Gadolinium-incorporated CsPbI2Br for boosting efficiency and long-term stability of all-inorganic perovskite solar cells

All-inorganic CsPbI2Br perovskite solar cells (PSCs) have received extensive research interests recently. Nevertheless, their low efficiency and poor long-term stability are still obstacles for further commercial application. Herein, we demonstrate that high efficiency and exceptional long-term stability are realized by incorporating gadolinium(III) chloride (GdCl3) into the CsPbI2Br perovskite film. The incorporation of GdCl3 enhances the Goldschmidt tolerance factor of CsPbI2Br perovskite, yielding a dense perovskite film with small grains, thus the α-phase CsPbI2Br is remarkably stabilized. Additionally, it is found that the GdCl3-incorporated perovskite film achieves suppressed charge recombination and appropriate energy level alignment compared with the pristine CsPbI2Br film. The noticeable increment in efficiency from 14.01% (control PSC) to 16.24% is achieved for GdCl3-incorporated PSC. Moreover, the nonencapsulated GdCl3-incorporated PSC exhibits excellent environmental and thermal stability, remaining over 91% or 90% of the original efficiency after 1200 h aging at 40% relative humidity or 480 h heating at 85 °C in nitrogen glove box respectively. The encapsulated GdCl3-incorporated PSC presents an improved operational stability with over 88% of initial efficiency under maximum power point (MPP) tracking at 45 °C for 1000 h. This work presents an effective ion-incorporation approach for boosting efficiency and long-term stability of all-inorganic PSCs.