Organic Field-Effect Transistors as Flexible, Tissue-Equivalent Radiation Dosimeters in Medical Applications

Radiation therapy is one of the most prevalent procedures for cancer treatment, but the risks of malignancies induced by peripheral beam in healthy tissues surrounding the target is high. Therefore, being able to accurately measure the exposure dose is a critical aspect of patient care. Here a radiation detector based on an organic field‐effect transistor (RAD‐OFET) is introduced, an in vivo dosimeter that can be placed directly on a patient\u27s skin to validate in real time the dose being delivered and ensure that for nearby regions an acceptable level of low dose is being received. This device reduces the errors faced by current technologies in approximating the dose profile in a patient\u27s body, is sensitive for doses relevant to radiation treatment procedures, and robust when incorporated into conformal large‐area electronics. A model is proposed to describe the operation of RAD‐OFETs, based on the interplay between charge photogeneration and trapping

Isothermal crystallization and time-temperature-transformation diagram of the organic semiconductor 5,11-bis(triethylsilylethynyl)anthradithiophene

Thermal annealing of organic semiconductors is critical for optimization of their electronic properties. The selection of the optimal annealing temperature -often done on a trial-and-error basis- is essential for achieving the most desired micro/nanostructure. While classical materials science relies on time-temperature-transformation (TTT) diagrams to predict such processing-structure relationships, this type of approach is yet to find widespread application in the field of organic electronics. In this work, we constructed a TTT diagram for crystallization of the widely studied organic semiconductor 5,11-bis(triethylsilylethynyl)anthradithiophene (TES-ADT) from its melt. Thermal analysis in the form of isothermal crystallization experiments showed distinctly different types of behaviour depending on the annealing temperature, in agreement with classical crystal nucleation and growth theory. Hence, the TTT diagram correlates with the observed variation in the number of crystal domains, the crystal coverage and film texture as well as the obtained polymorph. As a result, we are able to rationalize the influence of the annealing temperature on the charge-carrier mobility extracted from field-effect transistor (FET) measurements. Evidently, the use of TTT diagrams is a powerful tool to describe structure formation of organic semiconductors and can be used to predict processing protocols that lead to optimal device performance

Solution-Processed Organic and Halide Perovskite Transistors on Hydrophobic Surfaces

Solution-processable electronic devices are highly desirable due to their low cost and compatibility with flexible substrates. However, they are often challenging to fabricate due to the hydrophobic nature of the surfaces of the constituent layers. Here, we use a protein solution to modify the surface properties and to improve the wettability of the fluoropolymer dielectric Cytop. The engineered hydrophilic surface is successfully incorporated in bottom-gate solution-deposited organic field-effect transistors (OFETs) and hybrid organic–inorganic trihalide perovskite field-effect transistors (HTP-FETs) fabricated on flexible substrates. Our analysis of the density of trapping states at the semiconductor–dielectric interface suggests that the increase in the trap density as a result of the chemical treatment is minimal. As a result, the devices exhibit good charge carrier mobilities, near-zero threshold voltages, and low electrical hysteresis

Co‐Evaporated Perovskite Light‐Emitting Transistor Operating at Room Temperature

Solution-processed hybrid organic–inorganic perovskite light-emitting transistors (PeLETs) suffer from low brightness and environmental instability induced by temperature-activated trapping, ionic motion, and polarization effects, which so far have been hindering the realization of devices operating at room temperature. Here high quality thermally co-evaporated methylammonium lead iodide perovskite films are employed to minimize ionic motion and significantly improve the electroluminescence characteristics of the perovskite active layer, enabling stable device operation up to ≈ 310 K. The demonstration of PeLETs operating at and beyond room-temperature paves the way for practical applications in the rapidly evolving area of solid-state lighting, active-matrix displays, and visible light communications.</p