Engineering the mesoporous TiO2 layer by a facile method to improve the performance of perovskite solar cells

Highlights: • Crystallization of MAPbI₃ is improved by structural engineering the mesoporous TiO₂. • Unraveling the role of mesoporous TiO₂ structure for PSCs performance enhancement. • Photogenerated charge extraction has been boosted by the O-m-TiO₂. • MAPbI₃-based PSCs achieve a high efficiency of 19.7%. -- Abstract: Inorganic-organic perovskites, such as CH₃NH₃PbX₃ (X = I, Br, Cl), is significant improvements in power conversion efficiencies, demonstrating the enormous potential of perovskite materials. Rapid extraction of photo-generated charge carriers from high-quality perovskite films is essential to achieve efficient perovskite solar cells (PSCs). Here, we devote to improving the charge-extraction ability of the electron transport layers (ETLs) and the crystallization of the perovskite layers by optimizing the ETLs' fabrication process. Insight into the impacts of ETLs architecture on the ETLs/perovskite hetero-interface properties and the quality of perovskite films are originally elucidated. The optimized ETLs increase the open-circuit voltage (V_oc) of the MAPbI₃-based PSCs by up to 100 mV, and the optimal device achieves V_oc ∼ 1.13 V. Under the AM 1.5 simulated sunlight illumination, the optimized PSCs achieves an optimum PCE of 19.7% and maintains good stability after a storage time of 30 days with exposed to the ambient air environment. One of the key limitations of current PSCs performance is effectively solved by this simple optimization method and paves the way for further improve the efficiency through interface engineering.