Enhanced performance of CH3NH3PbI3−xClx perovskite solar cells by CH3NH3I modification of TiO2-perovskite layer interface

摘要

In this work, perovskite solar cells (PSCs) with CH3NH3PbI3-xClx as active layer and spiro-OMeTAD as hole-transport media have been fabricated by one-step method. The methylammonium iodide (CH3NH3I) solution with different concentrations is used to modify the interface between mesoporous TiO2 (meso-TiO2) film and CH3NH3PbI3−xClx perovskite layer. Several techniques including X-ray diffraction, scanning electron microscopy, optical absorption, electrochemical impedance spectroscopy (EIS) and photoluminescence are used to investigate the effect of the interfacial modification. It is found that the interfacial modification by CH3NH3I enhance the crystallinity and increase the grain size of CH3NH3PbI_3−xCl_x layer, and improve the surface wetting properties of perovskite precursor on meso-TiO₂ film. The sunlight absorption and external quantum efficiency of PSCs in the visible region with wavelength less than 600 nm have been improved. The Nyquist plots obtained from the EIS suggest that the CH₃NH₃I modification can reduce the charge recombination rates. The photoluminescence measurement shows that the exciton dissociation in the modified devices is more effective than that in the control samples. The photovoltaic performance of the modified devices can be significantly improved with respect to the reference (control) devices. The CH₃NH₃I modified devices at the optimized concentration demonstrate the average power conversion efficiency of 12.27 % in comparison with the average efficiency of 9.68 % for the reference devices.Electronic supplementary materialThe online version of this article (doi:10.1186/s11671-016-1540-4) contains supplementary material, which is available to authorized users.