Lee Junghyun, Chhatre Shrirang, Sitarik Peter, Wu Yuhang, Baugh Quintin, Martin David C
Department of Materials Science and Engineering, University of Delaware, Newark, Delaware 19716, United States.
Department of Biomedical Engineering, University of Delaware, Newark, Delaware 19716, United States.
ACS Appl Mater Interfaces. 2022 Sep 21;14(37):42289-42297. doi: 10.1021/acsami.2c10149. Epub 2022 Sep 12.
Organic electrochemical transistors (OECTs) are promising bioelectronic devices, especially because of their ability to transport charge both ionically and electronically. Conductive polymers are typically used as the active materials of OECTs. Crosslinked, cast, and dried films of commercially available poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) suspensions are commonly and widely used for OECTs so far. Electrochemical polymerization of PEDOT from 3,4-ethylenedioxythiophene (EDOT) monomer can also be used to fabricate OECTs; however, this approach has not been investigated in as much detail. In particular, the role of various counterions that can be incorporated into the PEDOT films of OECTs has not been systematically studied. Here, we report the electrochemical fabrication and characterization of OECTs using PEDOT with several different counterion salts including lithium perchlorate (LiClO), sodium -toluene sulfonate (TS), and poly(sodium 4-styrene sulfonate) (PSS). We found that the characteristic dimensions of PEDOT films deposited on the electrodes could be precisely controlled by total charge density, with a nominal thickness of about one micron requiring a current density of about 0.6 C/cm regardless of the choice of counterion. The films with the PSS counterion were relatively smooth, while PEDOT films prepared with the TS and LiClO were much rougher due to the sizes of counterions. The PEDOT films with TS and PSS grew along the substrate surface (in-plane direction) much faster than with LiClO. The maximum transconductance () of a PEDOT OECT was 46 mS with TS as the counterion with the high on-current level (>10 mA) based on the large channel area. These results provide an effective and efficient way to fabricate OECTs with various monomers and additives as active materials in order to modify the device characteristics for further applications.
有机电化学晶体管（OECTs）是很有前景的生物电子器件，特别是因为它们具有离子和电子双电荷传输能力。导电聚合物通常用作OECTs的活性材料。迄今为止，市售聚（3,4 - 乙撑二氧噻吩）：聚（苯乙烯磺酸盐）（PEDOT:PSS）悬浮液的交联、浇铸和干燥膜被普遍且广泛地用于OECTs。由3,4 - 乙撑二氧噻吩（EDOT）单体进行PEDOT的电化学聚合也可用于制造OECTs；然而，这种方法尚未得到详细研究。特别是，可掺入OECTs的PEDOT膜中的各种抗衡离子的作用尚未得到系统研究。在此，我们报告了使用PEDOT与几种不同的抗衡离子盐（包括高氯酸锂（LiClO）、对甲苯磺酸钠（TS）和聚（4 - 苯乙烯磺酸钠）（PSS））进行OECTs的电化学制备和表征。我们发现，沉积在电极上的PEDOT膜的特征尺寸可以通过总电荷密度精确控制，无论抗衡离子的选择如何，名义厚度约为一微米需要约0.6 C/cm的电流密度。具有PSS抗衡离子的膜相对光滑，而用TS和LiClO制备的PEDOT膜由于抗衡离子的尺寸而粗糙得多。具有TS和PSS的PEDOT膜沿基板表面（面内方向）生长的速度比LiClO快得多。以TS作为抗衡离子时，基于大沟道面积，PEDOT OECT的最大跨导（）为46 mS，导通电流水平较高（>10 mA）。这些结果提供了一种有效且高效的方法，以各种单体和添加剂作为活性材料来制造OECTs，从而为进一步应用修改器件特性。
