Tensile properties of two-dimensional poly(3-hexyl thiophene) thin films as a function of thickness

Abstract

Ultra-thin conjugated polymer films are promising candidates for flexible electronics, but the effect of the film thickness on the tensile properties of 2D conjugated polymer films at the several-nanometer scale...

A Simple Method to Tailor the Electrical and Tensile Properties of Poly(3-hexylthiophene) Ultrathin Films

“…The thicknesses of the P3HT5 films are all below 10 nm, indicating that these films are ultrathin films. Currently, the most commonly used method to tailor the electrical and mechanical performance of CP ultrathin films is the modulation of the thickness of ultrathin films by changing the solution concentration or spin-coating speed. ,– A thickness of a few nanometers significantly changes the tensile properties, such as the modulus and glass transition temperature, which directly affect the tensile properties, of CP ultrathin films. However, reports related to improvement of both the electrical properties and stretchability by modulating the microstructures of CP ultrathin films instead of varying the film thickness are rare.…”

“…To verify the accuracy of the AFM measurements, we obtained an UV–vis absorbance-film thickness calibration curve and found that the thickness of the P3HT5-90-80 film spin-coated at 3600 rpm is 2.1 nm, as shown in Figure S10, in accordance with that measured by AFM. The thicknesses of monolayer P3HT films obtained by spin-coating, , vertical phase separation, – and Langmuir–Schäfer (LS) methods were reported to be 1.6 nm, 1.9, and 2.5 nm, respectively. The different thicknesses of the P3HT monolayer films are attributed to changes in the molecular stacking and hexyl chain folding.…”

“…Two-dimensional (2D) CP films are usually defined as ultrathin films with a thickness of several monolayers, namely, less than 10 nm. , 2D ultrathin films simplify the complex multiscale structure of CPs and offer an ideal platform for studying the structure–property relationships of thin films. The mechanical and optical properties of ultrathin films are beneficial for flexible and transparent devices, and CP ultrathin films have received attention in recent years. – CP ultrathin films can be prepared by solution methods, such as spin-coating, , the Langmuir–Schafer method, bar coating, dip coating, or vertical phase separation. – The solutions for fabricating CP ultrathin films are commonly dilute solutions with concentrations far below the critical semidilute solution concentration ( c *). Due to the lack of contact between molecular chains, improving the crystallization and microstructure of CPs is difficult except by adding a bad solvent into the dilute solution or decreasing the solution temperature to form CP nanowires. – However, CP nanowires are brittle, which limits the application of CPs in flexible devices.…”

“…They modulated the microstructure evolution and electrical properties of P3HT ultrathin films by varying the ultrathin thickness. Qiu’s group prepared P3HT ultrathin films with good order by vertically phase separating P3HT and poly­(methyl methacrylate) (PMMA) blends and then etching PMMA. – To form a vertically phase-separated structure, the ratio of the semiconducting polymer to the insulating polymer should be carefully controlled at a small value to avoid lateral or dual phase separation. This group stripped and transferred P3HT films onto substrates, and repeated the process several times to obtain P3HT ultrathin films with various thicknesses.…”

Optimizing Spin-Coat Speed for Fabrication of P3HT: PCBM Solar Cells

“…The possibility of developing flexible electronic devices and displays using conjugated polymers has drawn the attention of researches working worldwide [1][2][3][4][5][6][7][8][9][10][11]. This is due to the fact that conjugated polymers possess a wonderful combination of semiconductor-like optical and electrical properties along with mechanical strength similar to that of plastic [12][13][14][15][16]. The most important advantage of polymers over inorganic semiconductors is that they can be doped either as p-or n-type using simple oxidation or reduction reactions, respectively [17,18].…”