Bionic Levodopa-Modified TiO₂for Preparation of Perovskite Solar Cells with Efficiency over 23%

TiO2 is one of the most common electron transport layer materials, but its poor conductivity, charge extraction, and photostability pose great challenges to the efficiency and stability of perovskite solar cells. Herein, a levodopa molecule was chlorinated to form LDA-Cl in a TiO2 precursor solution for the modification of TiO2 via the phenolic hydroxyl group of levodopa. Uncoordinated lead ions and halogen vacancies of a perovskite can be passivated by carboxyl and chloride ions of LDA-Cl. The as-prepared TiO2/LDA-Cl film exhibits higher conductivity and flatness after annealing and could be well suited for the preparation of large-grain perovskites. The appropriate energy level position and excellent electrical conductivity of the as-obtained TiO2/LDA-Cl can accelerate the charge extraction and inhibit the recombination of electron-hole pairs at the interface between the perovskite and TiO2. The nonradiative recombination of the LDA-Cl-based perovskite solar cell is suppressed, and the defect density is reduced from 5.513 × 1016 to 5.093 × 1016 cm-3 due to the passivation effect of carboxyl and chlorine of LDA-Cl. The photoelectric conversion efficiency of the as-prepared perovskite solar cell increased to 23.28 from 21.91%, and the PCE of the device remained at 90% of the initial value after 4000 h (T = 25 °C, RH = 25%).