Decreasing Charge Losses in Perovskite Solar Cells Through the 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 (Voc), device reproducibility, and the relationship between the increase in Voc, and the presence of the Al2O3 layer is thoroughly discussed and explained. Although in DSSC there is a TiO2 conduction band edge shift for Al2O3coated 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.