Boosting Ag ₂ S Solar Cell Efficiency by Back Interface Engineering

ABSTRACT Silver sulfide (Ag 2 S) is an excellent photovoltaic material due to its optimal elemental composition and strong chemical and device stability. A critical factor limiting the further efficiency enhancement of Ag 2 S solar cells lies in the severe carrier recombination losses at the Ag 2 S/ITO back interface, primarily attributed to poor electrical contact and energy barrier mismatch between the absorption layer and ITO electrode. Herein, we propose a novel back‐interface optimization strategy by introducing a Zn‐doped SnO 2 (SnO 2 :Zn) electron transport layer (ETL) at the rear contact of Ag 2 S. The SnO 2 :Zn ETL demonstrates dual‐functionality in Ag 2 S devices: reducing interfacial energy barriers and inducing a transition in the preferred crystalline orientation of the absorption layer from (012) to Furthermore, the formed Zn Sn acceptor defect and V O vacancy defects within SnO 2 :Zn synergistically decrease electron concentration, raise the work function, and thus establish a favorable back‐surface field. These coordinated mechanisms collectively improve charge carrier extraction and suppress non‐radiative carrier recombination. Consequently, the power conversion efficiency of SnO 2 :Zn incorporated Ag 2 S devices is elevated from 1.91% to 2.76%. This innovative strategy provides novel insights into interface engineering for Ag 2 S thin‐film solar cells.