Spatially resolved photocurrent measurements of organic solar cells: tracking water ingress at edges and pinholes
Spatially resolved photocurrent measurements of organic solar cells: tracking water ingress at edges and pinholes
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DOI：
10.1016/j.solmat.2012.10.027
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发表时间：
2013-02
影响因子：
6.9
通讯作者：
Krishna Feron;T. Nagle;L. Rozanski;Bill Gong;C. Fell
中科院分区：
文献类型：
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作者：
Krishna Feron;T. Nagle;L. Rozanski;Bill Gong;C. Fell
有机太阳能电池中的许多降解机制都是由某些点的水进入所支撑的。我们演示了使用光电流映射技术来检查在电池边缘和阴极层针孔处的水的扩散进入。用扩散模型计算得到水在聚(3，4-乙二氧基噻吩基)：聚苯磺酸层中的扩散系数为(5.0±2.7)×10−6cm2s−1。这一层的存在使细胞的降解率增加了十倍。关于水的哪种进入途径是最重要的，文献中没有定论。我们发现：(A)水的进入明显地发生在针孔和器件边缘，而不是均匀地通过阴极膜；(B)在针孔的入射与在边缘的入射具有相同的时间依赖性，但绝对速率取决于针孔的大小；以及(C)在器件边缘的退化甚至比在较大的针孔更快，除非阴极层延伸到有源电池的边界之外。由此可见，电池的横向结构会显著影响器件效率的降低，我们对这种影响进行了量化。我们证明，光电流映射方法不需要为了跟踪水的进入而完全地局部湮灭器件性能，这意味着该方法对于研究商业或接近商业的器件中通过封装剂的水进入也是有价值的。
Many degradation mechanisms in organic solar cells are underpinned by the ingress of water at certain points. We demonstrate the use of a photocurrent mapping technique to examine the diffusive ingress of water at the edges of a cell and at pinholes in the cathode layer. A diffusion model applied to the experimental results leads to a value of (5.0±2.7)×10−6cm2s−1for the diffusivity of water in the poly(3,4-ethylenedioxythiophene):poly(styrene sulphonate) layer. The existence of this layer increases the rate of cell degradation by a factor of ten. The literature is inconclusive with respect to which entry pathway for water is the most important. We find that (a) water ingress clearly occurs at pinholes and at the device edges, rather than uniformly through the cathode film; (b) that ingress at pinholes has the same time dependence as ingress at the edges, however the absolute rate depends on the size of the pinhole; and (c) that degradation at the device edges is faster than even at larger pinholes, except where the cathode layer extends beyond the boundary of the active cell. It follows that the lateral architecture of the cell can significantly impact the degradation of efficiency in the device, and we quantify this effect. We demonstrate that the photocurrent mapping method does not require complete local annihilation of device performance in order to track the ingress of water, which means that the method may also be valuable for the study of water ingress through encapsulants in commercial or near-commercial devices.