Organic n‐Type Molecule Mediated Crystallization Regulation for Sn‐Pb Perovskite Solar Cells

ABSTRACT

Narrow‐bandgap Sn‐Pb perovskites have showcased great potential for constructing tandem perovskite solar cells (PSCs). However, Sn ^{2 +} in Sn‐Pb PSCs is readily oxidized to Sn ^{4 +} , and such B‐site Sn ^{4 +} will introduce excess positive charge and causes severe p‐type self‐doping, which pins the Fermi level and aggravates non‐radiative recombination. Additionally, the Sn‐based component crystallizes far more rapidly than that of Pb, resulting in unbalanced Sn‐Pb crystallization. To address these challenges, we develop a novel n‐type molecule NDBH as perovskite additive. This molecule offers three key advantages: prevents the oxidation of Sn ^{2 +} through chelation and blocks oxygen ingress along grain boundaries; balances the crystallization rates of Sn‐Pb perovskite by selectively chelating Sn ^{2 +} ; modifies the perovskite surface to be more n‐type. With this organic n‐type molecule, the inverted Sn‐Pb PSCs achieve power conversion efficiency (PCE) of 24.11%. The devices also exhibited remarkable long‐term stability, retaining over 90% of their initial efficiency after 600 h of maximum power point (MPP) tracking. This approach of designing multifunctional n‐type molecules offers a new perspective for enhancing the efficiency and stability of Sn‐Pb PSCs.