did not reach their maximum until R = 500 μ. Using the Jsc measurements of polycrystalline Si cells at each grain size against the above two calculations and laws, we found that our results and laws are more realistic and therefore make a preliminary judgment; that is, the analytical calculations we used The method is more reasonable than Hovel’s method.