Vol.:(0123456789) 1 3 Journal of Materials Science: Materials in Electronics https://doi.org/10.1007/s10854-020-02986-8 Facile synthesis of naphthalene diimide (NDI) derivatives: aggregation‑induced emission, photophysical and transport properties Neelam Kumari 1,2  · Samya Naqvi 1  · Mehak Ahuja 1,2  · Komal Bhardwaj 1,2  · Rachana Kumar 1,2 Received: 20 October 2019 / Accepted: 24 January 2020 © Springer Science+Business Media, LLC, part of Springer Nature 2020 Abstract Naphthalene diimide (NDI) derivatives have been synthesized via facile synthesis process and comprehensively studied their photophysical, thermal-activated conductivity and electron transport properties. Four diferent substituents at imide nitrogen, i.e. 2,6 diisopropyl phenyl (iPrP-NDI), diphenylmethylene (DPM-NDI), 2-nitrophenyl (NO 2 P-NDI) and pentafuorophenyl (PFP-NDI) have been studied for their efect on self-assembling, photophysical and electronic properties. Electrochemical analysis has been performed to evaluate their redox properties and calculation of HOMO and LUMO energy levels. These NDI derivatives have been analysed for their aggregation behaviour and aggregation-induced emission (AIE) by absorption and emission spectroscopy in fresh and aged solutions in diferent polarity solvents without using any external additive. Among all, NO 2 P-NDI showed strong AIE property in fresh as well as aged samples. Conductivity of NDI derivatives has been measured as a function of temperature where the highest conductivity ~ 10 −4  S −1  cm −1 was obtained at 200 °C in iPrP- NDI. SEM images clearly showed diferent types of assembly formation in solid state for all the materials. All the materials showed excellent electron mobility of the order of 10 −4 to 10 −3  cm 2  V −1  s −1 measured following the standard protocol of SCLC model. Such NDI materials with excellent photophysical and electronic properties are potential candidates to be used as n-type semiconductor material in organic electronics. NO 2 P-NDI which also shows aggregation-induced emission can be used on OLEDs or other bio-medical applications as luminescent material. 1 Introduction Designing new organic molecules with appropriate optical and electronic properties is the demand of the current organic elec- tronic research [1–10]. Naphthalene diimides (NDI) and per- ylene diimides (PDI) have emerged as one of the extensively investigated π-conjugated system due to their attractive opti- cal and electronic properties [11–13]. Naphthalene diimides have drawn much attention due to their high electron afn- ity, good charge mobility, high photoluminescence quantum yields, reversible redox properties, excellent thermal stability, solubility, appropriate self-assembly and oxidative stability [14, 15]. Because of these factors, NDIs are promising candi- date in many potential applications such as organic electronics [14, 16, 17], sensors [18–21] and nanometer materials [22, 23]. NDIs are chemically robust, neutral, planar, redox active, electron-defcient aromatic compounds having high melting points so that they can be widely used in supramolecular archi- tectures, electronic materials and as chromophores. 1,4,5,8 Naphthalene tetra carboxylic dianhydride (NTCDA) is the main precursor for the synthesis of a variety of NDI molecules. Currently, the designing strategy to synthesize NDI derivatives involves functionalization at imide nitrogens and substitution at naphthyl core [24]. Substitution at N-imide position results in weak fuorescing highly soluble NDI materials. These mate- rials show typical absorption characteristics with low Stokes shift due to rigid naphthalene core causing only a slight dif- ference in dipole moment of ground and excited states [25]. However, such molecules have shown strong electron transport Electronic supplementary material The online version of this article (https://doi.org/10.1007/s10854-020-02986-8) contains supplementary material, which is available to authorized users. * Rachana Kumar rachanak.npl@nic.in; rachanasinghchem@gmail.com 1 Advanced Materials and Devices Metrology Division, Photovoltaic Metrology Group, CSIR-National Physical Laboratory, Dr. K. S. Krishnan Marg, New Delhi 110012, India 2 Academy of Scientifc and Innovative Research, HRDG, Ghaziabad, India