Oriented blend films of poly(3-hexylthiophene) and [6,6]-phenyl-C61-butyric acid methyl ester fabricated by friction transfer method

Abstract

We have been studying oriented thin films of polymers fabricated by the friction transfer method, which allows a variety of conjugated polymers to be aligned into highly oriented films. However, with this method it is difficult to prepare oriented films from a mixture. In this work we prepared oriented thin films of a mixture of regioregular poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM), which is a promising combination for application in organic solar cells. We obtained oriented blend films of P3HT and PCBM by the friction transfer method from a solid block prepared from a mixed solution with a weight ratio of 1 : 1. Atomic force microscopy shows that microscale phase separation took place in the blend films. Polarized UV–visible spectra show that the P3HT chains were aligned parallel to the friction direction in the blend films. X-ray diffraction studies suggested that the preferred orientation of P3HT crystallites was the “face-on” orientation in the blend film.

Local structure of semicrystalline P3HT films probed by nanofocused coherent X-rays

“…[4][5][6][7][8][9] Typical features of these polymers are mixtures of poor, disordered and well organized, crystalline domains. [12][13][14][15] Controlling the morphology and orientation of the crystalline domains in polymer films is a crucial step for the fabrication process, since it determines key electronic properties of the material, such as charge carrier mobility and charge separation, and defines the overall device performance. [12][13][14][15] Controlling the morphology and orientation of the crystalline domains in polymer films is a crucial step for the fabrication process, since it determines key electronic properties of the material, such as charge carrier mobility and charge separation, and defines the overall device performance.…”

“…10,11 Commonly, it is assumed that a higher degree of crystallinity substantially improves device efficiency. 9,15,16 The crystalline domain sizes of P3HT can be varied in the range of tens to few hundreds of nanometers, depending on preparation techniques. 9,15,16 The crystalline domain sizes of P3HT can be varied in the range of tens to few hundreds of nanometers, depending on preparation techniques.…”

“…9,15,16 The crystalline domain sizes of P3HT can be varied in the range of tens to few hundreds of nanometers, depending on preparation techniques. 15,19 They are defined by a different orientation of crystalline domains with respect to the substrate. 15,19 They are defined by a different orientation of crystalline domains with respect to the substrate.…”

“…1(a)], and perpendicular in the case of edge-on domains [ Fig. 4,15,20 P3HT films can be prepared using various methods, for example, drop-casting, spin-coating, dip-coating or directional crystallization, leading to a different degree of crystallinity and preferred orientation of P3HT domains. The shortest distance between P3HT layers, called p-p stacking distance, is equal to b/2, where b is a unit cell parameter [ Fig.…”

“…1(b)]. 5,15,21,22 The formation of a particular morphology of the film is defined by macromolecular parameters (molecular weight, regioregularity, polydispersity, etc. 1(a) and (b)].…”