Tamura Yuto, Suzuki Mitsuharu, Nakagawa Takaki, Koganezawa Tomoyuki, Masuo Sadahiro, Hayashi Hironobu, Aratani Naoki, Yamada Hiroko
Division of Materials Science, Graduate School of Science and Technology, Nara Institute of Science and Technology 8916-5 Takayama-cho Ikoma Nara 630-0192 Japan
Department of Applied Chemistry and Environment, Kwansei Gakuin University 2-1 Gakuen Sanda Hyogo 669-1337 Japan.
RSC Adv. 2018 Oct 15;8(61):35237-35245. doi: 10.1039/c8ra07398h. eCollection 2018 Oct 10.
The additive effect on small-molecule-based p-i-n-type devices has been little investigated so far. We focus on the improvement of the miscibility of tetrabenzoporphyrin (BP) and [6,6]-phenyl-C-butyric acid methyl ester (PCBM) blend film by addition of fullerene-linked tetrabenzoporphyrin (BP-C) as an additive to the interlayer (i-layer). BP is one of the most promising p-type organic semiconductors, and BP films can be prepared readily by heating as-cast films of the precursor (a bicyclo[2.2.2]octadiene-fused porphyrin; CP), that results in changes from amorphous CP films to polycrystalline BP films. Because of the high crystallinity of BP, large BP grains on the scale of tens to hundreds of nanometers are generated in blend films of BP and PCBM during film fabrication. We found that the addition of BP-C as an additive (3, 5, 7, and 10 wt%) to the i-layer composed of BP and PCBM improves the miscibility of BP and PCBM. The power conversion efficiency of p-i-n-type organic solar cells consisting of a blend film of BP and PCBM (i-layer) sandwiched by BP (p-layer) and PCBM (n-layer) improved by up to 50% as compared to that of a control device after the addition of BP-C to the i-layer. The film morphology was investigated using atomic force microscopy, fluorescence microspectroscopy, two-dimensional grazing-incident wide-angle X-ray diffraction measurements, and scanning electron microscopy. Interacting with both BP and PCBM, the addition of BP-C led to changes in the grain size as well as an increase in the size of the BP/PCBM interface and hence effective charge separation in the p-i-n device. This morphological improvement is attributable to the ability of BP-C, which exhibits the characteristics of both BP and C, to promote the compatibility of BP and PCBM. This study is a significant step towards the development of high-performance p-i-n-type solar cells and should pave the way for the fabrication of high-performance bulk-heterojunction layers in solution-processed organic photovoltaic devices.
到目前为止，基于小分子的p-i-n型器件的添加剂效应鲜少得到研究。我们致力于通过向中间层（i层）添加富勒烯连接的四苯并卟啉（BP-C）作为添加剂，来改善四苯并卟啉（BP）和[6,6]-苯基-C-丁酸甲酯（PCBM）共混膜的混溶性。BP是最有前景的p型有机半导体之一，通过加热前驱体（双环[2.2.2]辛二烯稠合卟啉；CP）的铸膜可轻松制备BP膜，这会导致非晶态CP膜转变为多晶BP膜。由于BP具有高结晶性，在薄膜制备过程中，BP和PCBM的共混膜中会生成尺度为数十到数百纳米的大BP晶粒。我们发现，向由BP和PCBM组成的i层中添加BP-C作为添加剂（3、5、7和10重量%）可改善BP和PCBM的混溶性。与对照器件相比，在i层中添加BP-C后，由BP（p层）和PCBM（n层）夹着的BP和PCBM共混膜（i层）构成的p-i-n型有机太阳能电池的功率转换效率提高了高达50%。使用原子力显微镜、荧光显微光谱、二维掠入射广角X射线衍射测量和扫描电子显微镜对薄膜形态进行了研究。BP-C与BP和PCBM都相互作用，导致晶粒尺寸发生变化，以及BP/PCBM界面尺寸增大，从而在p-i-n器件中实现有效的电荷分离。这种形态学上的改善归因于BP-C兼具BP和C的特性，能够促进BP和PCBM的相容性。这项研究是朝着开发高性能p-i-n型太阳能电池迈出的重要一步，应为在溶液处理的有机光伏器件中制造高性能本体异质结层铺平道路。
