Dibenzothiophene-S,S-dioxide-bispyridinium-fluorene-based polyelectrolytes for cathode buffer layers of polymer solar cells
Dibenzothiophene-S,S-dioxide-bispyridinium-fluorene-based polyelectrolytes for cathode buffer layers of polymer solar cells
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DOI：
10.1039/d0py00416b
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发表时间：
2020-06-07
影响因子：
4.6
通讯作者：
Cao, Yong
中科院分区：
文献类型：
--
作者：
Chen, Guiting;Cheng, Dan;Cao, Yong
本文提出了一种新型的缺电子共轭水/醇溶于水/醇的聚电解质，它由二苯并噻吩基-S、S-二氧化物、双吡啶盐和带有环氧乙烷侧链的荧烯组成。以前我们已经合成了另一种WSPE(PFSOPyCl)，其骨架与PFSOPyCl-E相同，但带有辛基侧链。在poly[4，8-bis(2-ethylhexyloxyl)benzo[1，2-b:4，5-b‘]dithiophene-2，6-diyl-alt-ethylhexyl-3-fluorothithieno[3，4-b]thiophene-2-carboxylate-4，6-diyl](PtB7)：[6，6]-苯基-C-71丁酸甲酯(PC71BM)体系的倒置聚合物太阳电池(PSC)中应用了PFSOPyCl2和PFSOPyClE作为阴极缓冲材料(CBM)，同时提高了开路电压(V-oc)，当插入这些阴极缓冲层(CBL)时，可以获得短路电流密度(J(Sc))和填充因子(Ff)。研究发现，这些CBL可以在氧化铟锡(ITO)/有源层界面上建立定向偶极子，导致ITO功函数(WF)的减小和V-oc的改善。PSCs的J(Sc)和Ff通过多种机制增加。首先，这些CBL的还原ITO WF(4.30-4.32 eV)、深LUMO能级(E-LUMO)(4.04-4.10 eV)和PC71BM的E-LUMO(类似于3.90 eV)之间的能级排列可以产生良好的欧姆接触，有利于电子的提取和传输。其次，这些CBL能够在界面上掺杂PC71BM，在器件中诱导有效的电子传输路径。此外，这些极性聚合物CBL还可以改善ITO与有源层之间的相容性，从而降低界面电阻。值得注意的是，PFSOPyCl-E的阴极修饰性能优于PFSOPyCl，这可能是由于含有高极性和柔韧性的环氧乙烷侧链的PFSOPyCl-E与ITO的润湿性更好，薄膜比PFSOPyCl更光滑。因此，经PFSOPyCl-E改性的器件具有较低的接触电阻、较高的Ff和J(Sc)。因此，这类缺电子共轭WSPE是很有前途的高性能PSCs的CBM。
Herein, a novel electron-deficient conjugated water/alcohol-soluble polyelectrolyte (WSPE) named PFSOPyCl-E, consisting of dibenzothiophene-S,S-dioxide, bispyridinium salts and fluorene with ethylene oxide side chains, was presented. Previously we have synthesized another WSPE (PFSOPyCl) composed of the same backbone as that of PFSOPyCl-E but with octyl side chains. PFSOPyCl and PFSOPyCl-E were applied as cathode buffer materials (CBMs) to inverted polymer solar cells (PSCs) of poly[4,8-bis(2-ethylhexyloxyl)benzo[1,2-b:4,5-b ']dithiophene-2,6-diyl-alt-ethylhexyl-3-fluorothithieno[3,4-b]thiophene-2-carboxylate-4,6-diyl] (PTB7):[6,6]-phenyl-C-71 butyric acid methyl ester (PC71BM) systems, and simultaneous enhancements in open-circuit voltage (V-oc), short-circuit current density (J(sc)) and fill factor (FF) could be achieved when inserting these cathode buffer layers (CBLs). It was found that these CBLs could build directed dipoles at the indium tin oxide (ITO)/active layer interfaces, leading to the reductions in the ITO work function (WF) and improvements in V-oc for the modified devices. The J(sc) and FFs of PSCs were increased by several mechanisms. Firstly, the energy level alignments between the reduced ITO WFs (4.30-4.32 eV), deep LUMO energy levels (E-LUMO) of these CBLs (4.04-4.10 eV) and E-LUMO of PC71BM (similar to 3.90 eV) could generate good ohmic contacts, facilitating electron extractions and transportations. Secondly, these CBLs were able to n-dope PC71BM at the interfaces, inducing efficient electron-transporting pathways in the devices. Moreover, these polar polymeric CBLs could improve the compatibilities between ITO and the active layers, thus decreasing the interfacial resistances. It is worth noting that PFSOPyCl-E showed better cathode-modifying performance than PFSOPyCl, probably since PFSOPyCl-E with ethylene oxide side chains of high polarity and flexibility possessed better wettability with ITO and smoother films than PFSOPyCl. Hence, the devices modified by PFSOPyCl-E displayed lower contact resistances and higher FFs and J(sc) than the PFSOPyCl-modified ones. Therefore, this class of electron-deficient conjugated WSPEs are promising CBMs for high-performance PSCs.