On the Role of Interfaces in Planar‐Structured HC(NH 2 ) 2 PbI 3 Perovskite Solar Cells

Planar‐structured HC(NH 2 ) 2 PbI 3 (FAPbI 3 ) perovskite solar cells were prepared via a two‐step deposition process. To investigate the role of interface, the perovskite morphology was intentionally modified by varying HC(NH 2 ) 2 I concentration. Surface and grain sizes of the deposited FAPbI 3 became rougher and larger as the HC(NH 2 ) 2 I concentration decreased from 58.2 to 40.7 m M . Average photocurrent was improved but photovoltage deteriorated slightly with decreasing concentration. Consequently, the average efficiency was improved from 7.82 % to 10.70 % and the best efficiency of 12.17 % was obtained at 40.7 m M . Photoluminescence (PL) at TiO 2 /FAPbI 3 interface was reduced with decreasing concentration, which was, however, reversed at FAPbI 3 /spiro‐MeOTAD one. By correlating PL data and the photovoltaic performance, we concluded that the TiO 2 /perovskite interface plays a crucial role in determining photocurrent while the perovskite/spiro‐MeOTAD interface is important in governing photovoltage.