Synergistic Interface and Band Engineering for Sn-Pb Perovskites

Sn-Pb perovskite solar cells (PSCs) have emerged as potential alternatives to Pb-based counterparts. However, the presence of diverse structural defects, together with suboptimal alignment of the Fermi level (E_F) and bandgap (BG) in the designs of existing Sn-Pb PSCs, severely compromises the integrity of the perovskite layer and hinders the transport of charge carriers, which ultimately results in low power conversion efficiency (PCE) and poor stability. Simultaneous defect passivation and modulation of electronic band structures are highly desirable for improving PCE and stability of Sn-Pb PSC designs. However, achieving this dual optimization remains challenging because an inappropriate passivation approach can adversely affect the electronic band structures of PSC designs. Here, we introduce a multifunctional amphoteric molecular strategy (MAMS), based on a precise combination of phenethyl ammonium thiocyanate (PEASCN) and amino acid HCl (AA HCl), to simultaneously achieve defect passivation and E_F and BG modulation in PSC designs. This strategy delivers enhanced PCE (22.2%), with an open-circuit voltage of 0.86 V and a fill factor of 78.1%, and maintains 80% of initial efficiency over 200 h because of the synergetic effect of PEASCN and AA HCl, which facilitates defect passivation and BG modulation, inspiring the development of MAMS-mediated efficient PSCs.