Interpretation of inverted photocurrent transients in organic lead halide perovskite solar cells: proof of the field screening by mobile ions and determination of the space charge layer widths
Interpretation of inverted photocurrent transients in organic lead halide perovskite solar cells: proof of the field screening by mobile ions and determination of the space charge layer widths
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DOI：
10.1039/c6ee02914k
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发表时间：
2017-01-01
影响因子：
32.5
通讯作者：
O'Regan, Brian C.
中科院分区：
文献类型：
--
作者：
Belisle, Rebecca A.;Nguyen, William H.;O'Regan, Brian C.
在碘化甲基铵铅（NaI）钙钛矿太阳能电池中，已经提出由移动的离子屏蔽内建场是在许多电池中的电流/电压扫描中观察到的大滞后的原因的一部分。我们表明，光电流瞬态测量电压阶跃后立即（例如100亩）可以提供直接的证据，这场屏蔽存在。就在正向偏置的步骤之后，光电流瞬变在符号上反转（即，反转），并且反转的瞬变的幅度可以用于找到与电极相邻的空间电荷层的宽度的上限。这反过来又提供了一个移动的电荷浓度的下限，我们发现它大于或接近1 × 10（17）cm（-3）。使用一个新的光电流瞬态实验，我们表明，空间电荷层的厚度保持近似恒定的偏置的函数，预期在固体电解质中的移动的离子。我们还讨论了额外的特点，意味着一个异常稳定的深陷阱，或光电效应的移动的离子电导率的反转光电流瞬变。
In Methyl Ammonium Lead Iodide (MAPI) perovskite solar cells, screening of the built-in field by mobile ions has been proposed as part of the cause of the large hysteresis observed in the current/ voltage scans in many cells. We show that photocurrent transients measured immediately (e.g. 100 mu s) after a voltage step can provide direct evidence that this field screening exists. Just after a step to forward bias, the photocurrent transients are reversed in sign (i.e. inverted), and the magnitude of the inverted transients can be used to find an upper bound on the width of the space charge layers adjacent to the electrodes. This in turn provides a lower bound on the mobile charge concentration, which we find to be greater than or similar to 1 x 10(17) cm(-3). Using a new photocurrent transient experiment, we show that the space charge layer thickness remains approximately constant as a function of bias, as expected for mobile ions in a solid electrolyte. We also discuss additional characteristics of the inverted photocurrent transients that imply either an unusually stable deep trapping, or a photo effect on the mobile ion conductivity.