论文标题
二元纳米晶固体中的渗透电荷转运
Percolative Charge Transport In Binary Nanocrystal Solids
论文作者
论文摘要
我们模拟了跨直径为6.5nm和5.1nm的PBSE NC的二元纳米晶体固体（BNS）。我们使用分层纳米颗粒传输模拟器提示来对这些BNSS中的传输进行建模。迁移率在大NC分数F_LNC = 0.25时表现出最小值。迁移率最小为t = 80k，在t = 300k时部分平滑。我们解释了这一点，如下所示。随着LNC级分F_LNC从零开始生长，少数LNC充当横穿BNS的电子的陷阱，因为它们的相关能级较低。因此，增加这些陷阱的F_LNC浓度会降低迁移率。随着f_lnc的增加到达渗透阈值F_LNC = f_p，LNC会形成样品跨度网络，使电子能够通过这些渗透LNC网络遍历整个BNS。随着F_LNC的生长，通过不断增长的渗透LNC网络运输驱动移动性的快速增长。因此，电子迁移率表现出明显的最小值作为f_lnc的函数，以f_lnc = f_p为中心。随着电子密度的增加，迁移率的位置最小移至较大的LNC级分。我们已经研究了这种迁移率最低的趋势，这些趋势是温度，电子密度，充电能量，配体长度和无序的趋势。我们通过“重新归一化的陷阱模型”来解释趋势，其中捕获电子将深的LNC陷阱重归于浅层陷阱或动力学障碍物，具体取决于充电能量。我们通过构建和分析BNS移动电子的热图来验证了这种物理图片。
We simulated electron transport across a binary nanocrystal solid (BNS) of PbSe NCs with diameters of 6.5nm and 5.1nm. We used our Hierarchical Nanoparticle Transport Simulator HINTS to model the transport in these BNSs. The mobility exhibits a minimum at a Large-NC-fraction f_LNC=0.25. The mobility minimum is deep at T=80K and partially smoothed at T=300K. We explain this minimum as follows. As the LNC fraction f_LNC starts growing from zero, the few LNCs act as traps for the electrons traversing the BNS because their relevant energy level is lower. Therefore, increasing the f_LNC concentration of these traps decreases the mobility. As increasing f_LNC reaches the percolation threshold f_LNC=f_p, the LNCs form sample-spanning networks that enable electrons to traverse the entire BNS via these percolating LNC networks. Transport through the growing percolating LNC networks drives the rapid growth of the mobility as f_LNC grows past f_p. Therefore, the electron mobility exhibits a pronounced minimum as a function of f_LNC, centered at f_LNC=f_p. The position of the mobility minimum shifts to larger LNC fractions as the electron density increases. We have studied the trends of this mobility minimum with temperature, electron density, charging energy, ligand length, and disorder. We account for the trends by a "renormalized trap model", in which capturing an electron renormalizes a deep LNC trap into a shallow trap or a kinetic obstacle, depending on the charging energy. We verified this physical picture by constructing and analyzing heat maps of the mobile electrons in the BNS.
