Bioinspired solar cell design: Organic thiols as rectifying electron transfer bridges in WS2/TiO2 nano solar cells

Nano solar cell materials cannot sustain imprinted thermodynamic potentials yielding electrical fields for a charge separation. They have, therefore, to rely on kinetic mechanisms for current rectification and energy conversion. It is shown that treatment of WS2 nano-sheet sensitized TiO2-material with organic thiols increases the photocurrent efficiency at least three fold. They bind to the WS2 via the thiol sulfur to produce a charged surface state, which converts into an efficient electron transfer bridge in presence of suitable electron donors. These thiol bridges essentially operate in anodic direction. Thus they increase both the photo induced chemical affinity, which is proportional to the photovoltage generated, and the interfacial reaction rate which is proportional to the photocurrent. The results underline the importance of studying unidirectional electron transfer processes for innovative solar cell applications.