Consideration of Azobenzene-Based Self-Assembled Monolayer Deposition Conditions for Maximizing Optoelectronic Switching Performances

Abstract

Photochromic molecules, which change their molecular structure under external stimuli, are promising for increasing the device functionality without consuming additional space. Azobenzene is a typical chromophore that undergoes cis− trans photoisomerization and thus can control the surface dipole moment when applied as a self-assembled monolayer (SAM). A SAM of fluorinated azobenzene (FAZO) is designed for work function tuning of Au by a large dipole moment difference via photoisomerization. For achieving efficient optoelectronic switching, the photoswitching characteristics of FAZO-SAM were investigated according to the processing solvent. Solvents with a higher dielectric constant (ε > 9) could efficiently screen intermolecular electrostatic repulsions and promote the formation of a well-ordered SAM on Au. Interestingly, a well-ordered FAZO-SAM exhibits inefficient photoisomerization because of steric hindrance and/or effective excitonic coupling between adjacent chromophores, while a SAM processed using a marginally polar solvent maximizes the photoswitching efficiency. We present a solvent-based processing protocol of photochromic molecular SAMs to maximize photoelectric switching.

Highly Sensitive and Selective Organic Gas Sensors Based on Nitrided ZSM-5 Zeolite

“…We used UV–vis absorption spectra (Figure c) to evaluate the thicknesses and the changes in crystallinity of the P3HT films with various amounts of zeolite. The UV–vis spectra of P3HT films show similar absorption bands irrespective of the zeolite type. − The thicknesses and ratios of the (0–0) and (0–2) transitions of the P3HT films were calculated from their UV–vis spectra using the Beer–Lambert law. The Bee–Lambert law presents a relationship among the absorbance, molar extinction coefficient (ε), path length ( l ), and concentration ( c ): A = ε lc .…”

Molecular‐Switch‐Embedded Solution‐Processed Semiconductors

“…Based on the theoretical/experimental proof of photoisomerization of these SAM molecules, we recently studied SAM formation methods to maximize the photoprogrammable switching behavior of optoelectronic devices using A14 ( Figure ). [ 212 ] In the UV absorption spectrum, the trans isomers of azobenzene molecules exhibited an intense peak at ≈355 nm in the initial state, which was reduced during UV light exposure. The peak in the region near ≈445 nm increased.…”

Boosting photoprogramming performance of molecular-switch-embedded organic transistors via structural optimization of polymer semiconductors

“…8–14 Embedding photochromic molecular switches such as diarylethenes (DAEs) and azobenzenes into organic field-effect transistors (OFETs) is one of the most efficient ways to realize highly efficient photoprogramming due to the bistable switching of OFET current levels by means of two different external wavelengths. 15–21 This approach has a significant advantage in terms of imparting structural simplicity over strategies involving the use of other organic memory devices such as floating-gate- or electret-based OFETs, because only the channel layer is slightly tuned from a single-component organic semiconductor to an organic semiconductor/molecular switch mixture, while all other constituting layers of OFETs can be the same. 22–27…”