High Performance Flexible Transparent Electrode via One-Step Multifunctional Treatment for Ag Nanonetwork Composites Semi-Embedded in Low-Temperature-Processed Substrate for Highly Performed Organic Photovoltaics

For ideal flexible transparent electrodes, the features of good electrical/optical properties, low surface roughness, efficient charge transportation, robust electrical stability under simultaneously continuous operation bias, and mechanical bending are critical. Herein, a flexible transparent electrode fulfilling all these features is demonstrated by silver (Ag) nanonetwork composites semi-embedded in low-temperature-processed colorless polyimide (cPI), which shows a figure of merit over 1000 (5.4 omega sq(-1) sheet resistance and >94% diffused transmission at 550 nm wavelength), extremely smooth topography (<1 nm root-mean-square roughness and <3 nm peak-to-valley roughness), remarkable bending stability under continuous operation bias, and increased work function favoring the band alignment with typical charge transport layers for efficient devices. These characteristics are attributed to one-step multifunctional chemical treatment on the composite of Ag nanowires and an example polymer of poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS). The strategic one-step process simultaneously offers selective welding at nanowires cross junctions to form an Ag nanonetwork, and removing polyvinylpyrrolidone surfactant from Ag nanowires and PSS from PEDOT:PSS. The flexible electrode also favors the residue-free cPI transfer for applications. Flexible organic solar cells (OSCs) made from the electrode achieve an averaged power conversion efficiency of 14.46% (best, 15.12%), which is the best flexible OSCs reported so far.