Chemical doping controls the electronic properties of organic semiconductors, but so far, doping protocols and mechanisms are less developed than in conventional semiconductors. Here we describe a unique, site-specific, n-type surface doping mechanism for single crystals of two benchmark organic semiconductors that produces dramatic improvement in electron transport and provides unprecedented evidence for doping-induced space charge. The surface doping chemistry specifically targets crystallographic step edges, which are known electron traps, simultaneously passivating the traps and releasing itinerant electrons. The effect on electron transport is profound: field-effect electron mobility increases by as much as a factor of ten, and its temperature-dependent behaviour switches from thermally activated to band-like. Our findings suggest new site-specific strategies to dope organic semiconductors that differ from the conventional redox chemistry of randomly distributed substitutional impurities. Critically, they also verify the presence of doping-induced electron atmospheres, confirming long-standing expectations for organic systems from conventional solid-state theory.

化学掺杂控制有机半导体的电子特性，但到目前为止，掺杂协议和机制不如传统半导体发达。在这里，我们描述了一种独特的、特定位置的、n 型表面掺杂机制，用于两种基准有机半导体的单晶，它显着改善了电子传输，并为掺杂引起的空间电荷提供了前所未有的证据。表面掺杂化学专门针对晶体阶梯边缘，即已知的电子陷阱，同时钝化陷阱并释放流动电子。对电子传输的影响是深远的：场效应电子迁移率增加了多达 10 倍，并且其与温度相关的行为从热激活转变为带状。我们的研究结果提出了新的位点特定策略来掺杂有机半导体，这与随机分布的取代杂质的常规氧化还原化学不同。至关重要的是，他们还验证了掺杂诱导电子气氛的存在，证实了传统固态理论对有机系统的长期期望。