Enhanced intrinsic photovoltaic effect in tungsten disulfide nanotubes
Enhanced intrinsic photovoltaic effect in tungsten disulfide nanotubes
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DOI：
10.1038/s41586-019-1303-3
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发表时间：
2019-06
期刊：
影响因子：
64.8
通讯作者：
Yijin Zhang;Yijin Zhang;T. Ideue;M. Onga;Feng Qin;R. Suzuki;Alla Zak;R. Tenne;J. H. Smet-J.-H.-S
中科院分区：
文献类型：
--
作者：
Yijin Zhang;Yijin Zhang;T. Ideue;M. Onga;Feng Qin;R. Suzuki;Alla Zak;R. Tenne;J. H. Smet-J.-H.-S
传统p-n结中的光伏效应——其中p型材料（具有过量的空穴）毗邻ann型材料（具有过量的电子）——涉及光诱导的电子空穴对的产生及其随后的分离，从而产生电流。这种光伏效应对于环境友好的能量收集尤为重要，其效率已大幅提高，几乎达到理论极限。通过利用体光伏效应（BPVE）预计会取得进一步的进展，该效应不需要结并且仅发生在反演对称性破缺的晶体中。然而，BPVE 的实际实施因其现有材料的低效率而受到阻碍。维度降低或带隙更小的半导体被认为效率更高。过渡金属二硫属化物 (TMD) 是典型的小带隙二维半导体，通过打破其块体晶体固有的反演对称性，观察到了各种效应，但 BPVE 尚未得到研究。在此，我们报告了基于二硫化钨（TMD 家族成员）的器件中发现的 BPVE。我们发现，系统地降低晶体对称性而不仅仅是破缺的反演对称性——从二维单层转变为具有极性特性的纳米管——极大地增强了 BPVE。由此产生的光电流密度比其他 BPVE 材料大几个数量级。我们的研究结果不仅强调了基于 TMD 的纳米材料的潜力，而且更普遍地强调了晶体对称性降低在提高太阳能转化为电能的效率方面的重要性。
The photovoltaic effect in traditionalp–njunctions—where ap-type material (with an excess of holes) abuts ann-type material (with an excess of electrons)—involves the light-induced creation of electron–hole pairs and their subsequent separation, generating a current. This photovoltaic effect is particularly important for environmentally benign energy harvesting, and its efficiency has been increased dramatically, almost reaching the theoretical limit. Further progress is anticipated by making use of the bulk photovoltaic effect (BPVE), which does not require a junction and occurs only in crystals with broken inversion symmetry. However, the practical implementation of the BPVE is hampered by its low efficiency in existing materials, , , , , –. Semiconductors with reduced dimensionality or a smaller bandgap,have been suggested to be more efficient. Transition-metal dichalcogenides (TMDs) are exemplary small-bandgap, two-dimensional semiconductors,in which various effects have been observed by breaking the inversion symmetry inherent in their bulk crystals, –, but the BPVE has not been investigated. Here we report the discovery of the BPVE in devices based on tungsten disulfide, a member of the TMD family. We find that systematically reducing the crystal symmetry beyond mere broken inversion symmetry—moving from a two-dimensional monolayer to a nanotube with polar properties—greatly enhances the BPVE. The photocurrent density thus generated is orders of magnitude larger than that of other BPVE materials. Our findings highlight not only the potential of TMD-based nanomaterials, but also more generally the importance of crystal symmetry reduction in enhancing the efficiency of converting solar to electric power.