Flexible Photodetectors Based on All-Solution-Processed Cu Electrodes and InSe Nanoflakes with High Stabilities

Flexible electronics attract extensive interest in academic research and commercial markets. Fabrication of electronics on flexible substrates remains a great challenge though. Mostly, components of electronics including metal electrodes and functional materials are created via physical vapor deposition (PVD) in conjunction with photolithography. Nevertheless, ultrathin polymeric substrates are susceptible to environmental shocks during PVD. In this paper, a full-solution process for fabricating copper (Cu) electrodes of micrometer (µm) scale on polymeric substrates is realized under ambient conditions via photolithography-patterning polymer-assisted metal deposition (pp-PAMD). Apart from low fabrication costs from instruments capitals and energy inputs, these flexible Cu electrodes show superior mechanical durability. As a proof-of-concept application, large-quantity and high-quality indium selenide (InSe) nanoflakes, obtained by liquid electrochemical intercalation and ultrasonic exfoliation, are deposited on top of flexible Cu electrodes to construct all-solution-processed flexible photodetectors. The as-fabricated flexible InSe photodetectors demonstrate excellent operational stability during 5000 continuous laser on-off cycles, shelf stability under ambient storage conditions without encapsulation for 20 weeks, thermal viability from 90 to 360 K, and flexible stability upon mechanical bending at a radius (r) of 2 mm for 5000 cycles. This work implies the potential of pp-PAMD technique and prospects of solution processes in fabricating flexible electronics.