Alkyl‐Chain‐Length‐Independent Hole Mobility via Morphological Control with Poly(3‐alkylthiophene) Nanofibers

Abstract

The field‐effect transistor (FET) and diode characteristics of poly(3‐alkylthiophene) (P3AT) nanofiber layers deposited from nanofiber dispersions are presented and compared with those of layers deposited from molecularly dissolved polymer solutions in chlorobenzene. The P3AT n‐alkyl‐side‐chain length was varied from 4 to 9 carbon atoms. The hole mobilities are correlated with the interface and bulk morphology of the layers as determined by UV–vis spectroscopy, transmission electron microscopy (TEM) with selected area electron diffraction (SAED), atomic force microscopy (AFM), and polarized carbon K‐edge near edge X‐ray absorption fine structure (NEXAFS) spectroscopy. The latter technique reveals the average polymer orientation in the accumulation region of the FET at the interface with the SiO2 gate dielectric. The previously observed alkyl‐chain‐length‐dependence of the FET mobility in P3AT films results from differences in molecular ordering and orientation at the dielectric/semiconductor interface, and it is concluded that side‐chain length does not determine the intrinsic mobility of P3ATs, but rather the alkyl chain length of P3ATs influences FET diode mobility only through changes in interfacial bulk ordering in solution processed films.

High‐Performance FETs Prepared From Electrospun Aligned P4TDPP Nanofibers

“…[ 1 ] The FET mobility of organic active layer could be manipulated by chemical structures and morphology, such as crystallinity, grain size, molecular packing, and orientation. [ 2 ] Several processing approaches have been employed to enhance the mobility of conjugated polymers, including electrospinning, [ 3 ] solution shearing, [ 4 ] zone casting, [ 5 ] and pretreatment of precursor solution such as crystallineinduced procedure. [ 6 ] We are particularly interested in conjugated-polymer electrospun (ES) nanofi bers because they have the advantages of low cost, fl exible morphology tuning, and high-throughput continuous production.…”

Structure and Morphology Control in Thin Films of Conjugated Polymers for an Improved Charge Transport

“…The longer and/or branched alkyl side-chains and larger alkyl side-chain density could cause an increase of the inter-ring torsion and lead to a relatively more coil-like and flexible conformation, which could tune aggregation and transport properties in turn (Figure 13a). Firstly, Oosterbaan et al proposed that the morphology at FET active interface could be tuned by side-chain length for P3ATs [124]. The solubility of P3AT with a shorter side-chain was larger and it started to aggregate at early stage during casting, resulting in a longer time for crystallites growth.…”

Structure and morphology control in thin films of regioregular poly(3‐hexylthiophene)

“…49 However, several groups have demonstrated the possibility to produce crystalline nanofibrils or whiskers of P3HT from solution in a controlled manner with a high yield. [62][63][64][65][66] Starting from a hot solution of P3HT in a ''marginal'' solvent such as xylene, slow cooling triggers aggregation and crystallization of nanofibrils as evidenced by a characteristic 610 nm peak in the absorption spectra. 64 By successive cycles of centrifugation and crystallization, it was possible to isolate the M w fractions prone to crystallize and obtain pure suspensions of crystalline P3HT fibrils that were used for the elaboration of organic solar cells (see Fig.…”