Efficient photon-to-electron conversion with rhodamine 6G-sensitized nanocrystalline n-ZnO thin film electrodes in acetonitrile solution

This work encompasses a study of the photosensitizing action of the commercially available laser dye rhodamine 6G (Rh 6G) on nanocrystalline n-ZnO thin film electrodes prepared by sol–gel technique. This dye, having strong absorption in the visible range with a pronounced absorption peak at 525 nm, was found to convert into electrical energy the visible light in the range of 450–560 nm. The electron injection by photo-excited dye molecules into the conduction band of ZnO was evidenced by the matching of the action spectrum of dye-capped ZnO electrode with the absorption spectrum of the dye in solution. The maximum incident photon-to-current conversion efficiency (IPCE) of Rh 6G-sensitized ZnO based cell was found to be 2.3% at 520 nm under short-circuit condition, which is nearly 1.5 times the IPCE value reported for Rh 6G-sensitized SnO2 based cell. Dependence of the photocurrent on light intensity and the stability of the photocurrent obtainable from the Rh 6G-sensitized ZnO based photoelectrochemical cell on its prolong operation were also determined. On irradiation of the semiconductor electrode with monochromatic light (λ=520 nm), the power conversion efficiency (η) of the (ZnO electrode/ Rh 6G—containing electrolyte/carbon electrode) cell was found to be 0.2% with fill factor value of 0.44. Open-circuit photovoltage up to ∼500 mV could be obtained with this cell under visible (λ>420 nm) and white lights illumination.