Self-stratified semiconductor/dielectric polymer blends: vertical phase separation for facile fabrication of organic transistors

Abstract

Semiconducting/insulating polymer blends are promising materials for use in organic thin film transistor (OTFT) applications. Here, vertically phase-separated poly(3-hexylthiophene) (P3HT)-top and poly(methyl methacrylate) (PMMA)-bottom blend films were developed for the facile fabrication of OTFTs with excellent electrical properties. The microstructures of the blend films could be adjusted simply by altering the film processing conditions, which impacted the electrical properties of the OTFTs based on the blend films. A decrease in the P3HT content of the blend film significantly reduced the interface roughness between the semiconductor (P3HT) and dielectric (PMMA) layers, which reduced charge trapping or scattering, thereby increasing the field-effect mobility. A higher solution concentration tended to increase the drying time during film deposition, which allowed the P3HT molecules to self-organize over a long period of time. This led to an increase in the ordering of the phase-separated P3HT film, which significantly improved the device performance. TFTs based on a P3HT/PMMA (1/39 w/w) film prepared from a 4 wt% blend solution showed the best field-effect performance with a saturated field-effect mobility of 0.022 cm 2 V À1 s À1 and an I on /I off current ratio of 2 Â 10 5 . The vertically stratified P3HT/PMMA films were also suitable for the fabrication of all-polymer TFT devices on flexible substrates.

Thickness-dependent electrical properties of soluble acene–polymer blend semiconductors

“…The increased time resulted in diF-TES-ADT crystals with larger grain size. This is in accordance with the work of Qiu et al, which reports similar concentration effects in P3HT/PMMA blends [9]. When the solution concentration was increased further (30 mg/ml), spherulites with a Maltese cross pattern were observed, as shown in Fig.…”

“…Because charge transport occurs at the dielectric/semiconductor interface laterally, the conducting pathway from the source to drain electrode should be well-defined. Therefore, inducing vertical phase separation is an effective method for obtaining high mobility in OFETs [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21]. For example, it has been demonstrated that a phase-separated structure comprising an insulating polymer top layer and an organic semiconductor bottom layer-poly(methyl methacrylate) (PMM A)-top/poly(3-hexylthiophene) (P3HT)-bottom-increases environmental stability in bottom-gate/bottom-contact OFETs [6].…”

Organic Semiconductor/Insulator Polymer Blends for High-Performance Organic Transistors

“…Low voltage driven OFETs have been successfully fabricated because a phase-separated thin PMMA layer can work as a gate dielectric (Figure 3b). Wang et al, examined the effect of film processing conditions (i.e., solution concentration) on the morphology of the phase-separated interface between P3HT and PMMA [30]. A higher solution concentration tended to decrease roughness of the phase-separated interface.…”

Surface Directed Phase Separation of Semiconductor Ferroelectric Polymer Blends and their Use in Non‐Volatile Memories

“…[23,24] This pioneering work focused on the methodology of this approach rather than incorporating these patterned layers in electronic devices. Morphology control by surface directed phase separation was explored in organic light emitting diodes [ 25 , 26 , 27 ] , photovoltaics [28] and thin film transistors [29,30] . Next, we show that this bottom-up approach also works for ferroelectric-semiconductor blends.…”