<p>The electron and hole selective contact (SC) play a pivotal role in
the performance of perovskite solar cells. In order to separate the interfacial
phenomenon from bulk, the influence of charge SC was elucidated, by means of impedance
spectroscopy. The specific role played by TiO<sub>2</sub> and <i>Spiro-OMeTAD</i>
as electron and hole SC in perovskite solar cells was investigated at short circuit condition at
different temperatures. We have probed MAPbI<sub>3</sub> and (FAPbI<sub>3</sub>)<sub>0.85</sub>(MAPbBr<sub>3</sub>)<sub>0.15
</sub>and elucidated parameters such as charge carrier mobility, recombination
resistance, time constant and charge carrier kinetics in perovskite layer and
at the interface of perovskite/SC. Charge carrier mobility in mixed perovskite
was found to be nearly two order of magnitude higher as compared to MAPbI<sub>3</sub>.
Moreover, the carrier mobility in devices with only electron SC was found to be
higher as compared only hole SC. The charge accumulation at TiO<sub>2</sub>/perovskite/<i>Spiro</i>-OMeTAD
interfaces were studied via frequency dependent capacitance, revealing higher
charge accumulation at perovskite/S<i>piro</i>-OMeTAD than at TiO<sub>2</sub>/perovskite
interface. By performing varying temperature frequency dependent capacitance measurements
the distribution of density of state within the bandgap of the perovskites, the
emission rate of electrons from the trap states and traps activation energy was
determined. </p>
Study of charge-carrier relaxation in a disordered organic semiconductor by simulating impedance spectroscopy