Thiocyanate ligands as crucial elements for regeneration and photo-degradation in TiO2|dye|CuI solar cells

Size control of CuI grains and thus better-matched interfaces were observed in the presence of crystal growth inhibitors in the CuI coating solution for TiO2|dye|CuI solar cells. Evidence is given that these growth inhibitor molecules simultaneously act as an electron transfer mediator between the CuI and dye molecules via thiocyanate bridges. A reverse reaction of injected electrons from TiO2 nanoparticles electrochemically inactivates the thiocyanate electron transfer bridge in the illuminated cells causing photo-degradation.