Impact of Li passivation on recombination and charge transfer at the TiO2/perovskite interface

This research aims to comprehensively examine the dynamics of charge transfer occurring at the interface of Li-doped titanium dioxide (TiO2) and perovskite. The specific focus is on investigating the mitigation of intrinsic defects at the interface between the electron transport layer (ETL) and perovskite, aiming to understand and address trap-assisted recombination. Compared to the pristine control cell, the Li-doped TiO2-based perovskite solar cell (PSC) showed a notable improvement in conversion efficiency, increasing from 17.6 to 20.2%. Additionally, the open circuit voltage (V-oc) value increased from 1090 to 1120 mV, accompanied by a decrease in current density-voltage (J-V) hysteresis upon doping. The introduction of Li-doping led to a notable enhancement in recombination resistance, signifying a reduced recombination rate and improved charge transfer at the interface. These observations were evident in electrochemical impedance spectroscopy (EIS) measurements conducted both in the absence and in the presence of light. Furthermore, various charge transfer kinetics, such as charge transfer resistance, recombination lifetime, and diffusion length, were calculated to fully clarify the effect of Li passivation. EIS analysis demonstrated that the TiO2:Li-based solar cell displayed increased recombination resistance, suggesting enhanced charge carrier dynamics at the TiO2/perovskite interface compared to the bare TiO2. Additionally, the reduction in trap-assisted recombination, as indicated by improved chemical capacitance, recombination lifetime, and diffusion length values upon Li passivation, underscores the effectiveness of this approach in optimizing solar cell performance. The research delved into the impact of Li passivation on the TiO2/perovskite interface and the performance of PSCs by examining structural, optical, morphological, and electronic aspects.