Abstract
In perovskite solar cells (PSC), the fluorine-doped tin oxide (FTO) glass and hole transport material (HTM) form ohmic contacts, which lead to recombination of charge carriers and consequently reducing the cell performance seriously. The recombination is effectively reduced via introducing a blocking layer (BL) between FTO glass and titanium dioxide (TiO2) mesoporous layer, which eliminates the contact between FTO and HTM, and results in suppressing the recombination between electrons in FTO and holes in HTM. Therefore, preventing the recombination from direct contact between FTO and HTM layer is crucial for high efficiency PSC. In this study, an ultra-thin and compact TiO2 BL on FTO glass was prepared by galvanostatic anodic deposition. This electrodeposition (ED) method can control the morphologies and thicknesses of TiO2 film by manipulating the current density and coulomb density. The material properties of BLs preparimg by various deposition conditions and their photoelectrochemical performances were also scrutinized. Ultraviolet -Visible Spectrometer (UV-Vis) spectra show that the transmittance of FTO substrate is not affected by the ED-BL. FESEM (Field emission scanning electron microscope) images reveal that the structure of the TiO2 film is affected by the depositing current density. As the current density increases, the particle size became smaller. Evidenced by TOF-SIMS (Time-of-flight secondary ion mass spectrometer) and CV (Cyclic voltammogram), it is proved that the interfacial recombination is profoundly suppressed by ED-BL. Comparing to the commonly used spin coating (SC) method to deposit BL, our study shows that the high quality BL can effectively enhance the performance of perovskite solar cell especially at short circuit current density JSC (mA/cm2) and fill factor FF via decreasing the electrons loss from FTO glass to HTM effectively. As a result, current collection efficiency was enhanced at FTO electrode. The best perovskite cell with ED-BL achieved a higher power conversion efficiency of 13.6% that is higher than SC-BL one of 10.4% by approximately 30%.