Freezing‐Solidification‐Vacuum Drying Strategy for Preparing High‐Quality 2D BP and COFs‐Based Bilayer Heterojunction

Abstract All the known methods (e.g., mechanical exfoliation, liquid‐phase exfoliation, ionic shearing, chemical vapor deposition, nano‐precipitation, etc.) cannot be used to prepare uniformly distributed black phosphorus (BP) nanolayers on a large scale, while the vapor deposition method brings a huge cost burden (e.g., material costs, equipment and energy consumption, process efficiency and yield, scalability, and throughput). This unevenly distributed BP layer will cause significant performance differences among the same batch of memristors due to the differences in the film layers when preparing memristors, which will greatly limit its application in memristors and optoelectronic devices. To address this problem, a freezing‐solidification‐vacuum drying (FSVD) strategy has been successfully developed to prepare high‐quality 2D BP films on a large scale. This approach is also used to transfer the EB‐COF film prepared using the liquid‐liquid interface assisted method to the BP film coated onto the ITO substrate. The as‐fabricated bilayer heterojunction device, Al/EB‐COF/BP/ITO, exhibits an excellent memristive performance at a small sweep voltage range of ±1V. By utilizing this outstanding performance, a convolutional neural network is constructed to achieve the encryption and recognition of image data.