Efficiency and stability improvements for room light dye-sensitized solar cells in the presence of electrochemically fabricated composite counter electrodes

Electrochemical methodologies including constant current, constant potential and cyclic voltammetry (CV), as well as the sputter coating, are utilized to fabricate the poly(3,4-ethylene dioxythiophene) (PEDOT), platinum (Pt), and their composite films with layer-by-layer (Pt/PEDOT) and homogenous (PEDOT-Pt) structures. These films are utilized as counter electrodes of dye-sensitized solar cells (DSSCs). To achieve high cell efficiencies, the thickness of Pt and PEDOT, as well as the structure of composite films are regulated. The results show that PEDOT/Pt and PEDOT-Pt films demonstrate, respectively, the best and worst cell efficiencies. The X-ray diffraction and X-ray photoelectron spectroscopy analysis indicate that PEDOT and Pt have slight interaction in the PEDOT/Pt film, and the Pt preserves a crystalline structure. On the contrary, the interaction of PEDOT and Pt in the PEDOT-Pt film is high, resulting in an amorphous Pt structure. The crystalline Pt and its interaction with PEDOT are considered to be the main reason resulting in the high efficiencies of the corresponding cells. By applying this PEDOT/Pt counter electrode on DSSCs, the charge transfer at the counter electrode/electrolyte interface is significantly increased, and the cells can achieve efficiencies as high as 8.97% and 15.35%, respectively, under one-sun and room-light (200 lux) conditions.