Tunable Band-Edge Potentials and Charge Storage in Colloidal Tin-Doped Indium Oxide (ITO) Nanocrystals
Tunable Band-Edge Potentials and Charge Storage in Colloidal Tin-Doped Indium Oxide (ITO) Nanocrystals
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DOI：
10.1021/acsnano.1c04660
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发表时间：
2021-08-13
期刊：
影响因子：
17.1
通讯作者：
Gamelin, Daniel R.
中科院分区：
文献类型：
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作者：
Araujo, Jose J.;Brozek, Carl K.;Gamelin, Daniel R.
简并掺杂的金属氧化物纳米晶体（NCs）显示出局域表面等离子体共振（LSPRs），其可通过可调节的过剩载流子密度进行调节。过剩载流子的调制也已被用于控制胶体掺杂金属氧化物纳米晶体中的磁性。过剩的离域导带（CB）电子的增加可通过异价掺杂或通过合成后技术（如电化学或光掺杂）来实现。在此，我们通过实验和建模研究了电荷补偿异价掺杂剂对独立胶体简并掺杂氧化物纳米晶体中过剩导带电子电势的影响。以Sn⁴⁺:In₂O₃（ITO）纳米晶体作为模型体系，我们使用光谱电化学技术来研究异价掺杂和光掺杂之间的差异。我们证明，光掺杂通过相对于导带边提高费米能级来引入过剩导带电子，而异价杂质取代通过相对于外部定义的费米能级稳定导带边来引入过剩导带电子。因此，在光谱上相似的由异价掺杂剂补偿的离域导带电子和在光掺杂过程中由表面阳离子（例如质子）补偿的离域导带电子之间，在电化学上观察到显著差异。理论建模说明了通过异价取代进行电荷补偿和表面电荷补偿所产生的非常不同的电势。光谱电化学滴定能够量化ITO纳米晶体的带边稳定随Sn⁴⁺掺杂的变化。在In₂O₃和ITO纳米晶体中都观察到极大的电容，这使得这些纳米晶体对于可逆电荷存储应用具有吸引力。
Degenerately doped metal-oxide nanocrystals (NCs) show localized surface plasmon resonances (LSPRs) that are tunable via their tunable excess charge-carrier densities. Modulation of excess charge carriers has also been used to control magnetism in colloidal doped metal- oxide NCs. The addition of excess delocalized conduction-band (CB) electrons can be achieved through aliovalent doping or by postsynthetic techniques such as electrochemistry or photodoping. Here, we examine the influence of charge-compensating aliovalent dopants on the potentials of excess CB electrons in freestanding colloidal degenerately doped oxide NCs, both experimentally and through modeling. Taking Sn4+:In2O3 (ITO) NCs as a model system, we use spectroelectrochemical techniques to examine differences between aliovalent doping and photodoping. We demonstrate that whereas photodoping introduces excess CB electrons by raising the Fermi level relative to the CB edge, aliovalent impurity substitution introduces excess CB electrons by stabilizing the CB edge relative to an externally defined Fermi level. Significant differences are thus observed electrochemically between spectroscopically similar delocalized CB electrons compensated by aliovalent dopants and those compensated by surface cations (e.g., protons) during photodoping. Theoretical modeling illustrates the very different potentials that arise from charge compensation via aliovalent substitution and surface charge compensation. Spectroelectrochemical titrations allow the ITO NC band-edge stabilization as a function of Sn4+ doping to be quantified. Extremely large capacitances are observed in both In2O3 and ITO NCs, making these NCs attractive for reversible charge-storage applications.