Woon K L, Wong W S, Chanlek N, Nakajima H, Tunmee S, Lee V S, Ariffin A, Songsiriritthigul P
Low Dimensional Material Research Center, Department of Physics, University Malaya 50603 Kuala Lumpur Malaysia
Synchrotron Light Research Institute Nakhon Ratchasima 30000 Thailand.
RSC Adv. 2020 May 6;10(30):17673-17680. doi: 10.1039/d0ra02575e. eCollection 2020 May 5.
Poly(3,4-ethylenedioxythiophene)polystyrene sulfonate (PEDOT:PSS) is often used as a hole injection and extractor for various organic electronic devices. This study investigated whether it is possible to n-dope PEDOT:PSS with barium acetylacetonate (Ba(acac)) to change its work function so that to be more suitable for electron injection and extraction. Molecular dynamics simulations suggested that barium cations can interact with the aromatic rings of PEDOT and the negatively charged sulfonate in PSS. At high doping concentration, we found that PEDOT became dedoped and precipitated resulting in a clear solution after filtration. The absence of the absorption peak of PEDOT at 263 nm indicates the removal of PEDOT after filtration. The shift in O 1s to a lower binding energy as seen in X-ray photoelectron spectroscopy suggested that the polystyrene sulfonic acids are being ionized to form barium polystyrene sulfonate (Ba-PSS). By spin-coating the solution on top of indium tin oxide, the work function can be adjusted to as low as 3.6 eV. The ability of such a mixture to inject and extract electrons is demonstrated using 2,7-bis(diphenylphosphoryl)-9,9'-spirobifluorene as an electron transporting layer. We attributed the lowering of the work function as the result of the formation of an interfacial dipole as large as 1.37 eV at the ITO/Ba-PSS interface.
聚（3,4 - 亚乙基二氧噻吩）聚苯乙烯磺酸盐（PEDOT:PSS）常被用作各种有机电子器件的空穴注入和提取材料。本研究调查了用乙酰丙酮钡（Ba(acac)）对PEDOT:PSS进行n型掺杂以改变其功函数从而使其更适合电子注入和提取是否可行。分子动力学模拟表明钡阳离子可与PEDOT的芳环以及PSS中带负电荷的磺酸盐相互作用。在高掺杂浓度下，我们发现PEDOT去掺杂并沉淀，过滤后得到澄清溶液。在263 nm处PEDOT吸收峰的消失表明过滤后PEDOT已被去除。X射线光电子能谱中O 1s向较低结合能的位移表明聚苯乙烯磺酸正在被电离以形成聚苯乙烯磺酸钡（Ba - PSS）。通过将该溶液旋涂在氧化铟锡顶部，功函数可被调节至低至3.6 eV。使用2,7 - 双（二苯基磷酰基）- 9,9'-螺二芴作为电子传输层证明了这种混合物注入和提取电子的能力。我们将功函数的降低归因于在ITO/Ba - PSS界面形成了高达1.37 eV的界面偶极。
