Yiu Wai Kin, Mackenzie Lewis, Wilkinson Dylan, Giza Marcin, Vella Benjamin, Cariello Michele, Sproules Stephen, Cooke Graeme, Docampo Pablo
School of Chemistry, University of Glasgow, Glasgow, G12 8QQ, UK.
Phys Chem Chem Phys. 2025 Jun 5;27(22):11898-11906. doi: 10.1039/d5cp00828j.
Achieving effective doping in n-type organic molecular charge transport materials is critical for the development of high-performance optoelectronic devices. However, the role of side-chains in doping reactions remains incompletely understood in some systems. This study focuses on naphthalenediimide (NDI) derivatives, which offer simple synthetic protocols and potentially lower costs compared to traditional fullerene-derived materials. In particular, we explore two functionalised NDI derivatives, comparing one with polar ethylene glycol side-chains (NDI-G) to a non-polar variant with branched alkyl side-chains (NDI-EtHx). Our results show that the effectiveness and speed of the doping reaction with (4-(1,3-dimethyl-2,3-dihydro-1-benzoimidazol-2-yl)phenyl)dimethylamine (N-DMBI) is much higher with the more polar NDI-G derivative. We postulate that this arises partly from the closer interactions between the dopant and the NDI molecule, facilitated by the polar glycol side-chains. As a result, thin films reach conductivities exceeding 10 S cm. We additionally demonstrate their incorporation into efficient perovskite solar cells, demonstrating the effectiveness of the doping process. We investigate this process with a combination of spectroscopy and density functional theory (DFT) modelling, showing that a complex is likely formed between the resulting N-DMBI cation and the NDI radical anion which then promotes electron transfer to a neutral NDI molecule, thereby generating free charge in the film. These findings underscore the importance of synthetic design on the doping behaviour, with the incorporation of ethylene glycol side-chains emerging as an effective strategy to achieve better electrical conductivity for NDI based systems.
在n型有机分子电荷传输材料中实现有效的掺杂对于高性能光电器件的发展至关重要。然而，在某些体系中，侧链在掺杂反应中的作用仍未被完全理解。本研究聚焦于萘二亚胺（NDI）衍生物，与传统的富勒烯衍生材料相比，它们具有简单的合成方案且成本可能更低。特别是，我们探索了两种功能化的NDI衍生物，将一种带有极性乙二醇侧链的（NDI-G）与一种带有支链烷基侧链的非极性变体（NDI-EtHx）进行比较。我们的结果表明，对于极性更强的NDI-G衍生物，与（4-(1,3-二甲基-2,3-二氢-1-苯并咪唑-2-基)苯基）二甲胺（N-DMBI）的掺杂反应的有效性和速度要高得多。我们推测这部分源于掺杂剂与NDI分子之间更紧密的相互作用，这是由极性二醇侧链促成的。结果，薄膜的电导率超过10 S cm。我们还展示了它们在高效钙钛矿太阳能电池中的应用，证明了掺杂过程的有效性。我们结合光谱学和密度泛函理论（DFT）建模对这一过程进行了研究，结果表明，生成的N-DMBI阳离子与NDI自由基阴离子之间可能形成复合物，然后促进电子转移到中性NDI分子上，从而在薄膜中产生自由电荷。这些发现强调了合成设计对掺杂行为的重要性，引入乙二醇侧链成为实现基于NDI体系更好导电性的有效策略。
