There are also differences in trends between the 2 models. In the low light intensity region, Model 1 exhibits a negative slope, and Model 2 has a positive slope. This feature is the result of differences in the competition between hole trapping, surface diffusion and accumulation in these models. In Model estimated from the reported incident photon flux) as a signal that hole traps are saturated in the TiO2 crystal. In the present simulations, at this incident power density the overall photocurrents in both models are just starting to transition from their low light intensity to their higher light intensity trends (Figure (b), 1~10 h + nm -2 s -1 ).