All-Perovskite Tandems Enabled by Surface Anchoring of Long-Chain Amphiphilic Ligands
Aidan Maxwell, Hao Chen, Luke Grater, Chongwen Li, Sam Teale, Junke Wang, Lewei Zeng, Zaiwei Wang, So Min Park, Maral Vafaie, Siraj Sidhik, Isaac Metcalf, Yanjiang Liu, Aditya D. Mohite, Bin Chen, Edward H. Sargent
Abstract
Perovskite solar cells (PSCs) in the pin structure are limited by nonradiative recombination at the electron transport layer (ETL) interface, which is exacerbated in narrow-bandgap (∼1.2 eV) Pb–Sn PSCs due to surface Sn oxidation and detrimental p-doping. Photoluminescence quantum yield studies herein indicated that ethane-1,2-diammonium (EDA) passivation only partially alleviates perovskite/ETL energetic losses. We pursued passivation of the defect-rich perovskite:ETL interface to reduce nonradiative losses; our target was to combine chemical coordination of Sn sites with the introduction of an interlayer, which we implemented by introducing long-chain carboxylic acid ligands at the perovskite surface. Treatment with oleic acid (OA) led to reduced recombination at the perovskite/ETL interface and evidence of Sn 2+ coordination. This reduced the V OC deficit of Pb–Sn PSCs to 0.34 V, resulting in a 0.89 V V OC and PCE of 23.0% (22.4% stabilized). Incorporating the OA-treated Pb–Sn layer into a monolithic all-perovskite tandem, we report a 27.3% PCE (26.4% certified) and a V OC of 2.21 V.