Efficient and Stable All-Lead Perovskite Tandem Solar Cells Enabled by All-Inorganic CsPbI2Br Top Cells

Fabricating all-perovskite tandem solar cells (APTSCs) is promising to overcome the thermodynamic limit of single-junction perovskite solar cells. Here, we demonstrate efficient and stable APTSCs based on Pb-based perovskites - a 1.91 eV cesium lead iodide bromide (CsPbI2Br) and a 1.51 eV formamidinium cesium lead triiodide (FA0.95Cs0.05PbI3). We introduce poly[3-(4-methylamine carboxybutyl)thiophene] (P3CT-N) to modify NiOx hole transport layer (HTL) for the wide-bandgap CsPbI2Br cells. The HTL surface modification enhances charge extraction and suppresses the formation of the detrimental interfacial layer, leading to high performance and stability of wide-bandgap CsPbI2Br solar cells. These advances allow us to demonstrate efficient and stable all-Pb APTSCs consisting of CsPbI2Br/FA0.95Cs0.05PbI3 subcells with power conversion efficiencies (PCEs) exceeding 22% and an operational lifetime of more than 1,000 hours under one sun illumination at similar to 65 (A) over cap degrees C.