Managing iodine and tin based defects for efficient and stable mixed Sn-Pb perovskite solar cells

In recent hotly researched tin-lead (Sn-Pb) mix perovskite solar cells (PSCs), the oxidation of Sn2+ is not an isolated process but accompanied by the oxidation of I- to I2, which are both responsible for the severe p-doping and complex defect situation. Diffusion of interstitial I further severely corrodes the metal electrode to fail the PSC. Thereby, managing the I- oxidation and meanwhile neutralizing the movable I- together with suppressing Sn2+ oxidation is quite a challenge for efficient and stable Sn-Pb PSCs. In this work, a natural reductive amino acid (DOPA) is introduced into perovskite layer to successfully inhibit the oxidation of both Sn2+ and I-, at the same time, neutralize the diffusive I- to protect the Ag electrode from corrosion. Benefiting from the improved chemistry situation, the DOPA doped PSC shows significantly promoted photovoltage and efficiency at AM1.5, with enhanced light and shelf stability. This work highlights the importance of I defects management to achieve efficient and stable Sn-Pb PSCs.