The effects of Organic Solvents and their Co-solvents on the Optical, Structural, Morphological of P3HT:PCBM Organic Solar Cells

摘要

The effect of different solvents on the optical, structural, morphology and solar cell performance of P3HT:PCBM based devices were carried out using UV-visible absorption spectroscopy, XRD, AFM, SEM, electrical conductivity as well as current density-voltage (J-V) measurements in dark and under illumination. Chloroform (CF), chlorobenzene (CB), dichlorobenzene (DCB), and their mixtures (DCB:CB, DCB:CF and CF:CB) in the ratio 1:1 were used as solvents to produce active layers of P3HT:PCBM heterojunctions. UV-visible absorption spectra have demonstrated different absorption intensities subject to the used solvents as well as a decrease in the optical bandgap from around 1.9eV to 1.8eV. AFM and SEM images gave an indication on the films' morphological properties, which have exhibited different topographies due to the used solvent. The electrical conductivity as well as the dark J-V characteristics were analysed using Richardson-Schottky model as well as space charge limited conduction theory to evaluate the diode properties of the produced solar cells. The electrical conductivity were found to vary from 9.7-77.7 mS.cm~(-1) and the higher values were associated with using CB:CF co-solvents based devices while the series resistance decreased from 33.3KΩ to 0.54KΩ using the same co-solvents. This was associated with an increase in the charge carriers' mobility that reached 6.69×10~(-6) cm~2V~(-1)s~(-1) in CB:CF based device. OSC devices produced using CB:CF co-solvents has exhibited the highest performance with PCE=2.73%, FF=53% and J_(sc)=8.3mA.cm~(-2) while V_(oc) remained unchanged.