Interdisciplinary Graduate School, ‡Energy Research Institute, §Division of Chemistry and Biological Chemistry, School of Physical and Mathematical Sciences, and ∥School of Material Science and Engineering, Nanyang Technological University , Singapore 639798.
J Am Chem Soc. 2014 May 7;136(18):6684-92. doi: 10.1021/ja501786s. Epub 2014 Apr 24.
Single-phase Cu2ZnSnS4 (CZTS) is an essential prerequisite toward a high-efficiency thin-film solar cell device. Herein, the selective phase formation of single-phase CZTS nanoparticles by ligand control is reported. Surface-enhanced Raman scattering (SERS) spectroscopy is demonstrated for the first time as a characterization tool for nanoparticles to differentiate the mixed compositional phase (e.g., CZTS, CTS, and ZnS), which cannot be distinguished by X-ray diffraction. Due to the superior selectivity and sensitivity of SERS, the growth mechanism of CZTS nanoparticle formation by hot injection is revealed to involve three growth steps. First, it starts with nucleation of Cu(2-x)S nanoparticles, followed by diffusion of Sn(4+) into Cu(2-x)S nanoparticles to form the Cu3SnS4 (CTS) phase and diffusion of Zn(2+) into CTS nanoparticles to form the CZTS phase. In addition, it is revealed that single-phase CZTS nanoparticles can be obtained via balancing the rate of CTS phase formation and diffusion of Zn(2+) into the CTS phase. We demonstrate that this balance can be achieved by 1 mL of thiol with Cu(OAc)2, Sn(OAc)4, and Zn(acac)2 metal salts to synthesize the CZTS phase without the presence of a detectable binary/ternary phase with SERS.
单相 Cu2ZnSnS4（CZTS）是高效薄膜太阳能电池器件的重要前提。本文通过配体控制，实现了单相 CZTS 纳米粒子的选择性相形成。表面增强拉曼散射（SERS）光谱首次被证明是一种用于纳米粒子的表征工具，可以区分混合组成相（例如，CZTS、CTS 和 ZnS），而 X 射线衍射无法区分这些相。由于 SERS 的优越选择性和灵敏度，揭示了通过热注射形成 CZTS 纳米粒子的生长机制涉及三个生长步骤。首先，它始于 Cu(2-x)S 纳米粒子的成核，然后 Sn(4+)扩散到 Cu(2-x)S 纳米粒子中形成 Cu3SnS4（CTS）相，以及 Zn(2+)扩散到 CTS 纳米粒子中形成 CZTS 相。此外，还揭示了通过平衡 CTS 相形成的速率和 Zn(2+)向 CTS 相扩散的速率，可以获得单相 CZTS 纳米粒子。我们证明，通过将 1 mL 巯基与 Cu(OAc)2、Sn(OAc)4 和 Zn(acac)2 金属盐混合，可以在不存在可检测的二元/三元相的情况下，通过 SERS 合成 CZTS 相，实现这种平衡。
