Controllable Multistep Preparation Method for High‐Efficiency Perovskite Solar Cells with Low Annealing Temperature in Glove Box

Abstract

Perovskite solar cells (PeSCs) fabricated by a two‐step method have achieved high power conversion efficiency (PCE). Although two‐step fabrication makes the formation of perovskite films much easier to control, the too fast reaction between the lead source (such as PbI2) and halogenated organic/inorganic cation (such as formamidinium iodide [FAI]) during the high‐temperature (≈150 °C for FAPbI3) annealing hinders further reaction progress, leaving a large amount of unreacted lead source. This annealing in air is a mandatory step to achieve high‐quality perovskite films and then high‐efficiency devices with the aid of moisture, which is detrimental to device stability. Herein, a multistep preparation procedure (recoating FA0.9MA0.1I solution) is proposed to obtain a well‐defined perovskite film with large crystal domain size (≈ several micrometers) and reduced grain boundary at low annealing temperature without the help of moisture (i.e., 60 °C in glove box). As a result, a device with high PCE up to 19.301% is achieved using the multistep prepared perovskite film. The high‐quality perovskite film is attributed to the dissolution–recrystallization process during the repeated FA0.9MA0.1I coating procedure. The capability of this multistep method is further demonstrated in fabricating high‐performance devices (PCE of 17.762%) without the annealing procedure.