Abstract A technique to increase the conductivity of Spiro-OMeTAD using an easily scalable, non-thermal atmospheric pressure plasma jet (APPJ) is reported. An investigation of plasma functionalization demonstrated an enhancement in hole conductivity by over an order of magnitude from 9.4 × 10−7 S cm−1 for the pristine film to 1.15 × 10−5 S cm−1 for films after 5 minutes of plasma treatment. The conductivity value after plasma functionalization was comparable to that reported for 10–25% Li-TFSI-doped Spiro-OMeTAD. The increase in conductivity was correlated with a reduction in phase value observed using electrostatic force microscopy. Kelvin probe force microscopy showed an increase in work function after plasma exposure corresponding to the p-type nature of the doping. X-ray photoelectron spectroscopy revealed surface oxidation of plasma-functionalized films, as well as variation in nitrogen chemistry, with the formation of a higher binding energy quaternary nitrogen tail. Oxidation of Spiro-OMeTAD was also confirmed by the appearance of the 500 nm absorption peak using UV–vis spectroscopy. The synergistic contribution of increase in charge density in Spiro-OMeTAD due to the energetic species in the plasma jet coupled with improvement in π-π stacking of the molecules is thought to underlie the conductivity enhancement. The enhancement in positive charges can also be attributed to the formation of quinoid structures with quaternary nitrogen +N=C formed due to loss of methyl groups during plasma surface interaction. This work opens up the possibility of using an atmospheric pressure plasma jet as a simple and effective technique for doping and functionalizing Spiro-OMeTAD thin films to circumvent the detrimental issues associated with chemical dopants.

中文翻译：

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Spiro-OMeTAD常压等离子体功能化形成的高效空穴传输材料

摘要报道了一种使用易于扩展的非热常压等离子体射流 (APPJ) 来提高 Spiro-OMeTAD 电导率的技术。对等离子体功能化的研究表明，经过 5 分钟的等离子体处理后，空穴电导率提高了一个数量级，从原始薄膜的 9.4 × 10-7 S cm-1 到薄膜的 1.15 × 10-5 S cm-1。等离子体功能化后的电导率值与 10-25% Li-TFSI 掺杂的 Spiro-OMeTAD 报告的电导率值相当。电导率的增加与使用静电力显微镜观察到的相值的减少相关。开尔文探针力显微镜显示等离子体暴露后功函数增加，对应于掺杂的 p 型性质。X 射线光电子能谱揭示了等离子体功能化薄膜的表面氧化，以及氮化学的变化，形成了更高结合能的季氮尾。Spiro-OMeTAD 的氧化也通过使用紫外-可见光谱的 500 nm 吸收峰的出现得到证实。由于等离子体射流中的高能物质以及分子 π-π 堆积的改善，Spiro-OMeTAD 中电荷密度增加的协同贡献被认为是电导率增强的基础。正电荷的增强也可归因于在等离子体表面相互作用期间由于甲基基团的损失而形成具有季氮+N=C的醌型结构的形成。