导纳谱应用于铜铟镓硒中缺陷的能量分布

Characterization of the energy distribution of defects in CIGSe solar cell by admittance spectroscopy

摘要:

该文通过导纳谱技术表征铜铟镓硒(CIGSe)太阳电池吸收层中缺陷的能量分布研究了退火前后铜铟镓硒(CIGSe)太阳电池退火后效率提高的机理。我们发现退火后铜铟镓硒(CIGSe)电池的暗电流下降了大约一个数量级，电池的理想因子也从2.16下降到1.85。在反向偏压下，退火前铜铟镓硒(CIGSe)太阳能电池的电容高于退火后太阳能电池的电容。通过对于电池的C-V特性作1/C2 vs. V线性拟合发现退火前铜铟镓硒电池吸收层中的自由载流子浓度高于退火后。我们通过1/C2 vs. V线性拟合后获得退火前电池的内建电场分别为0.52 V和0.64 V。通过导纳谱表征，退火后吸收层中缺陷的激活能降低，但是缺陷浓度几乎不变。缺陷激活能的降低意味着铜铟镓硒太阳能电池中缺陷的Shockley-Read-Hall (SRH)复合概率降低，因此退火后太阳能电池的开路电压和并联电阻都有一定的提升幅度。

Abstract:

In this work, we used admittance spectroscopy to accurately characterize the defect energy distribution of defects in the absorption layer of a CuIn1-xGaxSe2 (CIGSe) solar cell. We found that the dark current of the CIGSe cell decreased by an order of magnitude and its ideality factor dropped from 2.16 to 1.85 after annealing. The capacitance of the CIGSe solar cell before annealing was higher than that after annealing under reverse bias. Moreover, a higher free carrier concentration was found in the absorption layer of the cell before annealing. The results of our tests show that the built-in electric voltages of the CIGSe cell before and after annealing were 0.52 V and 0.64 V respectively. After annealing, the activation energy of defects in the absorption layer decreased and their concentration remained almost constant, as measured by admittance spectroscopy. The decrease of the defect activation energy indicated a corresponding decrease in the Shockley–Read–Hall recombination probability of defects in present cell, hence the increase of the open circuit voltage and parallel resistance of the CIGSe solar cells after annealing resulted in improved performance.