Electrohydrodynamic spinning of random-textured silver webs for electrodes embedded in flexible organic solar cells

• Published in: Journal of the Korean Physical Society 2017, 70(6), , pp.598-605
• Main Authors: Yoon, Dai Geon, Chin, Byung Doo, Bail, Robert
• Format: Article
• Language: English
• Subjects: Electrical junctions; Electrodes; Electrohydrodynamics; Electrospinning; Energy conversion efficiency; Free form; Glass substrates; Heterojunctions; Indium tin oxides; Mathematical and Computational Physics; Nanowires; Nozzles; Optoelectronic devices; Particle and Nuclear Physics; Photopolymerization; Photovoltaic cells; Physics; Physics and Astronomy; Polymer matrix composites; Process parameters; Short circuit currents; Silver; Solar cells; Theoretical; Topology; 물리학
• ISSN: 0374-4884; 1976-8524
• DOI: 10.3938/jkps.70.598

A convenient process for fabricating a transparent conducting electrode on a flexible substrate is essential for numerous low-cost optoelectronic devices, including organic solar cells (OSCs), touch sensors, and free-form lighting applications. Solution-processed metal-nanowire arrays are attractive due to their low sheet resistance and optical clarity. However, the limited conductance at wire junctions and the rough surface topology still need improvement. Here, we present a facile process of electrohydrodynamic spinning using a silver (Ag) - polymer composite paste with high viscosity. Unlike the metal-nanofiber web formed by conventional electrospinning, a relatively thick, but still invisible-to-naked eye, Ag-web random pattern was formed on a glass substrate. The process parameters such as the nozzle diameter, voltage, flow rate, standoff height, and nozzle-scanning speed, were systematically engineered. The formed random texture Ag webs were embedded in a flexible substrate by in-situ photo-polymerization, release from the glass substrate, and post-annealing. OSCs with a donor-acceptor polymeric heterojunction photoactive layer were prepared on the Ag-web-embedded flexible films with various Ag-web densities. The short-circuit current and the power conversion efficiency of an OSC with a Ag-web-embedded electrode were not as high as those of the control sample with an indium-tin-oxide electrode. However, the Ag-web textures embedded in the OSC served well as electrodes when bent (6-mm radius), showing a power conversion efficiency of 2.06% (2.72% for the flat OSC), and the electrical stability of the Ag-web-textured patterns was maintained for up to 1,000 cycles of bending.