The measured and fitted photocurrent-voltage curves for ITO/TiO
/MEH-PPV/Au devices. (a-c) Panels are for the devices with different TiO2 and MEH-PPV layer thicknesses measured under the same illumination intensity; while (c, d) panels are used to show the influence of illumination intensity on the same device. The incident intensity was 15.85 mW/cm2 (a-c), 3.0 mW/cm2 (d) and 9.6 mW/cm2 (e). The k
0 values obtained by fitting the experimental data to Equation 15 are marked on the respective panels.