Dissimilar mechanism of executing hole transfer by WO₃ and MoO₃ nanoparticles in organic solar cells

We investigated the effect of metal oxide nanoparticles (NPs) in poly (3,4 ethylenedioxythiophence):poly (styrene-sulfonate) layer for the light harvestation in poly (3-hexylthiophene):[6,6]-pheny-C₆₁-butyric acid methyl ester organic solar cells. The role of tungsten trioxide nanoparticles (WO₃) and molybdenum trioxide nanoparticles (MoO₃) in enhancing the efficiency of solar cells was compared. Due to the difference in the energy band structure of the two nanoparticles, the WO₃ NPs acted as a hole blocking layer, whereas MoO₃ NPs helped in the hole transfer. The solar cell with WO₃ NPs at 1.5 wt% concentration showed a power conversion efficiency of 4.22% under AM 1.5G illumination and the device blended with 2 wt% of MoO₃ NPs showed a power conversion efficiency of 4.40%. We measured various electrical properties including, electrochemical impedance spectroscopy and recombination mechanisms using the light intensity dependent current-voltage measurement of organic solar cell.