Novel Film-Casting Method for High-Performance Flexible Polymer Electrodes

A new film-casting method for polymer electrodes is reported, in which thickness-controlled drop-casting (TCDC), using polyaniline doped with camphorsulfonic acid (PANI:CSA) is used. By combining the advantages of conventional spin-casting and drop-casting methods, and by rigorously controlling the film formation parameters, flexible polymer electrodes with high conductivity and excellent transmittance can be produced. The PANI: CSA electrodes cast by the TCDC method exhibited constant thickness-independent conductivities of similar to 600 S cm(-1) down to a film thickness of 0.2 mu m, and a high optical transmittance of about 85% at 550 nm. Furthermore, the new casting method significantly reduced the sheet resistance (similar to 90 Omega/square) of the PANI: CSA electrodes compared with the conventional spin-cast films, enhancing the performance of the devices deposited on plastic substrates. The flexible polymer light-emitting diode produced a brightness of 6000 cd m(-2), and the flexible polymer solar cell exhibited a power conversion efficiency of 2%, both of which were much higher than those of the devices fabricated by the conventional spin-casting method.