We measured the trend of IV characteristic values under the
illumination of the sun which is 100 mW/cm2 from IV curves both
in dark and light. In Fig. 13, among all, the film of 5 ml GO concentration
having the band gap of 2.71 eV shows the highest Isc
value in lowest Voc. It means it has better photon response in visible
spectrum and best electron transportation in the device. And the
film of 3.75 ml GO concentration shows the lowest performance
because of the presence of defects and impurities.