Methylammonium lead iodide (MAPI) cells of the design FTO/sTiO2/

mpTiO2/MAPI/Spiro-OMeTAD/Au, where FTO is fluorine-doped tin oxide, sTiO2

indicates solid-TiO2, and mpTiO2 is mesoporous TiO2, are studied using transient

photovoltage (TPV), differential capacitance, charge extraction, current interrupt, and

chronophotoamperometry. We show that in mpTiO2/MAPI cells there are two kinds of

extractable charge stored under operation: a capacitive electronic charge (∼0.2 μC/

cm2) and another, larger charge (40 μC/cm2), possibly related to mobile ions.

Transient photovoltage decays are strongly double exponential with two time constants

that differ by a factor of ∼5, independent of bias light intensity. The fast decay (∼1 μs

at 1 sun) is assigned to the predominant charge recombination pathway in the cell. We

examine and reject the possibility that the fast decay is due to ferroelectric relaxation or

to the bulk photovoltaic effect. Like many MAPI solar cells, the studied cells show

significant J−V hysteresis. Capacitance vs open circuit voltage (Voc) data indicate that

the hysteresis involves a change in internal potential gradients, likely a shift in band

offset at the TiO2/MAPI interface. The TPV results show that the Voc hysteresis is not due to a change in recombination rate

constant. Calculation of recombination flux at Voc suggests that the hysteresis is also not due to an increase in charge separation

efficiency and that charge generation is not a function of applied bias. We also show that the J−V hysteresis is not a light driven

effect but is caused by exposure to electrical bias, light or dark.