(Photo)physical Properties of New Molecular Glasses End-Capped with Thiophene Rings Composed of Diimide and Imine Units.

Marzena Grucela-Zajac,Henryk Janeczek,Katarzyna Bijak,Lukasz Skorka,Kurt Hingerl,Natalia Nosidlak,Jacek Gasiorowski,Michal Filapek,Gabriela Lewinska,Jerzy Sanetra,Ewa Schab-Balcerzak,Malgorzata Wiacek,Niyazi Serdar Sariciftci,Slawomir Kula

doi:10.1021/jp501168b

Abstract

New symmetrical arylene bisimide derivatives formed by using electron-donating–electron-accepting systems were synthesized. They consist of a phthalic diimide or naphthalenediimide core and imine linkages and are end-capped with thiophene, bithiophene, and (ethylenedioxy)thiophene units. Moreover, polymers were obtained from a new diamine, N,N′-bis(5-aminonaphthalenyl)naphthalene-1,4,5,8-dicarboximide and 2,5-thiophenedicarboxaldehyde or 2,2′-bithiophene-5,5′-dicarboxaldehyde. The prepared azomethine diimides exhibited glass-forming properties. The obtained compounds emitted blue light with the emission maximum at 470 nm. The value of the absorption coefficient was determined as a function of the photon energy using spectroscopic ellipsometry. All compounds are electrochemically active and undergo reversible electrochemical reduction and irreversible oxidation processes as was found in cyclic voltammetry and differential pulse voltammetry (DPV) studies. They exhibited a low electrochemically (DPV) calculated energy band gap (Eg) from 1.14 to 1.70 eV. The highest occupied molecular orbital and lowest unoccupied molecular orbital levels and Eg were additionally calculated theoretically by density functional theory at the B3LYP/6-31G(d,p) level. The photovoltaic properties of two model compounds as the active layer in organic solar cells in the configuration indium tin oxide/poly(3,4-(ethylenedioxy)thiophene):poly(styrenesulfonate)/active layer/Al under an illumination of 1.3 mW/cm2 were studied. The device comprising poly(3-hexylthiophene) with the compound end-capped with bithiophene rings showed the highest value of Voc (above 1 V). The conversion efficiency of the fabricated solar cell was in the range of 0.69–0.90%.

Highlights

During the past few decades, processable organic semiconductors, such as small molecules and conjugated polymers, have been intensively studied because of the easy tenability of optical and electrical properties by chemical synthesis
New compounds consisting of a phthalic diimide or naphthalenediimide core end-capped with thiophene, bithiophene, andthiophene units were synthesized
The resulting absorption coefficients revealed a strong correlation with the Article chemical structure of the presented polymers

Summary

Introduction

During the past few decades, processable organic semiconductors, such as small molecules and conjugated polymers, have been intensively studied because of the easy tenability of optical and electrical properties by chemical synthesis. They are attractive for their potential applicability in the fabrication of different types of electronic devices, e.g., light-emitting diodes (LEDs), photodiodes (PDs), photovoltaic cells (PCs), or field effect transistors (FETs).[1−3] remarkable progress has been made, the development of highly efficient and long-term stable optical and electrical devices is still a challenge.

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