Photoswitching of an n-Type Organic Field Effect Transistor by a Reversible Photochromic Reaction in the Dielectric Film

Abstract

We report on an organic field effect transistor (OFET) with a photochromic dielectric layer, operating as an opto-electrical switch device. The structure contained a photochromic material dissolved in the polymer dielectric layer. The photochromic material was spiropyran exhibiting a large difference of the dipole moments of the stable and metastable forms; poly(methyl methacrylate) was a polymeric insulator; and an n-type perylene derivative was used as the organic semiconductor. Illumination of the structure with UV light resulted in a reversible increase of the source-drain current, accompanied by a reversible decrease of the threshold voltage. The initial parameters were restored by a thermal relaxation in the dark or by illumination with visible light. The photoswitching ratio was found to be dependent on the gate voltage ranging between ca. 2 just above the threshold voltage and ca. 1.3 at the highest voltage employed (90 V). The switching has been attributed to reversible changes of dielectric properties of OFET's insulator (dielectric layer) due to a reversible light-triggered reaction of polar photochromic species, dissolved in the bulk of the dielectric layer. The contribution of dipoles aggregated on the semiconductordielectric interface was estimated to be negligible at gate voltages exceeding ca. 10 V.

Highly UV‐Sensitive and Responsive Benzothiophene/Dielectric Polymer Blend‐Based Organic Thin‐Film Phototransistor

“…Materials : Small molecule semiconductor 2,7-dipentylbenzo[b]-benzo [4,5]thieno [2,3]thiophene (BTBT-C5) was synthesized following procedures in refs. [ 38 ] and [ 39 ] .…”

“…This development reached the point where OTFTs are successfully applied for electronic fl exible paper, OLED fl exible displays, wileyonlinelibrary.com molecules capable of undergoing a photoisomerization, electrons exchange (redox reactions), dissociation, and intramolecular group transfer upon illumination with UV light and reversely by visible light or heat. [ 3,18 ] Major methods to achieve optically controlled OTFT's include doping the active channel material, [ 19 ] modifying the interface of the dielectric/semiconductor [ 20 ] or semiconductor/source-drain, [ 21 ] and blending a photochromic material into the dielectric. [ 22 ] Changes in the molecular dipole moment associated with photoisomerization upon light irradiation result in generation of an additional electric fi eld that modulated a drain current and threshold voltage.…”

“…[ 1,2 ] Performance of OTFTs has been significantly improved in the last decade through engineering of the materials, interfaces, and architecture of devices. [3][4][5] Reported maximum charge carrier mobilities reached 17.2 cm 2 V −1 s −1 for vacuum-deposited asymmetric tridecyl (C 13 )-substituted [1]benzothieno [3,2-b][1]benzothiophene (C 13 -BTBT), [ 6 ] 31.3 cm 2 V −1 s −1 [ 7 ] and 43 cm 2 V −1 s −1 [ 8 ] for solution-processed OTFTs based on symmetric C 8 -BTBT, and 10.5 cm 2 V −1 s −1 for solution-processed conductive polymers. [ 9 ] Compared to the FETs made from the amorphous silicon (α-Si) that have a mobility of ≈1 cm 2 V −1 s −1 , these results are very promising for the massive commercialization of OTFTs.…”

OFET‐Based Memory Devices Operating via Optically and Electrically Modulated Charge Separation between the Semiconductor and 1,2‐bis(Hetaryl)ethene Dielectric Layers

“…[23][24][25][26][27] The latter approach seems to be the most promising. It is known that the highest density of charge carriers in operating OFET fl ows in a few molecular layers of semiconductor adjacent to dielectric.…”

Hybrid Organic/Photochromic Approaches to Generate Multifunctional Materials, Interfaces, and Devices

“…A similar approach to introduce controlled deep trapping levels by using a layer of thermally evaporated DAEs (instead of SPs) at the pentacene/PMMA interface was employed by Yoshida et al [216]. In their [217]. The active layer is an n-type semiconductor (PTCDI-C 13 H 27 ).…”