Complete Demonstration of the Valence Electronic Structure Inside a Practical Organic Solar Cell Probed by Low Energy Photoemission
Complete Demonstration of the Valence Electronic Structure Inside a Practical Organic Solar Cell Probed by Low Energy Photoemission
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DOI：
10.1002/aenm.201301354
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发表时间：
2014-05-01
影响因子：
27.8
通讯作者：
Ishii, Hisao
中科院分区：
文献类型：
--
作者：
Nakayama, Yasuo;Thanh Luan Nguyen;Ishii, Hisao
利用低能紫外光电子能谱（LE-UPS）和光电子产额谱（PYS）研究了由铜酞菁（CuPc）、富勒烯（C-60）和浴铜灵（BCP）组成的三层结构的有机光伏（OPV）器件内部的完整电子结构.基于LE-UPS结果，说明了整个器件的分子轨道能量排列和静电势分布。一个有利的电位梯度进行光生空穴和电子被证明是建立自发的CuPc和BCP层，分别。此外，LE-UPS的灵敏度测量清楚地揭示了有机薄膜中能隙区的微弱态密度分布。通过这些间隙状态的存在实现了与两个电极的基本上无势垒的接触。在模拟太阳光照射下的电子结构进行了检查，以阐明在开路条件下的工作器件内部的电子结构的目的。这些结果在实验上表明每种有机材料，特别是BCP缓冲层的电子功能性对电池效率的影响。
The complete electronic structure inside a practical organic photovoltaic (OPV) device consisting of a trilayer structure of copper-phthalocyanine (CuPc), fullerene (C-60), and bathocuproine (BCP) is demonstrated using low-energy ultraviolet photoelectron spectroscopy (LE-UPS) and photoelectron yield spectroscopy (PYS). The molecular orbital energy alignment and electrostatic potential distribution throughout the entire device is illustrated based on the LE-UPS results. A favorable potential gradient to carry the photogenerated holes and electrons is manifested to be built spontaneously in the CuPc and BCP layers, respectively. Furthermore, the ultrahigh sensitivity measurements of LE-UPS clearly unveil the distributions of faint density-of-states in the energy-gap region in the organic films. Substantially barrierless contacts to both electrodes are fulfilled by the existence of these gap states. The electronic structure under simulated sunlight illumination is examined for the purpose of elucidating the electronic structures inside the working devices in the open-circuit condition. These results indicate experimentally the electronic functionalities of each organic material, in particular of the BCP buffer layer, on the cell efficiency.