Selective Nanocrystal Synthesis and Calculated Electronic Structure of All Four Phases of Copper-Antimony-Sulfide
Selective Nanocrystal Synthesis and Calculated Electronic Structure of All Four Phases of Copper-Antimony-Sulfide
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DOI：
10.1021/cm5005642
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发表时间：
2014-05-13
影响因子：
8.6
通讯作者：
Gupta, Arunava
中科院分区：
文献类型：
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作者：
Ramasamy, Karthik;Sims, Hunter;Gupta, Arunava
近年来，为了满足对可持续太阳能电池材料的需求，人们研究了各种各样的铜基半导体硫属化物。由无毒和地球丰富的元素组成的一类有吸引力的材料是铜-锑-硫化物。铜-锑-硫化物系统由四个主要相组成，即CuSbS 2（铜锑石）、Cu 12 Sb 4S 13（黝铜矿）、Cu 3SbS 3（Skinnerite）和Cu 3SbS 4（Fematinite）。所有四个相都是p型半导体，具有0.5和2 eV之间的能带隙，具有超过105 cm（-1）的大吸收系数值。我们首次开发了简单的胶体热注入方法，用于纯相合成所有四个相的纳米晶体。Cu 12 Sb 4S 13和Cu 3SbS 3被发现具有直接带隙（分别为1.6和1.4 eV），而其他两相显示间接带隙（CuSbS 2和Cu 3SbS 4分别为1.1和1.2 eV）。合成方法产生不同相具有不同形态的纳米晶体。合成的CuSbS 2为纳米片，Cu 12 Sb 4S 13为中空结构，而Cu 3SbS 3为均匀球形，Cu 3SbS 4为扁球形。为了理解的光学和电学性质，我们已经计算了所有四个阶段的电子结构，使用混合泛函方法（HSE 06）和PBE广义梯度近似密度泛函理论。与实验结果一致，计算表明，CuSbS 2和Cu 3SbS 4是间接带隙材料，但具有略高的带隙值分别为1.6和2.5 eV。类似地，Cu 3SbS 3被确定为具有1.5eV的带隙的直接带隙材料。有趣的是，PBE和HSE 06方法都预测了完全化学计量的Cu 12 Sb 4S 13相中的金属行为，其中带的打开导致具有不同数量的价电子的非化学计量组合物的半导体或绝缘行为。在可见光波长的所有阶段的吸收系数值估计为104和105厘米（-1）之间的范围内，确认其潜在的太阳能转换应用。
A wide variety of copper-based semiconducting chalcogenides have been investigated in recent years to address the need for sustainable solar cell materials. An attractive class of materials consisting of nontoxic and earth abundant elements is the copper-antimony-sulfides. The copper-antimony- sulfide system consists of four major phases, namely, CuSbS2 (Chalcostibite), Cu12Sb4S13 (Tetrahedrite), Cu3SbS3 (Skinnerite), and Cu3SbS4 (Fematinite). All four phases are p-type semiconductors having energy band gaps between 0.5 and 2 eV, with reported large absorption coefficient values over 105 cm(-1). We have for the first time developed facile colloidal hot-injection methods for the phase-pure synthesis of nanocrystals of all four phases. Cu12Sb4S13 and Cu3SbS3 are found to have direct band gaps (1.6 and 1.4 eV, respectively), while the other two phases display indirect band gaps (1.1 and 1.2 eV for CuSbS2 and Cu3SbS4, respectively). The synthesis methods yield nanocrystals with distinct morphology for the different phases. CuSbS2 is synthesized as nanoplates, and Cu12Sb4S13 is isolated as hollow structures, while uniform spherical Cu3SbS3 and oblate spheroid nanocrystals of Cu3SbS4 are obtained. In order to understand the optical and electrical properties, we have calculated the electronic structures of all four phases using the hybrid functional method (HSE 06) and PBE generalized gradient approximation to density functional theory. Consistent with experimental results, the calculations indicate that CuSbS2 and Cu3SbS4 are indirect band gap materials but with somewhat higher band gap values of 1.6 and 2.5 eV, respectively. Similarly, Cu3SbS3 is determined to be a direct band gap material with a gap of 1.5 eV. Interestingly, both PBE and HSE06 methods predict metallic behavior in fully stoichiometric Cu12Sb4S13 phase, with opening up of bands leading to semiconducting or insulating behavior for off-stoichiometric compositions with a varying number of valence electrons. The absorption coefficient values at visible wavelengths for all the phases are estimated to range between 104 and 105 cm(-1), confirming their potential for solar energy conversion applications.