Tailoring the Functionality of Additives for Enhancing the Stability of Perovskite Solar Cells

Abstract In a two‐step procedure for fabricating perovskite films, the PbI₂ layer formed on the substrate is converted to perovskite by reacting PbI₂ with organic iodide. Excess PbI₂ left after forming perovskite composition, however, might have an ill effect on device stability and current–voltage hysteresis, although it positively affects efficiency improvement. Additive engineering is reported here on to control the residual PbI₂ in a two‐step procedure. A series of organic multi‐ammonium chloride derivatives are introduced into the PbI₂ precursor solution for the first‐step coating, which results in an increase in the perovskite grain size. In addition, carrier lifetime is elongated due to the reduced trap density and the energetics are adjusted to facilitate the extraction of photogenerated carriers. The aminoguanidinium‐containing precursor leads to an improved power conversion efficiency (PCE) as compared to the bare PbI₂ precursor mainly due to the significantly enhanced open‐circuit voltage and fill factor. Consequently, a PCE of 23.46% is achieved from the hysteresis‐less photovoltaic parameters and 93% of the initial PCE is maintained after aging for 1000 h in ambient conditions.