Efficient Energy Harvesting in SnO2?Based Dye-Sensitized Solar CellsUtilizing Nano-Amassed Mesoporous Zinc Oxide HollowMicrospheres as Synergy Boosters

摘要

Finding the material characteristics satisfying most of thephotovoltaic conditions is difficult. In contrast, utilization of foreign materialsthat can contribute to light harvesting and charge transfers in the devices is nowdesirable/thought-provoking. Herein, a binary hybrid photoanode utilizingnano-amassed micron-sized mesoporous zinc oxide hollow spheres (meso-ZnOHS) in conjunction with SnO2 nanoparticles (NPs), i.e., SnO2 NP_ZnO HS(for an optimized weight ratio (8:2)), displayed a nearly ～4-fold increase in theefficiency (η) compared to that of bare SnO2 nanoparticle device. Enhanceddevice efficacy in the composite photoanode-based device can be accredited tothe dual function of nano-amassed meso-ZnO HS. Nano-amassed micron-sizedZnO HS embedded in the photoanode can increase the light-harnessingcapability without sacrificing the surface area as well as optical confinement oflight by multiple reflections within its cavity and enhanced light-scatteringeffects. Electrochemical impedance spectroscopy analysis revealed an extendedlifetime of electron (τe) and a higher value of Rct2 at the working electrode/dye/redox mediator interface, indicating a minimumphotoinduced electron interception. The open-circuit voltage decay reveals a slower recombination kinetics of photogeneratedelectrons, supporting our claim that the nano-ammased meso-ZnO HS can serve as an energy barrier to the photoinjectedelectrons to retard the back-transfer to the electrolyte. Moreover, the improvement in the fill factors of the composite-baseddevices is endorsed to the facile penetration of the electrolyte through the pores of nano-amassed meso-ZnO HS, whichincreases the regeneration probability of oxidized dyes.