Scalable Solution-Processed Hybrid Electron Transport Layers for Efficient All-Perovskite Tandem Solar Modules.

All-perovskite tandem solar cells offer the potential to surpass the Shockley-Queisser (SQ) limit efficiency of single-junction solar cells while maintaining the advantages of low-cost and high-productivity solution processing. However, scalable solution processing of electron transport layer (ETL) in p-i-n structured perovskite solar subcells remains challenging due to the rough perovskite film surface and energy level mismatch between ETL and perovskites. Here, we develop scalable solution processing of hybrid fullerenes (HF) with blade-coating on both wide-bandgap (∼1.80 eV) and narrow-bandgap (∼1.25 eV) perovskite films in all-perovskite tandem solar modules. The HF, comprising a mixture of fullerene (C 60 ), phenyl C 61 butyric acid methyl ester and indene-C 60 bisadduct, exhibits improved conductivity, superior energy level alignment with both wide-bandgap and narrow-bandgap perovskites, and reduced interfacial non-radiative recombination when compared to the conventional thermal-evaporated C 60 . With scalable solution-processed HF as the ETLs, the all-perovskite tandem solar modules achieved a champion power conversion efficiency of 23.3% (aperture area = 20.25 cm 2 ). Our study paves the way to all-solution processing of low-cost and high-efficiency all-perovskite tandem solar modules in the future. This article is protected by copyright. All rights reserved.