Koh Qi-Mian, Tang Cindy Guanyu, Ang Mervin Chun-Yi, Choo Kim-Kian, Seah Qiu-Jing, Png Rui-Qi, Chua Lay-Lay, Ho Peter K H
Department of Chemistry, National University of Singapore, Singapore, Singapore.
Department of Physics, National University of Singapore, Singapore, Singapore.
Nat Commun. 2021 Jun 7;12(1):3345. doi: 10.1038/s41467-021-23347-x.
It is widely thought that the water-oxidation reaction limits the maximum work function to about 5.25 eV for hole-doped semiconductors exposed to the ambient, constrained by the oxidation potential of air-saturated water. Here, we show that polymer organic semiconductors, when hole-doped, can show work functions up to 5.9 eV, and yet remain stable in the ambient. We further show that de-doping of the polymer is not determined by the oxidation of bulk water, as previously thought, due to its general absence, but by the counter-balancing anion and its ubiquitously hydrated complexes. The effective donor levels of these species, representing the edge of the 'chemical' density of states, can be depressed to about 6.0 eV below vacuum level. This can be achieved by raising the oxidation potential for hydronium generation, using large super-acid anions that are themselves also stable against oxidation. In this way, we demonstrate that poly(fluorene-alt-triarylamine) derivatives with tethered perfluoroalkyl-sulfonylimidosulfonyl anions can provide ambient solution-processability directly in the ultrahigh-workfunction hole-doped state to give films with good thermal stability. These results lay the path for design of soft materials for battery, bio-electronic and thermoelectric applications.
人们普遍认为，对于暴露在环境中的空穴掺杂半导体，水氧化反应将其最大功函数限制在约5.25电子伏特，这受到空气饱和水的氧化电位的限制。在此，我们表明，聚合物有机半导体在空穴掺杂时，功函数可高达5.9电子伏特，且在环境中仍保持稳定。我们进一步表明，聚合物的去掺杂并非如先前所想的那样由大量水的氧化决定，因为大量水通常不存在，而是由平衡阴离子及其普遍存在的水合络合物决定。这些物种的有效施主能级，代表“化学”态密度的边缘，可被压低至真空能级以下约6.0电子伏特。这可以通过使用本身也抗氧化稳定的大的超酸阴离子提高水合氢离子生成的氧化电位来实现。通过这种方式，我们证明了带有连接的全氟烷基磺酰亚胺磺酰阴离子的聚（芴-alt-三芳基胺）衍生物可以直接在超高功函数空穴掺杂状态下提供环境溶液可加工性，从而得到具有良好热稳定性的薄膜。这些结果为用于电池、生物电子和热电应用的软材料的设计铺平了道路。
