An inorganic/organic hybrid composite of CuS nanoparticles (NPs) and poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) was prepared via a facile mixing process. Counter electrodes (CEs) of quantum dot sensitized solar cells (QDSSCs) were prepared by coating the hybrid CuS-PEDOT:PSS composite on fluoride-doped tin oxide (FTO) substrates using simple drop-casting technique. The SEM micrographs of CuS-PEDOT:PSS CEs revealed three-dimensional surface morphology and homogeneous dispersion of CuS NPs on the PEDOT:PSS. The electrochemical measurements of the hybrid CEs showed high electrocatalytic activity towards polysulfide electrolyte resulted from embedding the catalytic active CuS NPs into the continuous PEDOT:PSS conducting matrix. The CdS-QDSSC fabricated with CuS- PEDOT:PSS CE exhibited an remarkable stable power conversion efficiency (PCE) of 1 …