Novel ytterbium-doped CsPbI2Br thin-films–based inorganic perovskite solar cells toward improved phase stability

In this study, we used ytterbium (Yb2+) as a dopant in the CsPbI2Br inorganic perovskite thin film and stabilized its black phase. Here, we varied the Yb2+ doping concentration in the CsPb1−xYbxI2Br (x = 0–0.04) perovskite phase through simple solution method. The optimum concentration of Yb2+ showed improved morphology and crystal growth. The fabricated all-inorganic perovskite solar cells (IPVSCs) having CsPb0.97Yb0.03I2Br-based champion device showed the highest 15.41% power conversion efficiency (PCE) for a small area of 0.09 cm2 and 14.04% PCE for a large area of 1 × 1 cm2 with excellent reproducibility, which is higher than the controlled CsPbI2Br device. Detailed photovoltaic analysis revealed that the PCE, open-circuit voltage (VOC), short circuit current density (JSC) and fill factor (FF) of the final IPVSC device attributed to the suppressed charge recombination, better film quality, and well growth orientation of the perovskite film. Moreover, the champion CsPb0.97Yb0.03I2Br device retains >85% initial efficiency after 280 h under 85 °C thermal annealings. Our results provide a new method to boost the performance of the photovoltaic application.