Modulation of Microstructure and Charge Transport in Polymer Monolayer Transistors by Solution Aging

Abstract

Main observation and conclusion A few monolayers of organic semiconductors adjacent to the dielectric layer are of vital importance in organic field‐effect transistors due to their dominant role in charge transport. In this report, the 2‐nm‐thick polymer monolayers based on poly(3‐hexylthiophene) with different molecular weights (Mn) were fabricated using dip‐coating technique. During the monolayer (solid state) formation from the solution, a disorder‐to‐order transition of polymer conformation is observed through UV‐vis absorption measurement. Meanwhile, high Mn polymer monolayer generates higher crystalline fibrillar microstructure than the low Mn one due to the stronger π–π intermolecular packing between polymers. More importantly, the solution aging procedure is utilized to further improve the morphology of polymer monolayers. It is obvious that after aging for 6 d, both fiber dimension and density as well as conjugation length are significantly increased under the same processing conditions in comparison to the fresh solution, and consequently the field‐effect mobilities are remarkably enhanced by 2—4 times. Note that the maximum mobility of 0.027 cm2·V–1·s–1 is among the highest reported values for poly(3‐hexylthiophene) monolayer transistors. These results demonstrate a simple but powerful strategy for boosting the device performance of polymer monolayer transistors.

Prominent processing techniques to manipulate semiconducting polymer microstructures

“…12f). 448 Instead, 6 days aged solutions of both P3HT systems generated, under the same processing conditions, microstructures with increased fiber dimension and density (Fig. 12g and h) that favored longer conjugation lengths, which, in turn, significantly enhanced the OFET charge mobilities.…”

“…Very recently, Lin and co-workers employed solution aging to modulate the microstructure of low and high molecular weight P3HT with the goal to manipulate and enhance the OFET charge transport. 448 A fresh solution of low molecular weight P3HT exhibited weaker π–π interchain packing as compared to its high molecular weight analogue and therefore, displayed lower crystalline fibrillar microstructures (compare Fig. 12e with Fig.…”

“…12g and h) that favored longer conjugation lengths, which, in turn, significantly enhanced the OFET charge mobilities. 448…”

Tuning the nanostructure and molecular orientation of high molecular weight diketopyrrolopyrrole-based polymers for high-performance field-effect transistors

“…In recent years, conjugated semiconducting polymers have attracted extensive attention in both academia and industry because of their intrinsic features, including mechanical flexibility, solution processability, low cost, light weight and high-throughput manufacturing. [1][2][3][4] Importantly, their optoelectronic properties can be efficiently tuned by the rational design of chemical structures, offering great potential in applications like field-effect transistors, light-emitting diodes and photovoltaic devices. [5][6][7][8][9][10] Most conjugated polymers are weakly crystalline due to multiple influencing factors, such as the entanglement of polymer chains 11 and steric hindrance.…”

Crystallization of Poly(ethylene oxide)-Based Triblock Copolymers in Films Swollen-Rich in Solvent Vapors

“…There is a broad range of prominent processing methods that can efficiently alter the microstructure of various polymer chains and tune their molecular arrangements at micrometer and nanometer scales [10,14,[28][29][30][31][32][33][34]. Such methods can be used to align polymer molecules in thin films during [35][36][37] or after [15,33,[38][39][40][41][42][43] their fabrication, as well as in solutions [44][45][46] and in the solid state [14,47,48], and may include the selection of solvent quality [49] and polymer concentration [50], addition of non-solvents [51], employement of convective forces [31,34], thermal annealing [40], pressure [52] or mechanical stretching [53], and use of space confinements [54,55] or annealing in solvent vapors [39,41]. The aforementioned methods mainly rely on physical processes such as self-assembly [56][57][58] or crystallization [40,41,[59]…”