Bithiopheneimide-Dithienosilole/Dithienogermole Copolymers for Efficient Solar Cells: Information from Structure-Property-Device Performance Correlations and Comparison to Thieno[3,4-c]pyrrole-4,6-dione Analogues
Bithiopheneimide-Dithienosilole/Dithienogermole Copolymers for Efficient Solar Cells: Information from Structure-Property-Device Performance Correlations and Comparison to Thieno[3,4-c]pyrrole-4,6-dione Analogues
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DOI：
10.1021/ja3081583
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发表时间：
2012-11-07
影响因子：
15
通讯作者：
Marks, Tobin J.
中科院分区：
文献类型：
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作者：
Guo, Xugang;Zhou, Nanjia;Marks, Tobin J.
聚合物太阳能电池(PSC)的发展离不开从新颖的积木中合理地创造聚合物半导体。我们报道了一系列用于体异质结(BHJ)PSCs的新型联噻吩亚胺给受体共聚物。联噻吩亚胺的电子缺陷压缩了聚合物的带隙，降低了同系物，这是最大化功率转换效率(PCE)所必需的。虽然二硫吩桥联R2Si-&Gt；R2Ge对带隙的影响很小，但它极大地改变了HOMO能量。此外，酰亚胺N-取代基的变化对聚合物的光电性能影响不大，但对溶解度和微观结构有很大影响。掠入射广角X射线散射(GIWAXS)表明，支化的N-烷基取代基比直链N-烷基取代基增加了聚合物的pi-pi间距，并且基于二硫硅烷的PBTISi系列比基于二硫代锗摩尔的PBTIGe类似物表现出更有序的堆积。通过硫代[3，4-c]吡咯-4，6-二酮(TPD)-二硫代硅烷共聚物PTPDSi，进一步揭示了结构-性质-器件性能之间的关系。密度泛函理论计算和光谱分析表明，与TPD类似物相比，TPD基聚合物通过分子内(噻吩基)S中心点O(羰基)相互作用实现了更大的亚单位-亚基共面性，GIWAXS表明PBTISi-C8具有更低的片层有序性，但pi-pi间距更小。以联噻吩亚胺聚合物为施主、PC71BM为受主的倒装BHJ太阳电池具有良好的器件性能，PCEs高达6.41%，V-oc&Gt；0.80V。在类似电池中，TPD类似物表现出0.08V的高V-oc，PCE提高6.83%，这主要是由于较高的酰亚胺基团密度引起了较低的HOMO。这些结果证明了基于BTI的聚合物在高性能太阳能电池中的潜力，并为TPD、BTI和相关聚合物半导体的结构-性能关系提供了概括性的见解。
Rational creation of polymeric semiconductors from novel building blocks is critical to polymer solar cell (PSC) development. We report a new series of bithiopheneimide-based donor-acceptor copolymers for bulk-heterojunction (BHJ) PSCs. The bithiopheneimide electron deficiency compresses polymer bandgaps and lowers the HOMOs-essential to maximize power conversion efficiency (PCE). While the dithiophene bridge progression R2Si -> R2Ge minimally impacts bandgaps, it substantially alters the HOMO energies. Furthermore, imide N-substituent variation has negligible impact on polymer opto-electrical properties, but greatly affects solubility and microstructure. Grazing incidence wide-angle X-ray scattering (GIWAXS) indicates that branched N-alkyl substituents increased polymer pi-pi spacings vs linear N-alkyl substituents, and the dithienosilole-based PBTISi series exhibits more ordered packing than the dithienogermole-based PBTIGe analogues. Further insights into structure-property-device performance correlations are provided by a thieno[3,4-c]pyrrole-4,6-dione (TPD)-dithienosilole copolymer PTPDSi. DFT computation and optical spectroscopy show that the TPD-based polymers achieve greater subunit-subunit coplanarity via intramolecular (thienyl)S center dot center dot center dot O(carbonyl) interactions, and GIWAXS indicates that PBTISi-C8 has lower lamellar Ordering, but closer pi-pi Spacing than does the TPD-based analogue. Inverted BHJ solar cells using bithiopheneimide-based polymer as donor and PC71BM as acceptor exhibit promising device performance with PCEs up to 6.41% and V-oc > 0.80 V. In analogous cells, the TPD analogue exhibits 0.08 V higher V-oc with an enhanced PCE of 6.83%, mainly attributable to the lower-lying HOMO induced by the higher imide group density. These results demonstrate the potential of BTI-based polymers for high-performance solar cells, and provide generalizable insights into structure-property relationships in TPD, BTI, and related polymer semiconductors.