Why Inks Made from Polycrystalline Powder are Superior for Low- and Three-Dimensional Perovskite Solar Cells: Role of Size Distribution of Intermediates

Lead-halide perovskite solar cells are conventionally synthesized by mixing precursor salts. However, even slight inaccuracies in weighing can cause stoichiometric errors that limit performance. Perovskite inks derived from crystallized perovskite powder do not suffer from such errors, leading to better solar cells. Powder-processed devices show better JSC (22.36 to 24.21 mA/cm2), FF (77.7 to 79.5%), and PCE (19.27 to 21.47%). The ideality factor reduces from 1.31 to 1.24, and Jo reduces from 3.81 to 0.68 × 10–12 mA/cm2. The powder-processed thin films are also six times more stable at 65 oC and 60% relative humidity. The powder method works well for other perovskite compositions, like low-dimensional perovskites. The efficiency of the (PEAI)2(MA0.9AA0.1)4Pb5I16 solar cell improves from 15.75 to 17.46%, the ideality factor reduces from 1.097 to 1.079, and the Jo reduces from 1.56 to 0.83 × 10–16 mA/cm2. The improvement in device parameters is associated with the recrystallization process, which purifies the solute, reducing the bulk impurities in the perovskite thin film. Additionally, the powder-processed inks have smaller intermediate sizes, lower viscosity, and higher diffusivity, resulting in films having twice the average grain size and a longer carrier recombination lifetime than the salt-processed films. Hence, perovskite inks synthesized from crystallized perovskite powder are superior to those obtained from precursor salts.