Hexachlorotriphosphazene-assisted buried interface passivation for stable and efficient wide-bandgap perovskite solar cells

Abstract

Large open-circuit voltage (<i>V</i>_oc) loss is the main issue limiting the efficiency improvement in wide bandgap perovskite solar cells (PerSCs). Herein, a facile buried interface treatment by hexachlorotriphosphazene is developed to suppress the <i>V</i>_oc loss. The PerSCs include a [Cs_0.22FA_0.78Pb(I_0.85Br_0.15)₃]_0.97(MAPbCl₃)_0.03 (1.67 eV) absorber and deliver an efficiency of 21.47% and a <i>V</i>_oc of 1.21 V (<i>V</i>_oc loss of 0.46 V). More importantly, the unencapsulated PerSCs maintain 90% of the initial efficiency after aging 500 h in N₂.