Instituto de Energía Solar, Univ. Politécnica de Madrid, Ciudad Universitaria s/n, 28040 Madrid, Spain.
Phys Chem Chem Phys. 2011 Dec 7;13(45):20401-7. doi: 10.1039/c1cp22664a. Epub 2011 Oct 13.
Intermediate band materials can boost photovoltaic efficiency through an increase in photocurrent without photovoltage degradation thanks to the use of two sub-bandgap photons to achieve a full electronic transition from the valence band to the conduction band of a semiconductor structure. After having reported in previous works several transition metal-substituted semiconductors as able to achieve the electronic structure needed for this scheme, we propose at present carrying out this substitution in sulfides that have bandgaps of around 2.0 eV and containing octahedrally coordinated cations such as In or Sn. Specifically, the electronic structure of layered SnS(2) with Sn partially substituted by vanadium is examined here with first principles quantum methods and seen to give favourable characteristics in this respect. The synthesis of this material in nanocrystalline powder form is then undertaken and achieved using solvothermal chemical methods. The insertion of vanadium in SnS(2) is found to produce an absorption spectrum in the UV-Vis-NIR range that displays a new sub-bandgap feature in agreement with the quantum calculations. A photocatalytic reaction-based test verifies that this sub-bandgap absorption produces highly mobile electrons and holes in the material that may be used for the solar energy conversion, giving experimental support to the quantum calculations predictions.
中间带材料可以通过增加光电流而不降低光电压来提高光伏效率，这要归功于使用两个亚带隙光子从半导体结构的价带全电子跃迁到导带。在之前的工作中，我们已经报道了几种过渡金属取代的半导体能够实现该方案所需的电子结构，目前我们建议在带隙约为 2.0 eV 的硫化物中进行这种取代，其中包含八面体配位的阳离子，如 In 或 Sn。具体来说，本文通过第一性原理量子方法研究了具有部分 V 取代 Sn 的层状 SnS(2)的电子结构，并发现其在这方面具有有利的特性。然后采用溶剂热化学方法合成了这种纳米晶粉末形式的材料。发现 V 插入 SnS(2)会在 UV-Vis-NIR 范围内产生吸收光谱，该光谱显示与量子计算一致的新亚带隙特征。基于光催化反应的测试验证了这种亚带隙吸收在材料中产生了高度迁移的电子和空穴，可用于太阳能转换，为量子计算预测提供了实验支持。
