2-Methylimidazole as an interlayer for the enhancement of the open-circuit voltage in perovskite solar cells

The loss of open-circuit voltage is a major obstacle for approaching the theoretical value of the power conversion efficiency in hybrid perovskite solar cells. In this study, a feasible and effective strategy for modifying the interface between the perovskite and the mesoporous TiO2 layer is proposed and implemented for the first time using 2-methylimidazole as a coating layer. As a result, the open-circuit voltage in the perovskite solar cells is significantly improved by 80 mV. The electronic impedance spectroscopy and photoluminescence spectroscopy results demonstrate that the modification of 2-methylimidazole as an interfacial insulating layer suppresses the electron transfer back from the anode electrode to the perovskite active layer, thereby inhibiting the recombination of the carriers at the interfaces, which results in an enhancement of the open-circuit voltage in the device. The cell modified with 2-methylimidazole shows increases in the open-circuit voltage from 1.05 to 1.13 V and in the power conversion efficiency from 17.48% to 19.45%. The optimal device with an area of 1 cm2 also exhibits an impressive efficiency of 16.38%.