Electronic structures and optical characteristics of fluorescent pyrazinoquinoxaline assemblies and Au interfaces

Soyeong Kwon,Dong Yeun Jeong,Kyungju Noh,Taeyoung Choi,Dong-Wook Kim,Youngmin You,Weon-Sik Chae,P Devi,Luciano Colazzo

doi:10.1038/s41598-021-96437-x

Abstract

Understanding the excitonic processes at the interfaces of fluorescent π-conjugated molecules and metal electrodes is important for both fundamental studies and emerging applications. Adsorption configurations of molecules on metal surfaces significantly affect the physical characteristics of junctions as well as molecules. Here, the electronic structures and optical properties of molecular assemblies/Au interfaces were investigated using scanning probe and photoluminescence microscopy techniques. Scanning tunneling microscopy images and tunneling conductance spectra suggested that the self-assembled molecules were physisorbed on the Au surface. Visible-range photoluminescence studies showed that Au thin films modified the emission spectra and reduced the lifetime of excitons. Surface potential maps, obtained by Kelvin probe force microscopy, could visualize electron transfer from the molecules to Au under illumination, which could explain the decreased lifetime of excitons at the molecule/Au interface.

Highlights

Understanding the excitonic processes at the interfaces of fluorescent π-conjugated molecules and metal electrodes is important for both fundamental studies and emerging applications
The molecular construct of DY1 involves pyrazinoquinoxaline with four phenyl groups at the 2, 3, 7, and 8 positions
The PL spectrum is characterized with a vibronic spacing of 1040 cm−1

Summary

Introduction

Understanding the excitonic processes at the interfaces of fluorescent π-conjugated molecules and metal electrodes is important for both fundamental studies and emerging applications. Chemical reaction at the organic/metal interfaces can form gap states and pin the Fermi level, which can modify the interfacial electronic s tructures[6,7,8,9]. Scanning tunneling spectroscopy (STS) measurements can visualize the electronic states of molecules on metal s ubstrates[14,15,16,17,18].

Results

Conclusion