Enhancing halide ion homogeneity in blade-coated wide-bandgap perovskite for perovskite-organic tandem solar cells

The shared processing technologies of perovskite and organic semiconductors make them ideal partners for constructing perovskite-organic tandem solar cells. However, the different crystallization rates of bromide and iodide ions lead to inhomogeneous vertical halide distribution within wide-bandgap (WBG) perovskite films, causing notable open-circuit voltage ( V OC ) loss. In this study, we developed an approach to blade-coat halide-compositionally homogeneous WBG perovskite films by introducing a hydrogen-bonding donor solvent (formamide). The formamide effectively modulates crystallization kinetics via balancing the differential hydrogen-bonding interactions of formamide with bromide and iodide ions. The resultant WBG perovskite solar cells achieved a power conversion efficiency of 18.9% with an exceptional V OC of 1.41 volts. Last, a perovskite-organic tandem solar cell was fabricated, achieving a high efficiency of 26.3% (certified as 25.6%) and retaining 92% of its initial efficiency after being illuminated for 1000 hours. This work provides an approach for the large-area fabrication of halide-compositionally homogeneous WBG perovskite films, paving the way for the industrialization of tandem devices.