The effect of p/n junction position on perovskite solar cell efficiency by changing polarity of the perovskite layer

Abstract

Four types of perovskite solar cells (PVK PV) were fabricated to investigate the effect of charge separation interface (p/n junction) for inverted and normal structures. For inverted structures, (1) TCO/p-type/p-PVK/n-type and (2) TCO/p-type/n-PVK/n-type, were prepared by changing the PVK composition. For normal structures, (3) TCO/n-type/n-PVK/p-type and (4) TCO/n-type/p-PVK/p-type structures were fabricated in the same way. The solar cell efficiency of (2) was better than that of (1), and (3) showed a higher efficiency than (4). In all cases, the cell in which the p/n junction is located at the back side of the PVK layer from the incident light direction gave higher efficiency. Band bending, Fermi level, and carrier mobility were measured for these PVK layers and solar cells. We concluded that the higher efficiency for (2) and (3), where both cells of the p/n junction are located on the bottom of the PVK layer, is explained by the higher mobility of minority carriers, respectively.