Bionic Levodopa-Modified TiO2 for Preparation of Perovskite Solar Cells with Efficiency over 23%

TiO 2 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 TiO 2 precursor solution for the modification of TiO 2 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 TiO 2 /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 TiO 2 /LDA-Cl can accelerate the charge extraction and inhibit the recombination of electron–hole pairs at the interface between the perovskite and TiO 2 . The nonradiative recombination of the LDA-Cl-based perovskite solar cell is suppressed, and the defect density is reduced from 5.513 × 10 16 to 5.093 × 10 16 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%).