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 ∼600 S cm^-1 down to a film thickness of 0.2 μm, and a high optical transmittance of about 85% at 550 nm. Furthermore, the new casting method significantly reduced the sheet resistance (∼90 ω/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. High-performance flexible polymer electronic devices are demonstrated using electrodes fabricated with a new film-casting method, involving polyaniline doped with camphorsulfonic acid (PANI:CSA). The lowered sheet resistance of the PANI:CSA electrodes resulted in excellent device performance compared with the devices fabricated using a conventional spin-casting method. The flexible polymer light-emitting diodes produced an enhanced brightness of 6000 cd m^-2, and the flexible polymer solar cells exhibited a higher power conversion efficiency of 2%.