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Transient Photovoltage in Perovskite Solar Cells: Interaction of Trap-Mediated Recombination and Migration of Multiple Ionic Species
The Journal of Physical Chemistry C ( IF 3.7 ) Pub Date : 2018-05-07 00:00:00 , DOI: 10.1021/acs.jpcc.8b02529
Daniel Walter 1 , Andreas Fell 2, 3 , Yiliang Wu 1 , The Duong 1 , Chog Barugkin 1 , Nandi Wu 1 , Thomas White 1 , Klaus Weber 1
Affiliation  

It is highly probable that perovskite solar cells (PSCs) are mixed electronic-ionic conductors, with ion migration being the driving force for PSC hysteresis. However, there is much that is not understood about the interaction of ion migration with other processes in the cell. The key question is: what factors of a PSC are influenced when ions are free to move? In this contribution, we employ a numerical drift-diffusion model of PSCs to show that the migration of both anions and cations in interaction with trap-mediated recombination in the bulk and/or at the surfaces of the perovskite absorber can manifest both current–voltage hysteresis and unusual nonmonotonic PSC photovoltage transients. We identify that a key mechanism of this interaction is the influence of the net ionic charge throughout the perovskite bulk—which varies as the ions approach new steady-state conditions—on the distribution of electrons and holes and subsequently the spatial distribution of trap-mediated recombination modeled after Shockley Read Hall (SRH) statistics. Relative to intrinsic recombination mechanisms, SRH recombination can be highly sensitive to local asymmetries of the electron–hole population. We show that this sensitivity is key to replicating nonmonotonic transients with multiple time constants, the forms of which may have suggested multiple processes. This work therefore supports the conceptualization of the hysteretic behavior of PSCs as dominated by the interplay between ion migration and trap-mediated recombination throughout the perovskite absorber.

中文翻译:

钙钛矿太阳能电池中的瞬态光电压:陷阱介导的重组和多种离子物种迁移的相互作用。

钙钛矿太阳能电池(PSC)很可能是混合的电子离子导体,而离子迁移是PSC滞后的驱动力。但是,关于离子迁移与细胞中其他过程的相互作用,还有很多事情尚不为人所知。关键问题是:当离子自由移动时,PSC的哪些因素会受到影响?在此贡献中,我们采用了PSC的数值漂移扩散模型,表明在钙钛矿吸收剂的整体和/或表面,阴离子和阳离子的迁移与陷阱介导的重组相互作用可以表现出电流-电压迟滞和异常的非单调PSC光电压瞬变。我们发现,这种相互作用的关键机制是整个钙钛矿块体中净离子电荷的影响(随着离子接近新的稳态条件而变化)对电子和空穴的分布以及随后陷阱陷阱介导的空间分布的影响。重组以Shockley Read Hall(SRH)统计数据为模型。相对于固有的重组机制,SRH重组对电子-空穴种群的局部不对称高度敏感。我们表明,这种敏感性是复制具有多个时间常数的非单调瞬变的关键,其形式可能表明存在多个过程。
更新日期:2018-05-07
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