Influence of doped charge transport layers on efficient perovskite solar cells

Abstract

Metal halide perovskites have emerged as the most promising materials for the next generation of solar cells, achieving record efficiencies over 22%. In most of the reported high efficiency vapor deposited perovskite solar cells the perovskite absorber layer is sandwiched in between charge selective transport layers. The conductivity of these layers is frequently enhanced by “doping” them with additives that lead to an excess of charge concentration. Key advantages of using doped layers classically include reduced series resistance and the formation of ohmic contacts to the external electrodes, both enhancing the fill factor of the cells. The main drawback, however, lies in the stability of the devices, which can be reduced when doped layers are employed. Here, we study the influence of the doped and undoped transport layers on fully evaporated p-i-n devices. We propose a strategy to improve stability and efficiency by removing the doped layers in a series of different layouts. The use of undoped transport layers on the n-side notably enhances the stability. On the other hand, the use of undoped transport layers on the p-side lead to higher current densities. On average 18 % of power conversion efficiency was reached, improving the stability and reliability of fully evaporated perovskite solar cells.