The Effect of Tert-butylammonium Addition in Methylammonium Lead Iodide Perovskite Solar Cells

Although methylammonium lead iodide (MAPI) perovskite solar cells have reached efficiencies above 20%, the material is environmentally unstable. Mixing MAPI with lower dimensional (LD) perovskites has been suggested to improve its stability in recent studies. However, the LD-mixed perovskites have lower device performance, likely as a result of limited charge-carrier mobility due to their decreased structural dimensionality. To understand this effect, we mixed large-A-site cation LD perovskites, tert-butylammonium lead iodide, with MAPI, and performed a device performance diagnostics. The results suggested although the charge-carrier lifetime was improved, the mobility decreased by a factor of 20. This contributed to a reduction in device efficiency by 2 orders of magnitude, indicating that mobility plays an important role in 3D/LD perovskite mixtures.