The Center for Photochemical Sciences, Department of Physics, Bowling Green State University, Bowling Green, Ohio 43403, United States.
ACS Nano. 2013 Aug 27;7(8):6964-77. doi: 10.1021/nn402844m. Epub 2013 Aug 2.
One of the key challenges facing the realization of functional nanocrystal devices concerns the development of techniques for depositing colloidal nanocrystals into electrically coupled nanoparticle solids. This work compares several alternative strategies for the assembly of such films using an all-optical approach to the characterization of electron transport phenomena. By measuring excited carrier lifetimes in either ligand-linked or matrix-encapsulated PbS nanocrystal films containing a tunable fraction of insulating ZnS domains, we uniquely distinguish the dynamics of charge scattering on defects from other processes of exciton dissociation. The measured times are subsequently used to estimate the diffusion length and the carrier mobility for each film type within the hopping transport regime. It is demonstrated that nanocrystal films encapsulated into semiconductor matrices exhibit a lower probability of charge scattering than that of nanocrystal solids cross-linked with either 3-mercaptopropionic acid or 1,2-ethanedithiol molecular linkers. The suppression of carrier scattering in matrix-encapsulated nanocrystal films is attributed to a relatively low density of surface defects at nanocrystal/matrix interfaces.
实现功能性纳米晶体器件面临的一个关键挑战是开发将胶体纳米晶体沉积到电耦合纳米颗粒固体中的技术。这项工作比较了几种替代策略，用于使用全光学方法来表征电子输运现象来组装这种薄膜。通过测量含有可调谐绝缘 ZnS 域分数的配体连接或基质封装 PbS 纳米晶体薄膜中的激发载流子寿命，我们独特地区分了电荷在缺陷上散射的动力学与激子离解的其他过程。随后，使用所测量的时间来估计每个薄膜类型在跳跃输运区域中的扩散长度和载流子迁移率。结果表明，封装在半导体基质中的纳米晶体薄膜比用 3-巯基丙酸或 1,2-乙二硫醇分子链接器交联的纳米晶体固体具有更低的电荷散射概率。基质封装纳米晶体薄膜中载流子散射的抑制归因于纳米晶体/基质界面处表面缺陷的相对低密度。
