Acetamidinium substituted methylammonium lead iodide perovskite solar cells with higher open-circuit voltage and improved intrinsic stability

摘要： We report Acetamidinium (AA) substituted methylammonium lead iodide perovskite solar cells. AA has a restricted C-N bond rotation, due to delocalized 3+ electron cloud over C-N bond and presence of an additional N-H bond (4H-bond in AA as compared to 3H-bond in MA). These bonding structures strengthen the electrostatic interaction and stabilizes the acetamidinium cation inside the perovskite matrix. AA, a larger cation, is substitutional only up to 10%. Devices made with 10% AA-substituted films show average Voc of 1.12 V, higher than the average Voc of 1.04 V in case of MAPbI3. This increase in Voc can be attributed to increase in carrier lifetime from 20 μs in case of MAPbI3 to 32 μs for 10% AA substituted films respectively. Devices with 18.29% champion and 16.3% average efficiency were fabricated for films with 10% AA. Degradation experiments confirm that the material stability also makes devices more stable; under ambient exposure (72–3% RH) devices with 10% AA retain 70% of their initial power conversion efficiencies (PCE) upto 480 h. Under same conditions, the PCE’s of reference MAPbI3 devices reduced to 43% of their initial value in 480h.