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 TiO 2 (mp-TiO 2 ) interface, we modified the methylammonium lead iodide (MAPI) /mp-TiO 2 interface with a nanoscopic layer of insulating Al 2 O 3 . The effects on device efficiency, the open-circuit voltage ( V oc ), device reproducibility, and the relationship between the increase in V oc, and the presence of the Al 2 O 3 layer is thoroughly discussed and explained. Although in DSSC there is a TiO 2 conduction band edge shift for Al 2 O 3 coated mp-TiO 2 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 Al 2 O 3 -treated samples, which improves the overall efficiency of the device because of the slower rate in the back-electron transfer reactions.