In methylammonium lead iodide (MAPbI₃), a slow recombination process of photogenerated carriers has often been considered to be the most intriguing property of the material resulting in high-efficiency perovskite solar cells. In spite of intense research over a decade or so, a complete understanding of carrier recombination dynamics in MAPbI₃ has remained inconclusive. In this regard, several microscopic processes have been proposed so far in order to explain the slow recombination pathways (both radiative and non-radiative), such as the existence of shallow defects, a weak electron–phonon coupling, presence of ferroelectric domains, screening of band-edge charges through the formation of polarons, occurrence of the Rashba splitting in the band(s), and photon-recycling in the material. Based on the up-to-date findings, we have critically assessed each of these proposals/models to shed light on the origin of a slow recombination process in MAPbI₃. In this review, we have presented the interplay between the mechanisms and our views/perspectives in determining the likely processes, which may dictate the recombination dynamics in the material. We have also deliberated on their interdependences in decoupling contributions of different recombination processes.

中文翻译：

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CH3NH3PbI3 中的载流子重组：为什么它是一个缓慢的过程？

在甲基碘化铅 (MAPbI ₃ ) 中，光生载流子的缓慢复合过程通常被认为是该材料最有趣的特性，可用于制造高效钙钛矿太阳能电池。尽管进行了十多年左右的深入研究，但对 MAPbI _{3中载流子重组动力学的全面了解}一直没有定论。在这方面，到目前为止已经提出了几个微观过程来解释缓慢的复合路径（辐射和非辐射），例如浅层缺陷的存在、弱电子-声子耦合、铁电畴的存在、筛选通过极化子的形成、带中 Rashba 分裂的发生以及材料中的光子循环来产生带边电荷。根据最新发现，我们对这些建议/模型中的每一个进行了严格评估，以阐明 MAPbI _{3中缓慢重组过程的起源}. 在本次审查中，我们介绍了机制与我们在确定可能过程中的观点/观点之间的相互作用，这可能决定了材料中的重组动力学。我们还讨论了它们在不同重组过程的解耦贡献中的相互依赖性。