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

Large open-circuit voltage ( V 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 V oc loss. The PerSCs include a [Cs 0.22 FA 0.78 Pb(I 0.85 Br 0.15 ) 3 ] 0.97 (MAPbCl 3 ) 0.03 (1.67 eV) absorber and deliver an efficiency of 21.47% and a V oc of 1.21 V ( V oc loss of 0.46 V). More importantly, the unencapsulated PerSCs maintain 90% of the initial efficiency after aging 500 h in N 2 . A buried interface treatment by hexachlorotriphosphazene is developed to suppress the open-circuit voltage ( V oc ) loss in wide bandgap perovskite solar cells (PerSCs). The PerSCs include a 1.67 eV absorber and deliver a high efficiency of 21.47%.