Efficiency enhancement of perovskite solar cells by using Ag- or Ag-Cu composite-doped surface passivation of the electron transport layer

One of the important factors that limit the efficiency of perovskite solar cells (PSCs) involves mobility and charge separation process in perovskite and electron transport layer (ETL). In this study, we showed that a simple introduction of a passivation layer at the surface of ETL helped increase the optical absorption, electron mobility, charge separation, and conductivity of ETL. The passivation layer was prepared by doping the titanium dioxide nanotube with Ag, Cu, or Ag-Cu composite via photo-deposition method. PSC with Ag-and Ag-Cu (60:40)-doped passivation layer showed average conversion efficiency of 11.68% and 10.58%, respectively; the control device showed 8.68% in efficiency under high relative humidity of 50-52%. Such enhancement in performance was largely contributed by the increase in current density (J(sc)) of about 35% and 14% relative to the control device for the passivation layer doped with Ag and Ag-Cu (60:40) composite, respectively. The increase in the current density can be attributed to a decreased recombination caused by better charge mobility and quenching of the improved ETL, as well as better optical absorption of perovskite. The developed passivation layer demonstrates a simple, yet powerful method to enhance solar cell performance, having good potential for various perovskite recipes and structures.