WO₃ Nanoparticles or Nanorods Incorporating Cs₂CO₃/PCBM Buffer Bilayer as Carriers Transporting Materials for Perovskite Solar Cells

In this work, we demonstrate a novel carrier transporting combination made of tungsten trioxide (WO₃) nanomaterials and Cs₂CO₃/PCBM buffer bilayer for the fabrication of perovskite solar cells (PSCs). Two different types of WO₃, including nanoparticles and nanorods, were prepared by sol-gel process and hydrothermal method, respectively. Cs₂CO₃/PCBM buffer bilayer was inserted between WO₃ and perovskite layers to improve charge transfer efficiency and formation of pinhole-free perovskite layer. Besides, the leakage current of the devices containing Cs₂CO₃/PCBM buffer bilayer was significantly suppressed. The optimized device based on WO₃ nanoparticles and Cs₂CO₃/PCBM bilayer showed an open-circuit voltage of 0.84 V, a short-circuit current density of 20.40 mA/cm², a fill factor of 0.61, and a power conversion efficiency of 10.49 %, which were significantly higher than those of PSCs without Cs₂CO₃/PCBM buffer bilayer. The results revealed that the combination of WO₃ nanomaterials and Cs₂CO₃/PCBM bilayer provides an effective solution for improving performances of PSCs.