The distribution of the inner electric field in organic solar cells studied by electroabsorption spectroscopy

研究了以下三种有机太阳电池的内部电场与光电流的关系，以找出产生光电流的机理：1.锌酞菁(ZnPc)肖特基势垒太阳电池；2.锌酞菁(ZnPc)/茂金属化合物(PTCBI)异质结太阳电池；3.锌酞菁(ZnPc)/C_(60)；异质结太阳电池.结果表明，激子的解离或载流子的产生是由内电场引起的.特别是在异质结的情况下，内部电场是产生电荷的最重要的驱动力，尽管许多研究人员认为电荷产生是由于异质结中两个有机半导体的电子亲和势不同造成的。研究还发现，在Au/ZnPc界面处出现了一种反常现象，称为带滑移，它影响了电池的内部电场分布和光伏特性。对于ZnPc肖特基势垒太阳电池，在反向偏置条件下，内部电场服从通常的耗尽层理论，而在正向偏置条件下，内部电场被ZnPc与电极之间的带滑移所猝灭。在ZnPc/PTCBI异质结的情况下，PTCBI层的内部电场与偏置电压无关，也与光电流无关。这种内部电场不是PTCBI薄膜中的体电场，而是PTCBI与In电极界面处的反常电场。在ZnPc/C&t；60&gt；异质结的情况下，检测到C&lt；60&gt；层中的体电场。对于ZnPc层和C&lt；60&gt；层，内电场与光电流之间都有很好的相关性，说明载流子是由内电场产生的。

The correlation between the inner electric field and the photocurrent was studied for the following three types of organic solar cells, in order to find the mechanism of the photocurrent generation.1.Zn-phthalocyanine(ZnPc) Schottky-barrier solar cells2.Zn-phthalocyanine(ZnPc)/Perylene derivative(PTCBI) heterojunction solar cells3.Zn-phthalocyanine(ZnPc)/C_<60> heterojunction solar cellsAn obtained result is that the dissociation of the excitons, or the carrier generation is caused by the inner electric field. Especially, in the cases of the heterojunctions, the inner electric field is the most important driving force for the charge generation, although many researchers believe that the charge generation is caused by the difference in the electron affinities of the two organic semiconductors in a heterojunction. It has also be found that an anomaly, which we call band slipping, occurs at Au/ZnPc interface, which affects the distribution of the inner electric field and the photovoltaic properties.In the case of the ZnPc Schottky-barrier solar cells, the inner electric field obeys the usual theory of depletion layer for the reverse bias condition, but for the forward bias, the inner electric field is quenched by the band slipping between ZnPc and the electrode. In the case of the ZnPc/PTCBI heterojunctions, the inner electric field of the PTCBI layer is independent of the bias voltage and has no correlation with the photocurrent. This inner electric field is not the bulk field in the PTCBI film but is an anomalous field at the interface between PTCBI and In electrode. In the case of ZnPc/C_<60> heterojunctions, the bulk electric field in the C_<60> layer was detected. Both for the ZnPc and C_<60> layers, very good correlation was observed between the inner electric field and the photocurrent, indicating that the carriers are generated by the inner electric filed.