Charge transport in bulk CH3NH3PbI3 perovskite

Abstract

The variation of leakage current and polarization hysteresis properties for bulk CH3NH3PbI3 perovskite was studied as a function of temperature to understand the reported hysteresis in photocurrent and the role of ferroelectricity. The leakage current decreased by two orders of magnitude when the temperature was lowered from 350 K to 100 K. The transitions in leakage current were observed at structural phase transition temperatures. The temperature dependence study allowed the identification of current conduction mechanism based on various models for ferroelectrics and insulating materials. Our results show that the leakage current is governed by the space charge limited conduction mechanism which should be considered in addition to ion conduction and ferroelectricity when analyzing current-voltage hysteresis for thin film and bulk materials. The Mott's variable range hopping model fits well to the experimental data indicating the charge conduction is through hopping mechanism from 300 K to 160 K and possibly tunneling below 160 K. The conclusions from polarization hysteresis study are: (1) the hysteresis loop shape is highly dependent upon frequency and show non-saturating behavior, an indicative of strong non-ferroelectric contributions such as resistive component. (2) No domain switching current was observed between the temperature range of 100 K–350 K. (3) An electric field off-set was observed in polarization-electric field curves and it was dependent upon the frequency and temperature. This offset could be caused by the accumulation of vacancies at one interface, which could give rise to hysteresis in forward and reverse bias photocurrent. (4) The time dependence study of instantaneous current as the voltage was increased linearly show strong resistive contribution to hysteresis loop at temperatures above 200 K and capacitive contribution at 100 K.