Decreasing Charge Losses in Perovskite Solar Cells Through mp-TiO₂/MAPI Interface Engineering

On the basis of our experience in controlling the recombination kinetics in Dye Sensitized Solar Cells (DSSC) by modifying the mesoporous TiO₂ (mp-TiO₂) interface, we modified the methylammonium lead iodide (MAPI) /mp-TiO₂ interface with a nanoscopic layer of insulating Al₂O₃. The effects on device efficiency, the open-circuit voltage (<i>V</i>_oc), device reproducibility, and the relationship between the increase in <i>V</i>_oc, and the presence of the Al₂O₃ layer is thoroughly discussed and explained. Although in DSSC there is a TiO₂ conduction band edge shift for Al₂O₃ coated mp-TiO₂ films, in MAPI perovskite solar cells the charge vs voltage measurements carried out under sun-simulated irradiation conditions show a negligible shift of the exponential charge distribution whether it is measured using PICE (Photo Induced Charge Extraction) or PIDC (Photo Induced Differential Charging). Furthermore, the charge recombination lifetime decreases considerably in the Al₂O₃-treated samples, which improves the overall efficiency of the device because of the slower rate in the back-electron transfer reactions