Water-suspended MoO3 nanoparticles prepared by LASIS and fast processing as thin film by ultrasonic spray deposition

Crystalline molybdenum oxide nanoparticles (MoO3 NPs) were prepared by laser ablation synthesis in solution (LASiS). The resulting MoO3 NPs are water suspended with average size of 23 nm. Subsequently, in order to produce hole injection layers for solar cells, these nanoparticles were processed as thin films onto indium tin oxide (ITO)/glass substrate using ultrasonic spray deposition, which allows fast and uniform deposition in large areas with controllable thickness and low roughness; the water is removed by heating the substrate during the processing. Moreover, scanning electronic microscopy images pointed out that the bottom of the films is mainly composed of small nanoparticles. Thereafter, the optimized glass/ITO/MoO(3)NPs/PTB7:PC71BM/Ca/Al solar cells displayed open circuit voltage (V-oc) of 0.75 V, short circuit current density (J(sc)) of 13 mA/cm(2), fill factor (FF) of 58% and power conversion efficiency of 5.7% under AM1.5 illumination, presenting increased stability when compared with devices having polymeric hole transporting layer. Since LASiS method does not require the use of organic precursors/solvents, it is a green route to produce MoO3 NPs. In addition, the ultrasonic spray deposition is a versatile method to achieve homogeneous and transparent thin films from water suspended nanoparticles. The organic solar cell response pointed out the potential use of these procedures to produce hole injection layers for photovoltaic devices.