Efficient hole transport material formed by atmospheric pressure plasma functionalization of Spiro-OMeTAD
Efficient hole transport material formed by atmospheric pressure plasma functionalization of Spiro-OMeTAD
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DOI：
10.1016/j.mtchem.2020.100321
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发表时间：
2020-09
影响因子：
7.3
通讯作者：
P. Ghosh;A. Ivaturi;D. Bhattacharya;J. Bowen;Tony Nixon;J. Kowal;N. Braithwaite;S. Krishnamurthy
中科院分区：
文献类型：
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作者：
P. Ghosh;A. Ivaturi;D. Bhattacharya;J. Bowen;Tony Nixon;J. Kowal;N. Braithwaite;S. Krishnamurthy
报道了一种使用易于扩展的非热大气压等离子体射流（APPJ）来增加Spiro-OMeCl 2的电导率的技术。对等离子体功能化的研究表明，空穴电导率提高了一个数量级，从原始薄膜的9.4 × 10−7S cm− 1到等离子体处理5分钟后的1.15 × 10−5S cm− 1。等离子体官能化后的电导率值与10- 25% Li-TFSI掺杂的螺-OMeCl报道的电导率值相当。电导率的增加与使用静电力显微镜观察到的相位值的减少。Kelvin探针力显微镜显示等离子体暴露后的功函数增加对应于掺杂的p型性质。X射线光电子能谱显示等离子体功能化膜的表面氧化，以及氮化学的变化，形成更高的结合能的季氮尾。使用紫外-可见光谱法，通过出现500 nm吸收峰也证实了螺环-OMeCl 4的氧化。由于等离子体射流中的高能物质导致的螺环-OMeCl中电荷密度的增加与分子的π-π堆叠的改善的协同贡献被认为是电导率增强的基础。正电荷的增强也可以归因于醌型结构的形成，其中季氮+N=C由于在等离子体表面相互作用期间甲基的损失而形成。这项工作开辟了使用大气压等离子体射流作为一种简单有效的技术来掺杂和功能化Spiro-OMeTAD薄膜的可能性，以规避与化学掺杂剂相关的有害问题。
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 × 10−7S cm−1for the pristine film to 1.15 × 10−5S cm−1for 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 thep-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.