Solution-Processed SnO _X Layers of an Inverted Wide-Bandgap Perovskite Sub-Cell Enable 28.43%-Efficient All-Perovskite Tandem Photovoltaics

Metal oxide electron transport layers (ETLs) provide compelling advantages relative to organic counterparts for perovskite solar cells (PSCs), including enhanced thermal stability and cost-effectiveness. However, tin oxide (SnO X ) nanoparticles are a promising alternative to traditional fullerene derivatives in inverted PSCs, which still suffer from severe interfacial nonradiative recombination induced open-circuit voltage ( V OC ) loss. Here, we reported the innovative synthesis of SnO X nanoparticles with exceptional dispersibility in 2,2,2-trifluoroethanol and demonstrate their application as efficient ETLs in inverted PSCs with a bandgap of 1.77 eV. By effectively suppressing the nonradiative recombination at the perovskite/SnO X interface, we achieved a record V OC of 1.34 V and a power conversion efficiency (PCE) of 20.15% for inverted PSCs incorporating solution-processed metal-oxide charge transport layers. Furthermore, unencapsulated devices retained over 80% of their initial PCE after 1000 h of thermal stress at 55 °C. Ultimately, this strategy enabled the realization of two-terminal all-perovskite tandem solar cells with a champion PCE of 28.43% (certified 28.34%).