Improving the Long-Term Stability of BPQD-Based Memory Device via Modification with Polyvinylpyrrolidone-Grafted Polydopamine

Long-term environmental stability of electronic and optoelectronic devices is a very important concern. Both black phosphorus (BP) nanosheets and quantum dots (BPQDs) exhibit very poor environmental stability. To address this problem, a new encapsulation approach for improving long-term stability of the BPQD-based electronic devices, which concerns two-step in situ polymerizations: 1) in situ polymerization of dopamine in the presence of BPQDs giving a BPQDs@PDA (PDA: polydopamine) composite; 2) in situ atom transfer radical polymerization of N-vinyl-2-pyrrolidone on the BPQDs@PDA surface producing the BPQDs@PDA-PVP composite (PVP: polyvinylpyrrolidone), is developed. Both the Al/BPQDs@PDA-PVP/ITO and Al/BPQDs:PVP blends/ITO devices show excellent nonvolatile memory performance at the initial measurement stage. Interestingly, the former can only be programmed to the high conductivity state in the positive bias range, while the latter can be switched into the ON state only in the negative bias range. The different switching directions may be highly associated with the inherent electronic structural characteristics of the materials. In contrast to the BPQDs:PVP blends and/or BPQDS@PDA:PVP blend-based electronic devices with very unstable memory performance, the memory performance of the BPQDs@PDA-PVP-based device remains unchanged even standing for 90 d.