Identifying Dominant Recombination Mechanisms in Perovskite Solar Cells by Measuring the Transient Ideality Factor
Identifying Dominant Recombination Mechanisms in Perovskite Solar Cells by Measuring the Transient Ideality Factor
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DOI：
10.1103/physrevapplied.11.044005
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发表时间：
2019-04-02
影响因子：
4.6
通讯作者：
Barnes, Piers Rf
中科院分区：
文献类型：
--
作者：
Calado, Phil;Burkitt, Dan;Barnes, Piers Rf
通过测量作为光强度的函数的开路电压（V-OC）来确定的光理想因子通常用于识别太阳能电池中的主导复合机制。将这种“Suns-V-OC”技术应用于钙钛矿电池是有问题的，因为V-OC以取决于先前施加的偏压（V-pre）、偏压光强度、器件架构和处理路线的方式随时间演变。在这里，我们表明，占主导地位的重组机制在两个结构相似的CH 3 NH3 PbI 3装置含有介孔Al 2 O3或TiO 2层，可以确定从签名的瞬态理想因子应用程序的正向偏置，V-前的设备在黑暗中。瞬态理想因子通过监测在不同光强度下作为时间的函数的V-OC的演变来测量。使用这种技术发现的理想性的初始值是一致的，从光致发光与光强度和电致发光与电流密度的测量获得的理想性因子的估计。模型化的设备上的测量，其中包括移动的离子电荷的影响的时间依赖性模拟，揭示了该初始值可以相关到现有的零维模型，而稳态值必须考虑到整个吸收层的载流子种群的均匀性进行分析。分析表明，通过电荷收集界面处的深陷阱的Shockley-Read-Hall（SRH）复合在被测器件的两种结构中占主导地位。使用瞬态光电压测量直接照射双面设备，我们进一步表明，钙钛矿电子传输层的界面延伸到整个介孔TiO 2层，与对应于SRH重组在大部分的膜的瞬态理想签名一致。这种方法将有助于识别钙钛矿和其他混合离子-电子导电钙钛矿太阳能电池的替代变体中的性能瓶颈。
The light ideality factor determined by measuring the open-circuit voltage (V-OC) as a function of light intensity is often used to identify the dominant recombination mechanism in solar cells. Applying this "Suns-V-OC" technique to perovskite cells is problematic since the V-OC evolves with time in a way that depends on the previously applied bias (V-pre), bias light intensity, device architecture and processing route. Here, we show that the dominant recombination mechanism in two structurally similar CH3 NH3PbI3 devices containing either mesoporous Al2O3 or TiO2 layers can be identified from the signature of the transient ideality factor following application of a forward bias, V-pre to the device in the dark. The transient ideality factor is measured by monitoring the evolution of V-OC as a function of time at different light intensities. The initial values of ideality found using this technique are consistent with estimates of the ideality factor obtained from measurements of photoluminescence vs light intensity and electroluminescence vs current density. Time-dependent simulations of the measurement on modeled devices, which include the effects of mobile ionic charge, reveal that this initial value can be correlated to an existing zero-dimensional model while steady-state values must be analyzed taking into account the homogeneity of carrier populations throughout the absorber layer. The analysis shows that Shockley-Read-Hall (SRH) recombination through deep traps at the charge-collection interfaces is dominant in both architectures of measured device. Using transient photovoltage measurements directly following illumination on bifacial devices, we further show that the perovskite-electron-transport-layer interface extends throughout the mesoporous TiO2 layer, consistent with a transient ideality signature corresponding to SRH recombination in the bulk of the film. This method will be useful for identifying performance bottlenecks in alternative variants of perovskite and other mixed ionic-electronic conducting absorber-based solar cells.