Dependence of Carrier Mobility on Nanocrystal Size and Ligand Length in PbSe Nanocrystal Solids
Dependence of Carrier Mobility on Nanocrystal Size and Ligand Length in PbSe Nanocrystal Solids
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DOI：
10.1021/nl101284k
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发表时间：
2010-05-01
期刊：
影响因子：
10.8
通讯作者：
Law, Matt
中科院分区：
文献类型：
--
作者：
Liu, Yao;Gibbs, Markelle;Law, Matt
我们测量了一系列链烷二硫醇处理的PbSe纳米（NC）薄膜的室温电子和空穴场效应迁移率（μ（FE））作为NC尺寸和链烷长度的函数。我们发现，载流子迁移率随着配体长度的增加而呈指数下降，根据标度参数β = 1.08-1.10埃（-1），正如预期的跳跃输运与烷烃隧道势垒的颗粒导体。电子耦合能量高达8毫电子伏的计算从迁移率数据。随着NC直径的增加，迁移率增加1-2个数量级（电子和空穴分别高达0.07和0.03 cm（2）V-1 s（-1））：电子迁移率在NC尺寸接近6 nm时达到峰值，然后随着NC的增大而降低，而空穴迁移率则呈单调增加。的大小流动性的趋势似乎主要是由较小的跳跃数所需的运输通过阵列的较大的NC，但也可能反映了系统的陷阱状态的深度减少，减少NC手间隙。我们发现，载流子迁移率是独立的NC样品的多分散性，这可以理解，如果渗滤网络的较大直径，较小的带隙NC进行这些NC固体中的大部分电流。我们的研究结果建立了一个基线的迁移率趋势在PbSe NC固体，与制造高迁移率NC为基础的光电器件的影响。
We measure the room-temperature electron and hole field-effect mobilities (mu(FE)) of a series of alkanedithiol-treated PbSe nanocrystal (NC) films as a function of NC size and the length of the alkane chain. We find that carrier mobilities decrease exponentially with increasing ligand length according to the scaling parameter beta = 1.08-1.10 angstrom(-1), as expected for hopping transport in granular conductors with alkane tunnel barriers. An electronic coupling energy as large as 8 meV is calculated from the mobility data. Mobilities increase by 1-2 orders of magnitude with increasing NC diameter (up to 0.07 and 0.03 cm(2) V-1 s(-1) for electrons and holes, respectively): the electron mobility peaks at a NC size of similar to 6 nm and then decreases for larger NCs, whereas the hole mobility shows a monotonic increase. The size-mobility trends seem to be driven primarily by the smaller number of hops required for transport through arrays of larger NCs but may also reflect a systematic decrease in the depth of trap states with decreasing NC hand gap. We find that carrier mobility is independent of the polydispersity of the NC samples, which can be understood if percolation networks of the larger-diameter, smaller-band-gap NCs carry most of the current in these NC solids. Our results establish a baseline for mobility trends in PbSe NC solids, with implications for fabricating high-mobility NC-based optoelectronic devices.