Figure 3.
Result of drift-diffusion simulations of MAPI solar cells showing (a) power conversion efficiency and (b) open-circuit voltage Voc as well as the voltage Vmpp at the maximum power point as a function of the surface recombination velocity S for minority carriers at front and back contact. In addition to S, also the series resistance Rs is varied with higher values of Rs leading to lower efficiencies and voltages Vmpp. The open-circuit voltage stays constant with Rs because there is no current flow in open circuit and therefore no voltage drop over the series resistance. While low values of S guarantee high open-circuit voltages, what counts for efficiency is Vmpp which may be reduced drastically by higher series resistances. This illustrates that contact layers not only have to ensure low S but also low Rs. (Online version in colour.)