11% Efficient Perovskite Solar Cell Based on ZnO Nanorods: An Effective Charge Collection System

A perovskite solar cell based on ZnO nanorods was prepared, and its photovoltaic performance was investigated. ZnO nanorods were grown on the ZnO seed layer from solution, and their diameters and lengths were controlled by precursor concentration and growth time. CH3NH3PbI3 perovskite infiltrated ZnO nanorods showed a power conversion efficiency of 11.13% with short-circuit current density Jsc of 20.08 mA/cm2, open-circuit voltage Voc of 991 mV and fill factor of 0.56. Square spectral feature of external quantum efficiency (EQE) was observed, where EQE exceeded 80% in almost the entire wavelength range from 400 to 750 nm, and the integrated current density of 20.03 mA/cm2 calculated from EQE data was in good agreement with the observed Jsc. Compared to the perfect spectral response of ZnO nanorods, a perovskite solar cell based on TiO2 nanorods exhibited an integrated current density (16 mA/cm2) much lower than the measured Jsc (20.9 mA/cm2). In addition, time-limited photocurrent response under 530 and 700 nm monochromatic beams at 10 Hz showed that device signal amplitude, associated with charge collection, was rapidly saturated for the ZnO nanorod-based device whereas charge collection was not fully detected for the TiO2 nanorod-based device because of slow collection rate. The current results suggest that ZnO nanorod is an effective charge collection system in CH3NH3PbI3 based perovskite solar cells.