Vertical‐Resolved Composition and Aggregation Gradient of Conjugated‐Polymer@Insulator‐Matrix for Transistors and Memory

Abstract

Conjugated polymers are of interest for next‐generation electronics due to their improved flexibility, low cost, and solution processability. However, a conjugated polymer is not a chemically “pure” material because the polymer chains are polydispersed in terms of molecular weights and/or chemical stereoregularities, leading to dispersions of both localized order and electronic properties. Taking advantage of these properties, a one‐step self‐refinement method is proposed to induce film‐depth‐resolved composition and aggregation gradient of conjugated‐polymer@insulator‐matrix for high‐performance organic field‐effect transistors and nonvolatile memories. During solvent evaporation, the higher ordered sub‐components of conjugated polymers are substantially enriched at the top surface of the blend film to form a morphologically continuous sublayer serving as high‐quality transport pathways to warrant high‐performance transistors. The less ordered sub‐components are distributed within insulator‐matrix in the bottom part of the film without connection with each other, which guarantees a reliable composite electret to help store sufficient immobilized charges to tune the operation of the device. Moreover, these conjugated‐polymer@insulator‐matrix films with insulator content as high as 95% show excellent optical transparency (>90%) and environmental stability (for months), which demonstrates great potential for use in transparent electronics.

Reconfigurable Multifunctional Ambipolar Polymer Transistors with Improved Switching-off Capability Upon Non-Uniformly Distributed Compensation Potential

“…decayed at a similar rate and the ratio of them (A836/A195) slightly changed with the increase of etching time, except for the top and bottom interface, demonstrating that no obvious vertical phase separations of conjugated-polymers and insulators occurred in the blend film 55 . In addition, GIWAXS, as a well-established protocol for characterizing the crystalline structure of polymers, was used to characterize the nanostructure change of the conjugate-polymer films 56,57 .…”

“…The absorbance at 195 (A195) and 836 nm (A836) was mainly contributed by the absorption PS and PDPP-4FTVT respectively, which was extracted to reveal the distribution of the two components in the vertical direction of the blend film 55 . As shown in Fig.…”

“…6, introducing uniformly trapped charges only shifted the transfer curves to positive or negative voltages, and the current on/off ratios were almost unchanged. The transfer curve shifts were originated from the trapped charges in the insulatormatrix, which modulated the accumulation and depletion of mobile charges by the electrostatic interaction 14,55 . Stressing the transistor with positive gate voltages could inject electrons into the insulator-matrix and the trapped electrons will enhance the accumulation of holes while suppress the accumulation of electrons, which shifted the transfer curves to positive voltages.…”

“…However, for unipolar transistors, usually only one type of charges could be injected into and trapped in electret, so that the transfer curves can only be unidirectionally shifted, and cannot return to the original state even as the opposite voltage is applied 55,65,66 . In ambipolar transistors, both holes and electrons could be reversibly trapped and released, which is favorable for reversibly switch the device states for realizing flash-type memories 10 .…”

Polymer electrets and their applications

“…SiO 2 , Si 3 N 4 , and muscovite are inorganic electrets, which have the advantage of compatible with microelectronic processing technology and high surface charge density; but they process weak mechanical property 34,35 . In contrast, polymer chains could be featuring different microscopic crystallinities/aggregations to tune the properties besides the light weight and flexibility; therefore, polymer electrets have drawn great attention in both military and civilian applications, including xerography, microphone, transducers, memory devices, energy harvesters, biomedicine, and so on 36–40 …”