Spiro-OMeTAD,　as　a　crucial　component　of　hole-transporting　layer　(HTL),　exhibits　limited　mobility　and　conductivity,　and　the　lithium　bis-trifluoromethanesulfonimide　dopant　is　sensitive　to　water　vapor,　which　imposes　restrictions　on　the　photovoltaic　properties　of　perovskite　solar　cells　(PSCs).　Herein,　the　iron–porphyrin　(FePP)　is　introduced　into　Spiro-OMeTAD　solution　as　additive,　which　facilitates　the　oxidation　process　of　Spiro-OMeTAD,　leading　to　the　enhancement　of　hole　mobility　and　hole　extraction　and　transport.　Besides,　the　surface　Pb2+　defects　of　perovskite　film　are　cured　by　the　presence　of　carboxylic　acids　(-COOH)　in　FePP.　As　a　result,　the　photovoltaic　properties　of　PSCs　with　FePP　additive　have　been　improved　with　a　power　conversion　efficiency　(PCE)　of　21.58%.　Moreover,　FePP　can　further　anchor　Li+　ions　in　HTL　to　prevent　it　from　being　invaded　by　water　vapor.　Dramatically,　the　degradation　of　unencapsulated　devices　with　FePP　is　suppressed　significantly,　which　retains　82.0%　of　its　original　PCE　under　10–20%　relative　humidity　(RH)　after　7100　h　and　maintains　about　79.6%　of　its　original　PCE　under　50–60%　RH　after　1000　h.　Thus,　this　study　shows　that　the　design　and　development　of　multifunctional　HTL　additives　holds　great　potential　for　achieving　highly　efficient　and　durable　PSCs.　©　2024　Wiley-VCH　GmbH.