Screening organic passivation layers for triple-cation triple-halide perovskite solar cells enabling high efficiencies with negligible hysteresis

Abstract We systematically compare various organic materials, namely ethylenediammonium diiodide (EDAI 2 ), n-octylammonium iodide (OAI), phenylethylammonium iodide (PEAI), formamidinium iodide (FAI), and guanidinium bromide (GABr), as passivation of the perovskite/electron transport layer (pk/ETL) interface. We use an inverted cell process based on triple-cation triple-halide perovskites ( E g = 1.57 eV) fabricated by wet-chemical spin-coating. The ETL is deposited by vacuum evaporation of C 60 and BCP. We reach efficiencies up to 21.2% for ‘unpassivated’ cells, limited by recombination losses at the pk/ETL interface. EDAI 2 is found to provide the highest efficiencies of up to 25.2% with negligible hysteresis of the J-V -characteristics due to its excellent interface passivation in combination with a low contact barrier, leading to a combination of high open-circuit voltage of 1184 mV and high fill factor of 83.3%. GABr still provides efficiencies up to 23.3%, however, the fill factor is significantly lower compared to the EDAI 2 -passivated interface, possibly due to the formation of a contact barrier. All other examined materials show, despite high open-circuit voltages up to 1204 mV for OAI, worse overall cell performances. EDAI 2 is hence identified as the most effective material for pk/ETL interface passivation amongst the examined materials. The stability of EDAI 2 -passivated cell is found to be 90% of the initial efficiency remaining after 2700 h dark storage.