High-performance perovskite solar cell based on mesoporous TiO2 electron transport layer enabled by composite treatment strategy

Mesoporous TiO 2 (m-TiO 2 ) is widely used in the preparation of perovskite solar cells (PSCs) due to its fast carrier transfer and strong light scattering capacity, but the trap states of TiO 2 will cause serious recombination, which will affect the performance of the PSCs to a great extent. Surface treatment is an efficient way to passivate the surface defects of TiO 2 and improve the performance of devices. In this study, we introduce a TiO 2 composite treatment strategy that treats TiO 2 films with low-concentration hydrochloric (HCl) solution and ultraviolet ozone (UVO). The composite treatment has no adverse impact on the structure of TiO 2 , which can be confirmed by X-ray diffraction (XRD), atomic force microscope (AFM), and scanning electron microscope (SEM) measurement. X-ray photoelectron spectroscopy (XPS) shows a 4.62% decrease of surface oxygen vacancies in TiO 2 films, which means the composite treatment can reduce the surface defects resulting from oxygen vacancies. To further explore the carrier transfer performance of treated TiO 2 films, the time-resolved photoluminescence (TRPL) spectroscopy and space charge-limited currents (SCLC) measurement were used. The measurements show a decrease to 59.03 ns of average charge carrier lifetime and a 0.023 V reduction of limit voltage, indicating a stronger electron extraction capability and less defect states. Finally, we achieve a power conversion efficiency (PCE) of 18.9% compared to 17.6% for the control PSCs.