Correlation of charge transport with structural order in highly ordered melt‐crystallized poly(3‐hexylthiophene) thin films

Abstract

A series of well-defined poly(3-hexylthiophene)s (P3HT) of different molecular weight (MW) and high regioregularity was investigated for charge transport properties in ascast and melt-crystallized films. The semicrystalline structure of the P3HT was characterized by X-ray scattering and Atomic force microscopy. Crystallization by cooling from the melt led to a substantial increase in crystallinity and a stronger alignment of the crystals in comparison to as-cast films. The increase in crystallinity went along with an increase in hole mobility of up to an order of magnitude as measured by the space charge limited current method. Additionally, the hole mobility depended on the long period of P3HT lamellae and consequently on the MW. In compliance with the long period, the charge carrier mobility first increased with the MW before decreasing again at the onset of chain folding. V C 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2013, 51, 943-951

Tuning crystalline ordering by annealing and additives to study its effect on exciton diffusion in a polyalkylthiophene copolymer

“…3 represent spatial variations in the elastic modulus of the material. 23,26 Stiffer crystalline regions are brighter whilst soft amorphous regions are dark. The image of as spin-coated film from neat solution shows smaller crystalline regions (Fig.…”

“…23,24 Out of these, appropriate annealing is a simple and useful method which enables the arrangement of polymer chains to change in a controllable fashion. 7,22,25,26 There is a report of thermal annealing improving exciton diffusion in semi-crystalline conjugated polymers, 7 however, other studies reported a decrease or no change. 10,27 As semiconducting conjugated polymers consist of long chains, there are several other factors such as entanglement, lamellar orientation, and interchain interactions, that could govern the molecular level ordering or crystallinity.…”

π‐Conjugated Donor Polymers: Structure Formation and Morphology in Solution, Bulk and Photovoltaic Blends

“…[73,74] Moreover, the influence of molecular weight on charge carrier mobility was also elucidated and correlated with the structural features of P3HT lamallae and the tendency for P3HT to fold after reaching a critical molecular weight. [75][76][77] This has also been reviewed for P3HT and different types of conjugated polymers by Stinglein et al and others. [78,79] Moreover, attempts to obtain single crystals of P3HT and to correlate the structural features with optical absorption have been made by Reiter et al [80] These single crystal samples were obtained via crystallization in solution by a self-seeding technique leading to fully-extended chains aligned perpendicular to the substrate.…”

Generalized Kinetic Monte Carlo Framework for Organic Electronics

“…Vanlaeke et al showed that crystallization of P3HT increases the mobility [54]. Sirringhaus et al have demonstrated that the mobility strongly depends on the orientation of the micro-crystalline domains in semi-crystalline P3HT [55,56]. In situ grazing incidence X-ray scattering techniques can be exploited to gain information on the polymer crystallization and ordering [57].…”

“…While for some devices such as OLEDs, a low mobility is critical to optimize the performance, OSCs and OTFTs demand a high mobility. In semiconducting polymers, charge carrier mobility strongly depends on the morphology [54,55], but its interplay is not well understood [52,96]. Investigating the impact of different transport mechanisms, such as intrachain hopping, on carrier mobility can help the development of organic materials and improve device performance.…”