Perovskite-Type BaTiO3 Nanocrystal Modifier in TiO2/CH3NH3PbI3 Interface to Enhance the Performance of Planar Perovskite Solar Cells

Interfacial modification plays a vital role in boosting the performance of planar perovskite solar cells (PSCs). Here, perovskite-type BaTiO 3 nanocrystals prepared by immersing dense blocking TiO 2 (bl-TiO 2 ) in Ba(NO 3 ) 2 solution were used as an interfacial modifier. The interface bonding was improved due to the fact that BaTiO 3 and CH 3 NH 3 PbI 3 (MAPbI 3 ) have the same structure. Incorporation of BaTiO 3 nanocrystals effectively boosted the electron extraction rate and suppressed the carrier recombination at the interface. The MAPbI 3 grains nucleated and grew rapidly, resulting in larger grain size after introduction of BaTiO 3 nanocrystals. Photoluminescence (PL) spectroscopy, time-resolved PL decay spectroscopy, and electrochemical impedance spectroscopy measurements verified that the BaTiO 3 nanocrystals indeed promoted the carrier separation rate while suppressing nonradiative carrier recombination. By optimizing the bl-TiO 2 /MAPbI 3 interface, the power conversion efficiency of planar PSCs based on bl-TiO 2 /BaTiO 3 was improved from 15.03% to 17.71% [ J sc  = 22.49 mA/cm 2 , V oc  = 1.12 V, fill factor (FF) = 70%].