Ambipolar charge-trapping in self-assembled nanostructures of a supramolecular miktoarm star-shaped copolymer with a zinc phthalocyanine core

Abstract

Nonvolatile organic field-effect transistor (OFET) memories have attracted considerable attention owing to their potential applications in flexible and wearable electronic devices. The novel design of a charge-trapping material based on supramolecular miktoarm star copolymers (μ-stars) consisting of star-shaped polystyrene with a zinc phthalocyanine core (ZnPcPS₄) and a pyridyl end-functionalized polymer (py-polymer) has been studied to explore the influence of self-assembled morphology on the final device performances. Supramolecular μ-stars containing the ZnPc core showed distinctive phase-separated nanostructures in the films that were different from typical polymer blends. The OFET memory devices embedded with supramolecular μ-stars exhibited ambipolar charge-trapping behavior with photoresponsive characteristics, resulting in a wide memory window (47 V) with a high on/off current ratio (>10⁷) for a long period of time (>10⁴ s). Furthermore, the charge-trapping properties of the polymer memory layer were studied using Kelvin probe force microscopy (KPFM), revealing enhanced charge-trapping capabilities attributed to nanoscale phase separation in the supramolecular μ-stars. This study provides the design and concept of charge-trapping materials for next-generation high-performance OFET memory devices.