The Study Of The Effects Of The Interface Charge Of Perovskite Solar Cells On Performance Of The Devices And Organic-inorganic Perovskite Light-emitting Electrochemical Cells

Low-temperature solution-processed organic-inorganic halide perovskites have drawn worldwide attention due to their remarkable performance in photovoltaic devices. The high energy conversion efficiency is attributed to their long carrier lifetimes and high photoluminescence efficiencies of the hybrid perovskites. At present, the highest efficiency of organic inorganic perovskite solar cell is more than 20%. Recently, the materials also demonstrate interesting light-emitting properties. In this paper, the work mainly on the effect of the interface charge on device performance of perovskite solar cells and study on Organic-inorganic perovskite light-emitting electrochemical cells:1. The accumulation of mobile ions causes space charge at interfaces in perovskite solar cells. There is a slow dynamic process of ion redistribution when the bias is changed. The interface charge affects the band bending and thus the photocurrent of the solar cells. Consequently the dynamic process of the interface charge governs the current-voltage hysteresis. Very low interface charge density leads to hysteresis-free devices.2. While perovskite light-emitting diodes made from high workfunction anode and low workfunction cathode have recently gained intense interests, we demonstrate perovskite light-emitting devices from two high workfunction electrodes with interesting features. Firstly, electroluminescence can be easily obtained from both forward and reverse biases. Secondly, the results of impedance spectroscopy indicate that the ionic conductivity in the iodide perovskite (CH3NH3PbI3) is large with a value of ～10-8 Scm"1. Thirdly, the shift of the emission spectrum in the mixed halide perovskite (CH3NH3PbI3-xBrx) light-emitting devices indicates that I-ions are mobile in the perovskites. Fourthly, our work shows that the accumulated ions at the interfaces results in a large capacitance (～100 μFcm-2). The above results conclusively prove that the organic-inorganic halide perovskites are solid electrolytes with mixed ionic and electronic conductivity and the light-emitting device is a light-emitting electrochemical cells. The work also suggests that the organic-inorganic halide perovskites are potential energy-storage materials, which may be applicable in the field of solid-state supercapacitors and batteries.