Polystyrene-sulfonate-doped polypyrrole: Low-cost hole transport material for developing highly efficient organic solar cells

The hole transport layer (HTL) is a vital part in an organic photovoltaic (OPV) device for improving hole extraction ability. The HTL of OPV devices is typically prepared using poly (3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS). However, it presents several disadvantages, including causing deterioration of the active layers, exhibiting sensitivity to ultraviolet radiation, and possessing a short lifespan. Hence, focus has increased on alternative p-type semiconductors with improved environmental stability, easier processing, and higher conductivity. In this study, we prepare water-stable, low-cost, and low-acidity PSS-doped polypyrrole (PPY) with varying PSS concentrations for use as the HTL in OPV devices. The films formed using PPY:PSS exhibit an extremely high transmittance within the visible range. The PPY:PSS HTL-based OPV may reach to highest power conversion efficiency of 5.0% (ie, 11% higher than a PEDOT:PSS-based one) when using an optimal PSS concentration in PPY.