Influence of the indium tin oxide/organic interface on open-circuit voltage, recombination, and cell degradation in organic small-molecule solar cells
Influence of the indium tin oxide/organic interface on open-circuit voltage, recombination, and cell degradation in organic small-molecule solar cells
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DOI：
10.1103/physrevb.83.165311
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发表时间：
2011-04
影响因子：
3.7
通讯作者：
S. Schäfer;A. Petersen;T. Wagner;R. Kniprath;D. Lingenfelser;Achmad Zen;T. Kirchartz;B. Zimmermann-B.-Z
中科院分区：
文献类型：
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作者：
S. Schäfer;A. Petersen;T. Wagner;R. Kniprath;D. Lingenfelser;Achmad Zen;T. Kirchartz;B. Zimmermann-B.-Z
本文研究了小分子有机太阳能电池在氧化铟锡(ITO)/有机界面上的性能和稳定性。比较和测试了经ITO O2等离子体处理前后不同结构的锌酞菁/富勒烯(C60)电池在惰性气氛中光照下的降解行为。光电子能谱(UPS和XPS)表明，O2等离子体处理使ITO功函数从4.3 eV提高到5.6 eV。我们发现，ITO功函数的增加以及在ITO和施主/受主混合层之间引入电子阻挡层都使开路电压VOC增加了200 mV以上。对于这两种情况，我们的连续体法器件模拟定量地将VOC的增加与接触复合的减少以及暗电流的减少联系起来。对于建立在臭氧处理的ITO上的细胞，我们发现AM 1.5光谱的紫外线部分导致了细胞的快速降解。我们将这种退化，表现为VOC降低了25%，这是血浆诱导的ITO功函数增加的部分逆转。此外，我们还证明，细胞结构的改变可以减少降解，从而提高细胞的稳定性。我们对ITO/有机界面复合及其对开路电压和电池稳定性的影响进行了全面的研究。
In this paper we investigate the performance and stability of small-molecule organic solar cells with respect to the indium tin oxide (ITO)/organic interface. Different zinc-phthalocyanine (ZnPc)/fullerene (C60) cell architectures with and without ITO O2-plasma treatment are compared and tested with respect to their degradation behavior under illumination in inert atmosphere. Photoelectron spectroscopy (UPS and XPS) shows that the O2-plasma treatment increases the ITO work function from 4.3 eV up to 5.6 eV. We find that both the increased ITO work function as well as the introduction of an electron blocking layer between ITO and the mixed donor/acceptor layer increases the open-circuit voltage Voc by more than 200 mV. For both cases our continuum approach device simulation quantitatively relates the increase of Voc to a reduced contact recombination and thus a reduced dark current. For cells built on ozone treated ITO we find a fast cell degradation caused by the UV part of the AM 1.5 spectrum. We identify the degradation, which manifests itself in a decrease of Voc of up to 25%, as a partial reversion of the plasma induced ITO work function increase. Additionally, we demonstrate that the degradation can be reduced by structural changes in the cell architecture, leading to improved cell stability. We present a comprehensive study of the recombination at the ITO/organic interface and its influence on the open-circuit voltage and the cell stability.