Recently, flexible transparent electrodes (FTEs) have attracted extensive attention as an essential element for future organic electronics (OEs), i.e. solution-processable, scalable and flexible organic electronics (FOEs). Although the traditional transparent electrode indium tin oxide (ITO) has been widely used in OEs, its brittleness and high cost significantly limit its application in the next generation of devices, typically flexible electronics. Thus, many alternatives, such as graphene, carbon nanotubes, conductive polymers, metal nanowires, metal grids and electrospun metallic nanofibers, have arisen at the forefront of FTEs. Among them, silver nanowire (AgNW) networks have attracted particular attention due to their excellent electrical conductivity and high transmittance, as well as facile availability and low cost. Since many studies on AgNWs have been published, a comprehensive review highlighting the advantages of AgNWs in FOEs is highly required. In this review, the synthesis and film fabrication of AgNWs have been firstly summarized, focusing especially on the properties of conductivity and light transmittance. Next, post treatments with different approaches to improve the conductivity of AgNWs have been included. And then, characterization of FTEs has been introduced with details on key parameters for FOEs. Furthermore, AgNW-based FOEs have been summarized to demonstrate the recent progress, such as organic light-emitting diodes (OLEDs), organic solar cells (OSCs), light-emitting electrochemical cells (LECs), organic field effect transistors (OFETs), organic memory devices (OMDs), etc. Finally, perspectives for AgNWs in FOEs have been discussed and concluded as well. It is expected that AgNWs could be the focus of future FOEs compared with other alternatives in terms of their advantages of optoelectronic properties, film-formation, solution-processability and flexibility.

Due to their distinctive two-dimensional (2D) structure and excellent properties, MXenes have got much attention and developed very fast since their discovery in 2011. Generally, 2D MXenes are prepared by selectively etching the A layer from the MAX phases with hazardous fluorine-based acids. Later, more and more moderate routes, such as Lewis acid etching and chemical vapor deposition, have been successfully developed to prepare 2D MXenes without using hazardous etchants. Meanwhile, the intercalation or delamination is also quite important to obtain 2D MXene layers with high quality and high yield. Furthermore, due to the outstanding optoelectronic properties, flexibility, ductility and stability, flexible devices based on 2D MXenes and their nano-composites are quite promising in different fields, such as organic electronics, supercapacitors, metal-ion batteries, electromagnetic interference shielding, sensors, photocatalysis and photothermal therapies, etc. In this review, we firstly summarize the recent development and progress in the preparation of 2D MXenes from chemical and physical routes, as well as the intercalation and delamination techniques including cation intercalation and physical delamination. Furthermore, the applications of 2D MXene in flexible devices have been well discussed from different using routes of MXene including pure MXene, MXene/2D materials, MXene/1D materials and MXene/polymers. Finally, we give a conclusion to this interview and make a perspective on the future directions of 2D MXenes considering the key issues in the MXene community.

PEDOT:PSS/Ti₃C₂T_X composite hole transport layers with fine-tuned nanostructures are facilely fabricated, which shows obviously higher efficiency and stability than that of the control device with pure PEDOT:PSS as HTL.