Effects of electron- and hole-current hysteresis on trap characterization in organo-inorganic halide perovskite

Charge trap density and carrier mobility of perovskite materials are the critical properties of perovskite solar cells. The space charge limited current (SCLC) method, which measures a dark current–voltage (I-V) curve of a single-carrier device has found extensive use for studying the trap density and charge carrier mobility in perovskite materials. Herein, it was found that the electron- and hole-current in organo-lead perovskite-based single-carrier device undergoes significant hysteresis under forward and reverse scanning due to the mobile ions. In addition, it was also observed that measuring history has a detrimental effect on hysteresis resulting in possible overestimation or underestimation of the extracted electrical values from the SCLC measurement. In the forward/reverse scanning process, the mobile ionic defects enhance/shield the charge in the traps due to ionic charging/discharging, thereby increasing/reducing the interface barrier and net charge in the I-V scanning, which in turn affects the determination of transport properties of the carrier. These results raise quite a few doubts over the direct application of classical SCLC measurements for the accurate characterization of intrinsic transport properties of the mixed ionic-electronic perovskite.