Vibration‐Assisted Crystallization Improves Organic/Dielectric Interface in Organic Thin‐Film Transistors

Crossover from band-like to thermally activated charge transport in organic transistors due to strain-induced traps

“…Our experimental and theoretical results suggest that inhomogeneous strain, which arises from CTE mismatch between the dielectric and organic semiconductor, yields local distortions in the positions of the organic semiconductor molecules that lead to deviations from the molecular equilibrium positions found in the bulk crystal, which in turn induce variations in the charge density distributions and distinct modifications to the band structures at the dielectric-organic semiconductor interface. These effects represent a form of cumulative lattice disorder, which results in the formation of trap states of depth and density correlating with the structural imperfections (55,56). Indeed, we find that, in the temperature range investigated here, the trap density at the interface between the diF-TEG ADT films and SiO 2 dielectric increases by 22% for the LG devices, and by 5 times more for the SG devices, where the difference in thermal behavior is significantly larger.…”

The Influence of Isomer Purity on Trap States and Performance of Organic Thin‐Film Transistors

“…[18, 34–36] We thus employed our vibration-assisted crystallization (VAC) method, in which the semiconductor solution is perturbed with gentle vibrations applied during film growth in a direction perpendicular to the substrate. [12] In an earlier report, we showed that this procedure yields lower trap densities and enhanced device performance by promoting molecular assembly in a lowest-potential energy configuration. In that study, we only accessed the total density of interfacial traps, with no details about their nature or the energetic distribution.…”

“…First, an overall lowering of the trap density can be observed (highlighted as the green checkered area), which results from the fact that a larger fraction of the molecules can reach the configuration corresponding to the global energy minimum instead of local minima, as we have discussed in detail elsewhere. [12] Second, the lack of the signature trap state peak (gray striped area) indicates that only one type of isomer is present at the interface with the dielectric, and thus there is a greater degree of separation between the syn - and anti -isomers compared to the SAC devices.…”

Low-voltage polymer/small-molecule blend organic thin-film transistors and circuits fabricated via spray deposition

“…In addition, note that while mean hole mobilities are lower than in spin-cast devices, the best performing spray-cast OTFTs exhibited a performance on-par with their spin-cast, high operating voltage equivalents and similar to the best hole mobilities reported on diF-TES ADT films. 28 The best performing device that was fabricated from spray-casting exhibited a saturation mobility of $1.8 cm 2 /Vs at À4 V operation. When compared with a mean saturation mobility of $2 cm 2 /Vs at À60 V for the spin-cast devices, this suggests that with further control and automation of the semiconductor deposition, performance on par with the best spin-cast devices can be expected.…”