Department of Electrical and Computer Engineering, University of Toronto, 10 King's College Road, Toronto, Ontario M5S 3G4, Canada.
ACS Nano. 2012 Sep 25;6(9):8448-55. doi: 10.1021/nn303364d. Epub 2012 Sep 7.
We present a framework--validated using both modeling and experiment--to predict doping in CQD films. In the ionic semiconductors widely deployed in CQD films, the framework reduces to a simple accounting of the contributions of the oxidation state of each constituent, including both inorganic species and organic ligands. We use density functional theory simulations to confirm that the type of doping can be reliably predicted based on the overall stoichiometry of the CQDs, largely independent of microscopic geometrical bonding configurations. Studies employing field-effect transistors constructed from CQDs that have undergone various chemical treatments, coupled with Rutherford backscattering and X-ray photoelectron spectroscopy to provide compositional analysis, allow us to test and confirm the proposed model in an experimental framework. We investigate both p- and n-type electronic doping spanning a wide range of carrier concentrations from 10(16) cm(-3) to over 10(18) cm(-3), and demonstrate reversible switching between p- and n-type doping by changing the CQD stoichiometry. We show that the summation of the contributions from all cations and anions within the film can be used to predict accurately the majority carrier type. The findings enable predictable control over majority carrier concentration via tuning of the overall stoichiometry.
我们提出了一个框架——通过建模和实验进行了验证——来预测 CQD 薄膜中的掺杂。在 CQD 薄膜中广泛应用的离子半导体中，该框架简化为对每个组成部分的氧化态的贡献的简单计算，包括无机物种和有机配体。我们使用密度泛函理论模拟来确认，可以根据 CQDs 的总体化学计量比，很大程度上独立于微观几何键合构型，可靠地预测掺杂类型。使用经过各种化学处理的 CQDs 构建的场效应晶体管的研究，结合卢瑟福背散射和 X 射线光电子能谱分析提供的组成分析，使我们能够在实验框架中测试和验证所提出的模型。我们研究了从 10(16)cm(-3)到超过 10(18)cm(-3)的广泛载流子浓度范围内的 p 型和 n 型电子掺杂，并通过改变 CQD 化学计量比来演示在 p 型和 n 型掺杂之间的可逆转换。我们表明，薄膜中所有阳离子和阴离子的贡献之和可用于准确预测多数载流子类型。这一发现使通过整体化学计量比的调整来实现对多数载流子浓度的可预测控制成为可能。
