Investigating the Influence of Interfacial Contact Properties on Open Circuit Voltages in Organic Photovoltaic Performance: Work Function Versus Selectivity
Investigating the Influence of Interfacial Contact Properties on Open Circuit Voltages in Organic Photovoltaic Performance: Work Function Versus Selectivity
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DOI：
10.1002/aenm.201200669
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发表时间：
2013-05-01
影响因子：
27.8
通讯作者：
Olson, Dana C.
中科院分区：
文献类型：
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作者：
Ratcliff, Erin L.;Garcia, Andres;Olson, Dana C.
研究了聚(n -9-庚烷-2,7-咔唑-醛-5,5-（4,7-二-2-噻基-2,1,3-苯并噻唑）（PCDTBT）和[6,6]-苯基- c71丁酸甲酯（PC71BM）太阳能电池中空穴收集触点的功函数和热力学选择性对开路电压（VOC）来源的影响。在没有电荷选择性、电子阻断接触的情况下，接触功函数的系统变化直接决定了VOC（由空穴和电子的相对费米能级之间的能量分离所定义），而观察到的暗饱和电流J0几乎没有变化。通过增加对共混物中富勒烯向空穴触点注入电子的阻挡，提高了触点的电荷选择性，从而降低了反向饱和电流（降低了J0，增加了分流电阻RSH），提高了VOC。基于这些观察结果，我们提供了一套触点设计标准，用于调整大块异质结有机光伏电池中的VOC。
The role of work function and thermodynamic selectivity of hole collecting contacts on the origin of open circuit voltage (VOC) in bulk heterojunction organic photovoltaics is examined for poly(N-9-heptadecanyl-2,7-carbazole-alt-5,5-(4,7-di-2-thienyl-2,1,3-benzothiadiazole) (PCDTBT) and [6,6]-phenyl-C71 butyric acid methyl ester (PC71BM) solar cells. In the absence of a charge selective, electron blocking contact, systematic variation of the work function of the contact directly dictates the VOC, as defined by the energetic separation between the relative Fermi levels for holes and electrons, with little change in the observed dark saturation current, J0. Improving the charge selectivity of the contact through an increased barrier to electron injection from the fullerene in the blend into the hole contact results in a decreased reverse saturation current (decreased J0 and increased shunt resistance, RSH) and improved VOC. Based on these observations, we provide a set of contact design criteria for tuning the VOC in bulk heterojunction organic photovoltaics.