Overcoming Bulk Recombination Limits of Layered Perovskite Solar Cells with Mesoporous Substrates

The synthesis and characterization of a lead iodide layered perovskite, [NH2C(I)=NH2](2)(CH3NH3)(2)Pb2I8, is described. The combination of an ideal bandgap of 1.61 eV and excellent compositional stability under ambient conditions make it a promising candidate for integration in solar cells. Planar solar cells utilizing [NH2C(I)=NH2](2)(CH3NH3)(2)Pb2I8 exhibit two interesting phenomena in the photovoltaic performance: an exponential dependence of Lc on incident light intensity and abnormal J-V response. To investigate the photophysical properties of [NH2C(I)=NH2](2)(CH3NH3)(2)Pb2I8 perovskite planar solar cells, intensity-modulated photocurrent spectroscopy (IMPS) and electrochemical impedance spectroscopy (EIS) were conducted. It is found that the planar structured solar cells of the layered perovskite suffer from bulk recombination which limits the charge collection and photocurrent. Use of a mesoporous TiO2 scaffold layer largely overcomes the recombination limitations of the layered perovskite and significantly improves the photovoltaic performance.