Direct observation of UV-induced charge accumulation in inverted-type polymer solar cells with a TiOx layer: Microscopic elucidation of the light-soaking phenomenon
Direct observation of UV-induced charge accumulation in inverted-type polymer solar cells with a TiOx layer: Microscopic elucidation of the light-soaking phenomenon
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DOI：
10.1063/1.4963285
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发表时间：
2016-09
影响因子：
4
通讯作者：
D. Son;T. Kuwabara;Kohshin Takahashi;K. Marumoto
中科院分区：
文献类型：
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作者：
D. Son;T. Kuwabara;Kohshin Takahashi;K. Marumoto
用电子自旋共振(ESR)研究了结构为InTiOx/TiOx/P3HT：PCBM/Au的倒置型有机太阳能电池(IOSCs)的浸光机理。用ESR观察到紫外光照射过程中细胞内的电荷积累，这与光浸泡现象有明显的相关性。电荷积累的原因被阐明为在TiOx层的能带激发下，空穴转移后与溴一起被深陷于p型P3HT聚合物链端的空穴。在能带激发后，空穴被认为是被TiOx层中的俘获电子所吸引。这些累积的电荷是浸光现象的根源。我们的结果强烈地表明，需要钝化TiOx层中剩余的OH基团，以防止电子陷阱来避免光吸收现象，这一步骤对于在没有紫外光照射的情况下运行高稳定的IOSCs是必不可少的。
The mechanism of light-soaking phenomenon in inverted-type organic solar cells (IOSCs) with a structure of indium-tin-oxide/TiOx/P3HT:PCBM/Au was studied by electron spin resonance (ESR) spectroscopy. Charge accumulation in the cell during UV-light irradiation was observed using ESR, which was clearly correlated with the light-soaking phenomenon. The origin of the charge accumulation is clarified as holes that are deeply trapped at p-type P3HT polymer-chain ends with bromine after hole transfer from the band excitation in the TiOx layer. The holes are considered to be electrostatically attracted to trapped electrons in the TiOx layer after the band excitation. These accumulated charges are the origin of the light-soaking phenomenon. Our results strongly suggest that passivation of the residual OH groups in the TiOx layer is needed to avoid the light-soaking phenomenon by preventing electron trappings, a step that is indispensable in the operation of highly stable IOSCs without UV-light irradiation based o...