Electric Bistability Induced by Incorporating Self-Assembled Monolayers/aggregated Clusters of Azobenzene Derivatives in Pentacene-Based Thin-Film Transistors

Abstract

Composite films of pentacene and a series of azobenzene derivatives are prepared and used as the active channel material in top-contact, bottom-gate field-effect transistors. The transistors exhibit high field-effect mobility as well as large I-V hysteresis as a function of the gate bias history. The azobenzene moieties, incorporated either in the form of self-assembled monolayer or discrete multilayer clusters at the dielectric surface, result in electric bistability of the pentacene-based transistor either by photoexcitation or gate biasing. The direction of threshold voltage shifts, size of hysteresis, response time, and retention characteristics all strongly depend on the substituent on the benzene ring. The results show that introducing a monolayer of azobenzene moieties results in formation of charge carrier traps responsible for slower switching between the bistable states and longer retention time. With clusters of azobenzene moieties as the trap sites, the switching is faster but the retention is shorter. Detailed film structure analyses and correlation with the transistor/memory properties of these devices are provided.

Perovskite‐Based Phototransistors and Hybrid Photodetectors

“…However, due to the slow release of trapped electrons and the resulting slow recombination of holes and trapped electrons, I DS could keep at high illumination state level without irradiation, indicating the relatively long relaxation time (step 2) in comparison with the rise time (step 1, 0.45 s) as shown in Figure c. As the metastable state could be accelerated by applying negative gate bias, V GS was switched from +30 V to −40 V (step 3) for acceleration of recombination process, and then I DS could be reduced to dark state level after V GS returned back into +30 V (step 4). This phenomenon has offered further potential development of fabricating ultrasensitive 2D perovskite phototransistors or light‐triggered memory devices …”

Visible‐Light Ultrasensitive Solution‐Prepared Layered Organic–Inorganic Hybrid Perovskite Field‐Effect Transistor

“…The device was in a metastable state of high conductivity. The metastable state was mostly likely caused by slow release of the trapped electrons and the resulting slow recombination of holes and trapped electrons, which can be accelerated by applying a negative gate bias . This character makes it possible to manipulate the light‐induced I ds by applying negative gate voltage (Figure b).…”

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

“…The mechanisms that affect OTFT properties based on isomerization of photochromic moieties having EW and ED groups are not fully understood yet. [ 29 ] Here we engineered a UV-responsive blend for the active channel of an OTF-PT by choosing UV-responsive BTBT-C5 semiconductor and a dielectric polymer without photochromic moieties (inert in the UVvis spectrum, i.e., 300-800 nm). With appropriate EW groups acting as the charge trapping sites, we hope to achieve high responsivity and high photosensitivity through enhanced separation of the photogenerated charge carriers at the polymer/ semiconductor interface to increase the charge carrier density.…”