Combinatorial Discovery of Lanthanum–Tantalum Oxynitride Solar Light Absorbers with Dilute Nitrogen for Solar Fuel Applications,ACS Combinatorial Science

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Combinatorial Discovery of Lanthanum–Tantalum Oxynitride Solar Light Absorbers with Dilute Nitrogen for Solar Fuel Applications
ACS Combinatorial Science Pub Date : 2017-12-11 00:00:00 , DOI: 10.1021/acscombsci.7b00143
Santosh K. Suram ₁ , Sean W. Fackler ₂ , Lan Zhou ₁ , Alpha T. N’Diaye ₃ , Walter S. Drisdell ₂ , Junko Yano _{2,

4} , John M. Gregoire ₁

Affiliation

Oxynitrides with the photoelectrochemical stability of oxides and desirable band energetics of nitrides comprise a promising class of materials for solar photochemistry. Challenges in synthesizing a wide variety of oxynitride materials has limited exploration of this class of functional materials, which we address using a reactive cosputtering combined with rapid thermal processing method to synthesize multi-cation–multi-anion libraries. We demonstrate the synthesis of a La_xTa_1–xO_yN_z thin film composition spread library and its characterization by both traditional thin film materials characterization and custom combinatorial optical spectroscopy and X-ray absorption near edge spectroscopy (XANES) techniques, ultimately establishing structure-chemistry-property relationships. We observe that over a substantial La–Ta composition range the thin films crystallize in the same perovskite LaTaON₂ structure with significant variation of anion chemistry. The relative invariance in optical band gap demonstrates a remarkable decoupling of composition and band energetics so that the composition can be optimized while retaining the desirable 2 eV band gap energy. We also demonstrate the intercalation of diatomic nitrogen into the La₃TaO₇ structure, which gives rise to a direct-allowed optical transition at 2.2 eV, less than half the value of the oxide’s band gap. These findings motivate further exploration of the visible light response of this material that is predicted to be stable over a wide range of electrochemical potential.

中文翻译：

太阳能电池应用中的稀氮氮化镧-氧氮化钽太阳光吸收剂的组合发现

具有氧化物的光电化学稳定性和所需的氮化物带能的氧氮化物包括用于太阳能光化学的有前途的一类材料。合成多种氧氮化物材料所面临的挑战限制了这类功能材料的探索，我们使用反应性共溅射结合快速热处理方法来合成多阳离子-多阴离子文库来解决这些问题。我们展示了La _x Ta _{1– x} O _y N _z的合成通过传统的薄膜材料表征和定制的组合光学光谱学以及X射线吸收近边缘光谱（XANES）技术，对薄膜成分传播库及其表征进行了鉴定，最终建立了结构-化学-性质的关系。我们观察到，在相当大的La-Ta组成范围内，薄膜以相同的钙钛矿型LaTaON ₂结构结晶，但阴离子化学变化很大。光学带隙的相对不变性表明，成分与能带能量之间存在显着的去耦关系，因此可以在保持所需2 eV带隙能量的同时优化成分。我们还演示了将双原子氮嵌入La ₃ TaO _7中结构，在2.2 eV处产生直接允许的光学跃迁，小于氧化物带隙值的一半。这些发现促使人们进一步探索这种材料的可见光响应，据预测，该材料在很宽的电化学电势范围内都是稳定的。

更新日期：2017-12-11

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