Pérez Gabriel E, Bernardo Gabriel, Gaspar Hugo, Cooper Joshaniel F K, Bastianini Francesco, Parnell Andrew J, Dunbar Alan D F
Department of Chemical and Biological Engineering , The University of Sheffield , Sheffield S1 3JD , U.K.
Department of Physics and Astronomy , The University of Sheffield , Sheffield S3 7RH , U.K.
ACS Appl Mater Interfaces. 2019 Apr 10;11(14):13803-13811. doi: 10.1021/acsami.9b02700. Epub 2019 Mar 26.
Doping poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) is known to improve its conductivity; however, little is known about the thin-film structure of PEDOT:PSS when doped with an asymmetrically charged dopant. In this study, PEDOT:PSS was doped with different concentrations of the zwitterion 3-( N, N dimethylmyristylammonio)propanesulfonate (DYMAP), and its effect on the bulk structure of the films was characterized by neutron reflectivity. The results show that at a low doping concentration, the film separates into a quasi-bilayer structure with lower roughness (10%), increased thickness (18%), and lower electrical conductivity compared to the undoped sample. However, when the doping concentration increases, the film forms into a homogeneous layer and experiences an enhanced conductivity by more than an order of magnitude, a 20% smoother surface, and a 60% thickness increase relative to the pristine sample. Atomic force microscopy (AFM) and profilometry measurements confirmed these findings, and the AFM height and phase images showed the gradually increasing presence of DYMAP on the film surface as a function of the concentration. Neutron reflectivity also showed that the quasi-bilayer structure of the lowest concentration-doped PEDOT:PSS is separated by a graded rather than a well-defined interface. Our findings provide an understanding of the layer structure modification for doped PEDOT:PSS films which should prove important for device applications.
掺杂聚（3,4 - 亚乙基二氧噻吩）：聚（苯乙烯磺酸盐）（PEDOT:PSS）可提高其导电性；然而，对于用不对称带电掺杂剂掺杂时PEDOT:PSS的薄膜结构却知之甚少。在本研究中，PEDOT:PSS用不同浓度的两性离子3 -（N，N - 二甲基肉豆蔻基铵）丙烷磺酸盐（DYMAP）进行掺杂，并通过中子反射率表征其对薄膜整体结构的影响。结果表明，在低掺杂浓度下，薄膜分离成准双层结构，与未掺杂样品相比，粗糙度降低（10%），厚度增加（18%），电导率降低。然而，当掺杂浓度增加时，薄膜形成均匀层，电导率提高超过一个数量级，表面光滑度提高20%，相对于原始样品厚度增加60%。原子力显微镜（AFM）和轮廓测量证实了这些发现，AFM高度和相位图像显示随着浓度的增加，DYMAP在薄膜表面的存在逐渐增加。中子反射率还表明，最低浓度掺杂的PEDOT:PSS的准双层结构由渐变而非明确界定的界面分隔。我们的研究结果有助于理解掺杂PEDOT:PSS薄膜的层结构改性，这对于器件应用应该很重要。
