Perovskite oxides for visible-light-absorbing ferroelectric and photovoltaic materials
Perovskite oxides for visible-light-absorbing ferroelectric and photovoltaic materials
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DOI：
10.1038/nature12622
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发表时间：
2013-11-28
期刊：
影响因子：
64.8
通讯作者：
Rappe, Andrew M.
中科院分区：
文献类型：
--
作者：
Grinberg, Ilya;West, D. Vincent;Rappe, Andrew M.
铁电材料最近作为一类候选材料引起了人们的注意，用于光伏器件，以及光吸收与其他功能特性的耦合(1-7)。在这些材料中，自发电极化引起的强反转对称破缺促进了光激载流子的理想分离，并允许高于带隙的电压，这可能使效率超过传统p-n结太阳能电池(2，6，8-10)的最大可能。铁电氧化物在广泛的机械、化学和热条件下也是稳定的，可以使用低成本的方法来制备，如溶胶-凝胶薄膜沉积和溅射(3，5)。最近的工作(3，5，11)表明，减小铁电层厚度和合理设计电畴结构和铁电-电极界面可以极大地增加从铁电吸收材料获得的电流，将功率转换效率从约10(-4)%提高到约0.5%。铁电氧化物的带隙很宽(2.7-4电子伏特)，只允许使用8%-20%的太阳光谱，这阻碍了光伏效率的进一步提高。在这里，我们描述了一系列由低成本和无毒元素用传统的固态方法制成的单相固体氧化物溶液：[KNbO_3](1-x)[BaNi1/2Nb1/2O_3-Delta](X)(KBNNO)。这些氧化物既表现出铁电性，又表现出在1.1-3.8电子伏特范围内直接带隙的广泛变化。特别是，x=0.1的组分在室温下是极性的，具有1.39电子伏特的直接带隙，并且具有大约50倍于经典铁电(Pb，La)(Zr，Ti)O-3材料的光电流密度。KBNNO吸收太阳能的能力是目前铁电材料的三到六倍，这表明它是一条可行的铁电半导体电池的途径，用于太阳能转换和其他应用。
Ferroelectrics have recently attracted attention as a candidate class of materials for use in photovoltaic devices, and for the coupling of light absorption with other functional properties(1-7). In these materials, the strong inversion symmetry breaking that is due to spontaneous electric polarization promotes the desirable separation of photo-excited carriers and allows voltages higher than the bandgap, which may enable efficiencies beyond the maximum possible in a conventional p-n junction solar cell(2,6,8-10). Ferroelectric oxides are also stable in a wide range of mechanical, chemical and thermal conditions and can be fabricated using low-cost methods such as sol-gel thin-film deposition and sputtering(3,5). Recent work(3,5,11) has shown how a decrease in ferroelectric layer thickness and judicious engineering of domain structures and ferroelectric-electrode interfaces can greatly increase the current harvested from ferroelectric absorber materials, increasing the power conversion efficiency from about 10(-4) to about 0.5 per cent. Further improvements in photovoltaic efficiency have been inhibited by the wide bandgaps (2.7-4 electronvolts) of ferroelectric oxides, which allow the use of only 8-20 per cent of the solar spectrum. Here we describe a family of single-phase solid oxide solutions made from low-cost and non-toxic elements using conventional solid-state methods: [KNbO3](1-x)[BaNi1/2Nb1/2O3-delta](x) (KBNNO). These oxides exhibit both ferroelectricity and a wide variation of direct bandgaps in the range 1.1-3.8 electronvolts. In particular, the x = 0.1 composition is polar at room temperature, has a direct bandgap of 1.39 electronvolts and has a photocurrent density approximately 50 times larger than that of the classic ferroelectric (Pb,La)(Zr,Ti)O-3 material. The ability of KBNNO to absorb three to six times more solar energy than the current ferroelectric materials suggests a route to viable ferroelectric semiconductor-based cells for solar energy conversion and other applications.