Colloidal materials of tin(II) sulfide (SnS), as a layered semiconductor with a narrow band gap, are emerging as a potential alternative to the more toxic metal chalcogenides (PbS, PbSe, CdS, CdSe) for various applications such as electronic and optoelectronic devices. We describe a new and simple pathway to produce colloidal SnS nanosheets with large lateral sizes and controllable thickness, as well as single-crystallinity. The synthesis of the nanosheets is achieved by employing tin(II) acetate as tin precursor instead of harmful precursors such as bis[bis(trimethylsilyl)amino] tin(II) and halogen-involved precursors like tin chloride, which limits the large-scale production. We successfully tuned the morphology between squared nanosheets with lateral dimensions from 150 to about 500 nm and a thickness from 24 to 29 nm, and hexagonal nanosheets with lateral sizes from 230 to 1680 nm and heights ranging from 16 to 50 nm by varying the ligands oleic acid and trioctylphosphine. The formation mechanism of both shapes has been investigated in depth, which is also supported by DFT simulations. The optoelectronic measurements show their relatively high conductivity with a pronounced sensitivity to light, which is promising in terms of photo-switching, photo-sensing, and photovoltaic applications also due to their reduced toxicity.
Transient terahertz photoconductivity measurements of minority-carrier lifetime in tin sulfide thin films: Advanced metrology for an early-stage photovoltaic material
High Performance n- and p-Type Field-Effect Transistors Based on Hybridly Surface-Passivated Colloidal PbS Nanosheets
胶体合成的纳米材料是未来电子器件的有希望的候选材料之一，因为它们的简单性和生产成本低廉。具体而言，胶体纳米片是非常感兴趣的，因为它们可以方便地通过胶体方法生产，同时具有二维的优点。为了采用这些材料，相应的晶体管行为应该是可调节的并且具有高性能。我们表明，胶体硫化铅纳米片的晶体管性能是可调的，通过改变表面钝化，接触金属，或通过将它们暴露在空气中。我们发现，添加卤素离子的合成导致改善的导电性，场效应迁移率，和这些晶体管的开/关比通过钝化它们的表面缺陷。获得了优异的n型特性，场效应迁移率为248 cm ^2 V ^-1 s ^-1，开/关比为4 × 10^6。通过改变接触金属和向工作环境中添加氧气，这些条带的导电性可以从n型变为p型。作为后摩尔时代的可能解决方案，实现胶体材料等新型高质量半导体至关重要。在这方面，我们的研究结果可以提供新的见解，有助于加速其优化潜在的应用。
Computational Design of Mixed-valence Tin Sulfides as Solar Absorbers
二元锡硫化物由于其简单的化学计量和半导体性质而吸引人，并且是潜在的成本有效的光电材料。Sn的多价性允许更多的中间组合物Sn $_x$ S $_y$，其结构和性质是令人感兴趣的。Sn $_2$ S $_3$已经被考虑作为混合价半导体。其他中间成分仍然难以捉摸。本文采用群智能晶体结构搜索方法结合第一性原理能量计算，对Sn $_x$ S $_y$系列化合物的相稳定性进行了全面的研究。我们发现，混合价Sn $_x$ S $_y$化合物分解成纯价SnS和SnS $_2$的稳定性一般弱于Sn $_x$ O $_y$对应物，可能是由于化学键的差异。除了确定实验发现的Sn $_2$ S $_3$的稳定相，我们的计算表明，Sn $_3$ S $_4$相是另一种混合价组合物，其相对于分解成SnS和SnS $_2$显示出边缘稳定性。其他研究的组合物在环境条件下可能是亚稳态的，具有轻微的正形成能力。我们发现两种结构的Sn $_3$ S $_4$具有很低的能量，这两个功能的一维链状碎片通过打破边缘连接的八面体层的SnS $_2$。这两种结构都表明晶格声子的稳定性和一个显示准直接带隙与计算值为1.43 eV，理想的太阳能吸收器。进一步分析的组成-结构-性质的关系支持的概念，低维的锡-S基序和范德华相互作用可能会导致不同的结构类型和化学组成，具有功能的性质，尚未确定的Sn $_x$ S $_y$系列与混合价。
