Electron Transport in Naphthalene Diimide Derivatives

Arkadiusz Selerowicz,Paulina Maczugowska,Jaroslaw Jung,Renata Rybakiewicz-Sekita,Anna Stefaniuk-Grams,Krzysztof Halagan,Malgorzata Zagorska

doi:10.3390/ma14144026

Abstract

Two naphthalene diimides derivatives containing two different (alkyl and alkoxyphenyl) N-substituents were studied, namely, N,N′-bis(sec-butyl)-1,4,5,8-naphthalenetetracarboxylic acid diimide (NDI-s-Bu) and N,N′-bis(4-n-hexyloxyphenyl)-1,4,5,8-naphthalenetetracarboxylic acid diimide (NDI-4-n-OHePh). These compounds are known to exhibit electron transport due to their electron-deficient character evidenced by high electron affinity (EA) values, determined by electrochemical methods and a low-lying lowest unoccupied molecular orbital (LUMO) level, predicted by density functional theory (DFT) calculations. These parameters make the studied organic semiconductors stable in operating conditions and resistant to electron trapping, facilitating, in this manner, electron transport in thin solid layers. Current–voltage characteristics, obtained for the manufactured electron-only devices operating in the low voltage range, yielded mobilities of 4.3 × 10−4 cm2V−1s−1 and 4.6 × 10−6 cm2V−1s−1 for (NDI-s-Bu) and (NDI-4-n-OHePh), respectively. Their electron transport characteristics were described using the drift–diffusion model. The studied organic semiconductors can be considered as excellent candidates for the electron transporting layers in organic photovoltaic cells and light-emitting diodes

Highlights

Arylene diimides, studied over 100 years [1,2], in the past century were predominantly used as dyes and pigments
In view of any application of organic semiconductors in devices exploiting the transport of n-type charge carriers, the electron affinity (EA) value and the position of the lowest unoccupied molecular orbital (LUMO) level, related to each other via Koopmans theorem, are of crucial importance
The obtained EA values indicate that NDI-4-n-OHePh molecules are better electron acceptors than oxygen traps, whereas NDI-s-Bu ones are on the borderline [23,24]

Summary

Introduction

Arylene diimides, studied over 100 years [1,2], in the past century were predominantly used as dyes and pigments (for example, [3,4,5]). They are characterized by the high diversity of their optical properties since their absorption spectra can be tuned either via increasing their aromatic core size or through functionalization with appropriate substituents. They can be used as luminophores [6]. Redox and electronic properties of arylene diimides can be tuned through N-functionalization, albeit to a lesser extent [14,15]

Methods

Results

Conclusion