Efficient and luminescent perovskite solar cells using defect-suppressed SnO2 via excess ligand strategy

The deposition of electron-transport layers using chemical bath deposition (CBD) enables high efficiency in perovskite solar cells. However, the conventional CBD methods require time to achieve uniform films on large substrates and often fail to deposit high-quality films due to incomplete surface coverage and oxidation. Here we show an excess ligand strategy based on the CBD of tin oxide (SnO2), suppressing the cluster-by-cluster pathway while facilitating the ion-by-ion pathway to create uniform films. Our approach enables rapid synthesis of high-quality SnO2 electron-transport layers with reduced defect densities. The resulting SnO2 thin films exhibit superior optoelectronic properties, including a low surface-recombination velocity (5.5 cm s−1) and a high electroluminescence efficiency of 24.8%. These improvements result in a high power-conversion efficiency of 26.4% for perovskite solar cells, an efficiency of 23% for perovskite modules and an efficiency of 23.1% for carbon-based perovskite cells. This highlights its potential for the low-cost, large-scale production of efficient solar devices.