The power conversion efficiency (filled circles) and the zero-bias dark conductance (open triangles) of one sample as a function of time. We note the clear correlation between the decrease in conductance and the increase in efficiency. Denoted on the figure are the symbol that represents the initial efficiency (η_init), the extrapolated point on the y-axis that represents the t = 0 efficiency (η(0)) and the line representing the asymptotic conductance value after long times (G_dark(∞)); these values are explained in the discussion.