Environmentally Friendly Plasma-Treated PEDOT: PSS as Electrodes for ITO-Free Perovskite Solar Cells
27-12-2017 19:04
Solution processed poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) transparent electrodes (TEs) offer great potential as a low cost alternative to expensive indium tin oxide (ITO). However, strong acids are typically used for enhancing the conductivity of PEDOT:PSS TEs, which produces processing complexity and environmental issues. This work presents an environmentally friendly acid free approach to enhance the conductivity of PEDOT:PSS using a light oxygen plasma treatment in addition to solvent blend additives and post treatments. The plasma treatment was found to significantly reduce the sheet resistance of PEDOT:PSS TEs from 85 to as low as 15 Ω sq-1, which translates to the highest reported conductivity of 5012 S/cm for PEDOT:PSS TE. The plasma treated PEDOT:PSS transparent electrode resulted in an ITO-free perovskite solar cell efficiency of 10.5%, which is the highest reported efficiency for ITO-free perovskite solar cells with a PEDOT:PSS electrode that excludes the use of acid treatments. This is the first demonstration of this technology. Moreover, the PEDOT:PSS TEs enabled better charge extraction from the perovskite solar cells and reduced the hysteresis in the current density-voltage (J-V) curves.