利用电吸收探测混合钙钛矿太阳能电池中内电场屏蔽的动力学
The dynamics of internal electric field screening in hybrid perovskite solar cells probed using electroabsorption
摘要：
由金属卤化物钙钛矿太阳能电池中的电荷分布引起的电场对于理解这些设备所显示的许多奇怪而奇妙的光电特性至关重要。移动离子缺陷被认为在界面处积累以在施加外部偏压时屏蔽钙钛矿半导体的本体内的电场，但是需要工具来直接探测该过程中的电场的动态。在这里，我们表明，电吸收测量允许在活性层内的电场被跟踪作为频率或时间的函数。对应于钙钛矿层中的电场强度的电吸收信号的幅度对于外部施加的低频电压或在电压阶跃之后的长时间下降。我们的观察是一致的漂移扩散模拟，阻抗谱，瞬态光电流测量。它们表明在10 ms至100 s的时间尺度上的电荷屏蔽/再分布，这取决于器件夹层材料、钙钛矿组合物、主要带电缺陷和照明条件。该方法可以在典型的太阳能电池结构上进行，并有可能成为优化混合钙钛矿器件的常规表征工具。
英文摘要：
Electric fields arising from the distribution of charge in metal halide perovskite solar cells are critical for understanding the many weird and wonderful optoelectronic properties displayed by these devices. Mobile ionic defects are thought to accumulate at interfaces to screen electric fields within the bulk of the perovskite semiconductor on application of external bias, but tools are needed to directly probe the dynamics of the electric field in this process. Here we show that electroabsorption measurements allow the electric field within the active layer to be tracked as a function of frequency or time. The magnitude of the electroabsorption signal, corresponding to the strength of the electric field in the perovskite layer, falls off for externally applied low frequency voltages or at long times following voltage steps. Our observations are consistent with drift-diffusion simulations, impedance spectroscopy, and transient photocurrent measurements. They indicate charge screening/redistribution on time-scales ranging from 10 ms to 100 s depending on the device interlayer material, perovskite composition, dominant charged defect, and illumination conditions. The method can be performed on typical solar cell structures and has potential to become a routine characterization tool for optimizing hybrid perovskite devices.
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