Functionalized SnO2 films by using EDTA-2 M for high efficiency perovskite solar cells with efficiency over 23%

The electron transport layer (ETL) is of great importance for preparing high-efficiency perovskite solar cells (PSCs). Here we introduced EDTA-2 M (M represents K, Rb or Cs) molecules to stabilize SnO2 colloids, and improve the electrical and surface properties of the SnO2 films. With the help of EDTA-2 M, the electron mobility of SnO2-based perovskite films is increased from 3.6 × 10-4 to 1.27 × 10-3 cm2V-1s−1. In addition, EDTA-2 M molecules can effectively passivate the interface defects of SnO2 and promote the quality of the perovskite films. All the improvements suppress the carrier recombination, leading to a smaller open circuit voltage (VOC) loss. Finally, the 1.57 eV bandgap PSCs based on EDTA-2 M modified SnO2 realized a champion efficiency of 23.30% (VOC = 1.171 V) with a negligible hysteresis, while the 1.69 eV bandgap perovskite device reached an efficiency of 19.76% (VOC = 1.266 V). The unencapsulated PSCs based on EDTA-2 M modified SnO2 only drop 5% of the initial efficiency after being exposed to the ambient atmosphere for 1200 h.