Enhancing Charge Transport and Stability in Perovskite Solar Cells Through Kbt-Modified Titanium Dioxide Electron Transport Layers

This study investigates the impact of Potassium Bitartrate (KBT) modification on the TiO₂ Electron Transport Layers (ETLs) in planar Perovskite Solar Cells (PSCs). The KBTtreated TiO₂ ETLs exhibit improved energy level alignment, enhanced wettability, and a reduction in interfacial defects, as demonstrated by FTIR, XPS, and UPS analyses. The functional groups (SO₃⁻ and CF₃⁻) in KBT interact with defect sites in both the TiO₂ and perovskite films, thereby improving charge transfer efficiency and inhibiting trap-assisted recombination. Additionally, KBT treatment enhances the morphological properties of the perovskite film, increasing grain size and reducing surface roughness, which in turn improves crystallinity and reduces defects. These structural and interfacial improvements contribute to a notable enhancement in the performance of the PSCs, achieving a Power Conversion Efficiency (PCE) of 25.22%, reduced hysteresis, and improved stability under light and environmental stress. The enhanced wettability of the KBT-treated TiO₂ ETL was concluded based on FTIR, XPS, and UPS results. FTIR analysis revealed the presence of KBT’s functional groups (SO₃⁻ and CF₃⁻) on the TiO₂ surface, which increased its surface polarity and hydrophilicity. XPS further confirmed changes in the chemical composition and bonding configuration of TiO₂, indicating improved surface interactions. Additionally, UPS showed a shift in the energy levels of the TiO₂ surface after KBT treatment, suggesting better energy level alignment with the perovskite layer. These combined results indicate that KBT modification enhances the wettability of the TiO₂ ETL, leading to better perovskite layer deposition and improved charge transfer. This study demonstrates that KBT modification offers a promising, scalable solution to address the key challenges in PSCs, enhancing their performance and long-term stability, and providing valuable insights for future advancements in photovoltaic technology.