Sodium Oleate-Modified Tin Oxide Electron Transport Layer for High-Performance Perovskite Solar Cells

Internal and surface defects in the tin oxide (SnO2) electron transport layer (ETL) affect the performance of perovskite solar cells (PSCs). Herein, an effective strategy is designed to modify these defects for high-performance PSCs by incorporating sodium oleate (NaOA) into the SnO2 ETL. The as-prepared SnO2 + NaOA layer provides multiple nucleation sites to assist in the growth of the perovskite film with high crystal quality, increasing the charge transport capacity and suppressing nonradiative recombination. A champion power conversion efficiency (PCE) of up to 17.62% is obtained for PSCs with SnO2 + NaOA ETL, corresponding to a filling factor (FF) of 76.00%, an open-circuit voltage (V OC) of 1.104 V, and a short-circuit current density (J SC) of 21.00 mA/cm2. Besides, this device maintains an initial PCE of 86.17% in nitrogen for 30 days, compared with only 82.02% for the control device. Finally, it is found that the enhancement of J SC can be attributed to the long-chain alkyl groups, and -COO- and Na+ play a key role in boosting V OC and FF. This work provides a promising strategy to optimize ETLs using amphiphilic surfactants for high-performance devices.