Barrier layer design reduces top electrode ion migration in perovskite solar cells

Abstract

We report on an examination of mobile ion concentration ( N 0 ) in perovskite solar cells (PSCs) as a function of temperature and device architecture. We report on an examination of mobile ion concentration ( N 0 ) in perovskite solar cells (PSCs) as a function of temperature and device architecture. We find that lower initial N 0 is correlated to devices with higher thermal performance through in situ measurements up to 450 K. Changes in N 0 are observed upon thermal aging and are impacted by the changes made at the electron collecting interface. We examine the extent to which various top electrode materials (Ag, Au, carbon) impact N 0 as well as the effects of tin oxide (SnO 2 ) or an ozone-nucleated SnO 2 (O 3 –SnO 2 ) barrier layer between the ETL and top electrode. Upon thermal aging, we confirm the involvement of Ag ion diffusion through the ETL dependent on the device details. We are able to quantify the degree to which Ag ions migrate or are blocked from migrating into the underlying device layers in the PSC stack. X-ray scattering shows improved suppression of the degradation products formed in the bulk of the perovskite when a blocking layer, particularly the O 3 –SnO 2 is employed.