Sn Perovskite Solar Cells with Tin Oxide Nanoparticle Layer as Hole Transport Layer

Tin perovskite solar cells (Sn–PVK-PVs) are a promising alternative to lead perovskite solar cells (Pb–PVK-PVs). Poly (3,4-ethylenedioxythiophene) polystyrene sulphonic acid (PEDOT:PSS) is employed as the hole transport layer (HTL). However, the matter of concern is the damage of the Sn-PVK layer by the acidic properties of the PEDOT:PSS. Therefore, PEDOT:PSS-free Sn–PVK-PV is eagerly awaited. In this paper, the inorganic hole collectors using commercially available SnO 2 nanoparticles (Nano SnO 2 ) are reported. It is well-known that Nano SnO 2 works as an electron transport layer for Pb–PVK-PVs. However, we found that the Nano SnO 2 surface was reduced to SnO x ( x < 2) nanoparticles (abbreviated as P-Nano SnO x ) when the Nano SnO 2 contacted with the Sn-PVK layer, and the resulting P-Nano SnO x works effectively as the HTL of the Sn–PVK-PVs. The efficiency of 9.77% is reported. Furthermore, P-Nano SnO x devices showed higher stability in comparison to PEDOT:PSS devices.