Asymmetric Organic Diammonium Salt Buried in SnO2 Layer Enables Fast Carrier Transfer and Interfacial Defects Passivation for Efficient Perovskite Solar Cells

For perovskite solar cells (PSCs), the presence of interfacial defects limits device's efficiency and long-term stability. Reasonably passivating the interfacial defects and reducing the non-radiative recombination concerning perovskite layer are effective ways to achieve high-efficiency PSCs. Herein, we report an effective method by using an asymmetric diammonium salt of N, N-dimethyl-1,3-propanediamine dihydroiodide (DMA-PAI(2)) buried in SnO2 layer to modify the interface between electron transport layer (ETL) and perovskite (PVK) layer. The burying of DMAPAI(2) into SnO2 not only improves the electron mobility of SnO2 ETL, but also optimizes the energy level arrangement of ETL/PVK interface. In addition, the crystallinity of PVK is enhanced and the defects at the buried interface are passivated. Based on this strategy, the power conversion efficiency (PCE) of PSCs is significantly improved from 20.78% to 23.20%. Meanwhile, as compared to the control device, the DMAPAI(2) modified PSCs exhibited better operational stability under 1-sun illumination at maximum power point, and retained over 85% of its initial PCE after 1200 h continuous irradiation. These results indicate that burying suitable ammonium salt in ETL is an effective interfacial modification strategy to boost the device's PCE and stability.