Solar Cell Efficiency, Self-Assembly, and Dipole-Dipole Interactions of Isomorphic Narrow-Band-Gap Molecules
Solar Cell Efficiency, Self-Assembly, and Dipole-Dipole Interactions of Isomorphic Narrow-Band-Gap Molecules
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DOI：
10.1021/ja3050713
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发表时间：
2012-10-10
影响因子：
15
通讯作者：
Heeger, Alan J.
中科院分区：
文献类型：
--
作者：
Takacs, Christopher J.;Sun, Yanming;Heeger, Alan J.
我们研究的偶极矩和构象稳定性的自组装和太阳能电池的性能内的一系列同构，溶液加工分子的相关性。这些电荷转移发色团由D-1-A-D-A-D-1结构描述，其包含富电子的2-己基联噻吩和3，3 ′-二-2-乙基己基亚甲硅烷基-2，2 ′-联噻吩部分分别作为供体单元D-1和D。使用结构单元2，1，3-苯并噻二唑（BT）和[1，2，5]噻二唑并[3，4-c]吡啶（PT）作为缺电子受体单元A。使用紫外可见光谱、场效应晶体管、太阳能电池器件、掠入射广角X射线散射和透射电子显微镜的组合，研究了具有不同区域化学和对称性的三种含PT化合物（1-3）以及基于BT的化合物5，5 '-bis{（4-（7-己基噻吩-2-基）噻吩-2-基）-[1，2，5]噻二唑苯}-3，3 ′-二-2-乙基己基亚甲硅烷基-2，2 ′-联噻吩（4）在溶液中、在薄膜中以及作为与电子受体的共混物进行比较和对比[6，6]-苯基-C-70-丁酸甲酯。PT受体，1和2的对称取向的分子，产生高度有序的共混薄膜。用溶剂添加剂1，8-二碘辛烷处理的最佳膜显示出供体“微晶”长度尺度在15-35 nm的量级上，光伏功率转换效率（PCE）分别为7.0和5.6%。具有PT杂环的不对称取向的化合物3在结晶行为方面显示出细微的差异，并且最佳PCE为3.2%。相比之下，含BT的供体4的共混物是高度无序的，并且产生低于0.2%的PCE。我们推测，在自组装的差异产生的强烈影响的BT受体和它的取向上的净偶极矩和几何描述的发色团。
We examine the correlations of the dipole moment and conformational stability to the self-assembly and solar cell performance within a series of isomorphic, solution-processable molecules. These charge-transfer chromophores are described by a D-1-A-D-A-D-1 structure comprising electron-rich 2-hexylbithiophene and 3,3'-di-2-ethylhexylsilylene-2,2'-bithiophene moieties as the donor units D-1 and D, respectively. The building blocks 2,1,3-benzothiadiazole (BT) and [1,2,5]thiadiazolo[3,4-c]pyridine (PT) were used as the electron-deficient acceptor units A. Using a combination of UV-visible spectroscopy, field-effect transistors, solar cell devices, grazing incident wide-angle X-ray scattering, and transmission electron microscopy, three PT-containing compounds (1-3) with varying regiochemistry and symmetry, together with the BT-based compound 5,5'-bis{(4-(7-hexylthiophen-2-yl)thiophen-2-yl)-[1,2,5]thiadiazolobenzene}-3,3'-di-2-ethylhexylsilylene-2,2'-bithiophene (4), are compared and contrasted in solution, in thin films, and as blends with the electron acceptor [6,6]-phenyl-C-70-butyric acid methyl ester. The molecules with symmetric orientations of the PT acceptor, 1 and 2, yield highly ordered blended thin films. The best films, processed with the solvent additive 1,8-diiodooctane, show donor "crystallite" length scales on the order or 15-35 nm and photovoltaic power conversion efficiencies (PCEs) of 7.0 and 5.6%, respectively. Compound 3, with an unsymmetrical orientation of PT heterocycles, shows subtle differences in the crystallization behavior and a best PCE of 3.2%. In contrast, blends of the BT-containing donor 4 are highly disordered and give PCEs below 0.2%. We speculate that the differences in self-assembly arise from the strong influence of the BT acceptor and its orientation on the net dipole moment and geometric description of the chromophore.