Koopmans Marten, Leiviskä Miina A T, Liu Jian, Dong Jingjin, Qiu Li, Hummelen Jan C, Portale Giuseppe, Heiber Michael C, Koster L Jan Anton
Zernike Institute for Advanced Materials, University of Groningen, Groningen 9747 AG, The Netherlands.
Stratingh Institute for Chemistry, University of Groningen, Groningen 9747 AG, The Netherlands.
ACS Appl Mater Interfaces. 2020 Dec 16;12(50):56222-56230. doi: 10.1021/acsami.0c15490. Epub 2020 Dec 2.
High electrical conductivity is a prerequisite for improving the performance of organic semiconductors for various applications and can be achieved through molecular doping. However, often the conductivity is enhanced only up to a certain optimum doping concentration, beyond which it decreases significantly. We combine analytical work and Monte Carlo simulations to demonstrate that carrier-carrier interactions can cause this conductivity decrease and reduce the maximum conductivity by orders of magnitude, possibly in a broad range of materials. Using Monte Carlo simulations, we disentangle the effect of carrier-carrier interactions from carrier-dopant interactions. Coulomb potentials of ionized dopants are shown to decrease the conductivity, but barely influence the trend of conductivity versus doping concentration. We illustrate these findings using a doped fullerene derivative for which we can correctly estimate the carrier density at which the conductivity maximizes. We use grazing-incidence wide-angle X-ray scattering to show that the decrease of the conductivity cannot be explained by changes to the microstructure. We propose the reduction of carrier-carrier interactions as a strategy to unlock higher-conductivity organic semiconductors.
高电导率是提升有机半导体在各种应用中性能的先决条件，可通过分子掺杂实现。然而，电导率通常仅在达到某个最佳掺杂浓度之前会增强，超过该浓度后便会显著下降。我们结合分析工作与蒙特卡罗模拟，以证明载流子 - 载流子相互作用会导致这种电导率下降，并使最大电导率降低几个数量级，这可能在广泛的材料中出现。通过蒙特卡罗模拟，我们将载流子 - 载流子相互作用的影响与载流子 - 掺杂剂相互作用区分开来。已表明电离掺杂剂的库仑势会降低电导率，但对电导率与掺杂浓度的关系趋势影响甚微。我们用一种掺杂富勒烯衍生物来说明这些发现，对于该衍生物我们能够正确估计电导率达到最大值时的载流子密度。我们利用掠入射广角X射线散射表明，电导率的下降无法用微观结构的变化来解释。我们提出减少载流子 - 载流子相互作用作为解锁更高电导率有机半导体的一种策略。
