Evolution of the Stoichiometry and Electronic Structure of Cobalt Oxide in Thermally Treated Co-Doped ZnO Nanorods for Solar Cells
Evolution of the Stoichiometry and Electronic Structure of Cobalt Oxide in Thermally Treated Co-Doped ZnO Nanorods for Solar Cells
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DOI：
10.1021/acsanm.9b00574
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发表时间：
2019-07-01
影响因子：
5.9
通讯作者：
McIlroy, David
中科院分区：
文献类型：
--
作者：
Echeverria, Elena;Kaphle, Amrit;McIlroy, David
用光电子能谱(XPS、UPS)和X射线衍射仪(X射线衍射仪)研究了退火对化学浴沉积法制备的Co掺杂纳米棒的化学计量比和电子结构的影响。生长的掺钴氧化锌纳米晶的Co2p芯能级状态与Co3O4化学计量比一致，与Co浓度无关。生长的材料在865K以上退火后，形成Co2p芯级卫星态，这与CoO的形成相一致。态的价带密度也随退火而变化，在费米能级和其下1 eV之间形成新的态密度。新的价带态也与CoO的形成相一致。氧化钴化学计量比从Co3O4到CoO的这种变化导致了由于O配位减少而产生的锌-，这与俄歇分析一致。此外，暴露在空气中，Co3O4向CoO的演化是不可逆的。钴的氧化状态是太阳能电池材料性能的关键参数。
The effects of annealing on the stoichiometry and electronic structure of Co-doped ZnO nanorods (NRs), as prepared by chemical bath deposition (CBD), were investigated by photoemission spectroscopies (XPS and UPS) and X-ray diffraction (XRD). The Co 2p core level state of the as-grown Co-doped ZnO NRs is consistent with a Co3O4 stoichiometry, independent of the Co concentration. Upon annealing of the as-grown material above 865 K, a Co 2p core level satellite state forms, which is consistent with the formation of CoO. The valence band density of states also exhibits changes with annealing, where a new density of states forms between the Fermi level and 1 eV below. The new valence band states are also consistent with the formation of CoO. This change in the cobalt oxide stoichiometry from Co3O4 to CoO results in Zn- due to reduced O coordination, consistent with the Auger analysis. In addition, the evolution of Co3O4 to CoO is irreversible upon exposure to air. The oxidation state of Co is a key parameter in the material's performance when used for solar cells.