Efficiency Enhancement in P3HT:PCB Blends using Squarylium III Dye"

Abstract

Nano-size thin films comprising poly (3-hexylthiophene) (P3HTi and 3 fullerene derivative [6, 6] PhenylC,-butyric acid methyl ester (PCBl"l) incorporating squaryliurn dyes III (sq3) are reported. The materials prepared were evaluated for their optical, e le ctrical and phOIO'(\'I1\ er51011 efficiency. i\bterials comp: ising a blend ratio I :0.6: I of P3HT:SQ3:PCBM \\ ere de pos itcd b~ <pin-coating or screen printing to produce thin films measuring 100 11m and subsequently annealed at l-l(l'(' [or ] 0 min. The films were characterized by UV-Vis-NIR spectroscopy for their optic al prope n ie s. .uomic force microscopy fur surface morphology and film thickness, and electrical properties Optical measurements for blends incorporating different amounts of dye showed increased photo-absorbance with increasing dye concentration. The combined contribution of squarylium ]]1 dye and thermal annealing resulted in increased power conversion efficiency (11) or pristine P3HT:PCBl\1 solar cells from 2.8 % to 3.9 ~(' The dye in the active layer improved photo-absorption by enhanced light han'esting while thermal treatment improved the nanoscale morphology leading to better metal-film interface contact and broadening of the absorpt ion wave length range.