Photo-Fries-based photosensitive polymeric interlayers for patterned organic devices.

Alberto Montaigne Ramil,Wolfgang Kern,Gerardo Hernandez-Sosa,Günther Schwabegger,Niyazi Serdar Sariciftci,Thomas Griesser,Christian Teichert,Thomas Höfler,Quan Shen,Clemens Simbrunner,Helmut Sitter,Gregor Trimmel

doi:10.1007/s00339-012-6853-2

Abstract

This work reports on the investigation of the photosensitive polymer poly(diphenyl bicyclo[2.2.1]hept-5-ene-2,3-dicarboxylate) (PPNB), which undergoes the photo-Fries rearrangement upon illumination with UV-light, used as interfacial layers in organic electronic devices. Two cases were investigated: the use of a blend of PPNB with poly-vinylcarbazole (PVK) as an interlayer in para-sexiphenyl (PSP) based organic light emitting diodes (OLEDs) and the use of PPNB as gate dielectric layer in organic field effect transistors (OFETs). The photo-Fries rearrangement reaction causes a change of the polymer chemical structure resulting in a change of its physical and chemical properties. The electroluminescence spectra and emission of the PSP OLEDs are not affected when fabricated with a non-UV-illuminated PPNB:PVK blend. However, the electroluminescence is totally quenched in those OLEDs fabricated with UV-illuminated PPNB:PVK blend. Although the dielectric constant of PPNB increases upon UV-treatment, it is demonstrated that those OFETs built with UV-treated PPNB as gate dielectric have lower performance than those OFETs built with non-UV-treated PPNB. Furthermore, the effect of the UV-illumination of PPNB and PPNB:PVK blend on the growth of the small molecules C60 and PSP has been studied by atomic force microscopy. Using photolithography, this kind of photochemistry can be performed to spatially control and tune the optical and electrical performance of organic electronic devices.

Highlights

During the past years, electronic devices based on organic semiconductors attracted much interest within industrial and scientific research
We present the study realized on the use of the polymer PPNB, which undergoes a photoFries rearrangement upon irradiation with UV light, and its blend with poly-vinylcarbazole (PVK) as photosensitive layers in organic field effect transistors (OFETs) and organic light emitting diodes (OLEDs), respectively, built with evaporable small organic molecules as semiconducting active films
The use of PPNB as UV photo sensitive material was tested in OLEDs

Summary

Introduction

Electronic devices based on organic semiconductors attracted much interest within industrial and scientific research. By small change of the surface polarity upon illumination, it was possible to control the grain size of pentacene, and the mobility of charge carriers in the OFETs [21] In this contribution, we present the study realized on the use of the polymer PPNB, which undergoes a photoFries rearrangement upon irradiation with UV light, and its blend with poly-vinylcarbazole (PVK) as photosensitive layers in OFETs and OLEDs, respectively, built with evaporable small organic molecules as semiconducting active films. We chose the small molecule organic semiconductors PSP and C60 as active materials in the presented OLEDs and OFETs, respectively. Both materials and their use in organic devices have been extensively investigated during the last years. As already reported in the literature, mobility values as high as 3 cm V−1 s−1 could be achieved for C60 based n-type OFETs with organic gate dielectrics [34, 35]

Device fabrication

Layer and device characterization

Results and discussion

PPNB as gate dielectric in C60 OFETs

Conclusions