Charge‐Carrier Trapping and Radiative Recombination in Metal Halide Perovskite Semiconductors,Advanced Functional Materials

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Charge‐Carrier Trapping and Radiative Recombination in Metal Halide Perovskite Semiconductors
Advanced Functional Materials ( IF 18.5 ) Pub Date : 2020-08-20 , DOI: 10.1002/adfm.202004312
Michael J. Trimpl _{1,

2} , Adam D. Wright ₁ , Kelly Schutt ₁ , Leonardo R. V. Buizza ₁ , Zhiping Wang ₁ , Michael B. Johnston ₁ , Henry J. Snaith ₁ , Peter Müller‐Buschbaum _{2,

3} , Laura M. Herz ₁

Affiliation

Trap‐related charge‐carrier recombination fundamentally limits the performance of perovskite solar cells and other optoelectronic devices. While improved fabrication and passivation techniques have reduced trap densities, the properties of trap states and their impact on the charge‐carrier dynamics in metal‐halide perovskites are still under debate. Here, a unified model is presented of the radiative and nonradiative recombination channels in a mixed formamidinium‐cesium lead iodide perovskite, including charge‐carrier trapping, de‐trapping and accumulation, as well as higher‐order recombination mechanisms. A fast initial photoluminescence (PL) decay component observed after pulsed photogeneration is demonstrated to result from rapid localization of free charge carriers in unoccupied trap states, which may be followed by de‐trapping, or nonradiative recombination with free carriers of opposite charge. Such initial decay components are shown to be highly sensitive to remnant charge carriers that accumulate in traps under pulsed‐laser excitation, with partial trap occupation masking the trap density actually present in the material. Finally, such modelling reveals a change in trap density at the phase transition, and disentangles the radiative and nonradiative charge recombination channels present in FA_0.95Cs_0.05PbI_3, accurately predicting the experimentally recorded PL efficiencies between 50 and 295 K, and demonstrating that bimolecular recombination is a fully radiative process.

中文翻译：

金属卤化物钙钛矿半导体中的载流子陷阱和辐射复合

与陷阱有关的电荷载流子复合从根本上限制了钙钛矿太阳能电池和其他光电设备的性能。尽管改进的制造和钝化技术降低了陷阱密度，但陷阱态的性质及其对金属卤化物钙钛矿中电荷载流子动力学的影响仍在争论中。在这里，给出了一个混合的form-铯-碘化铅钙钛矿混合体中的辐射和非辐射复合通道的统一模型，包括载流子的俘获，去俘获和积累以及更高阶的重组机制。脉冲光生后观察到的快速初始光致发光（PL）衰减分量被证明是由于自由载流子在未占据的陷阱状态下快速定位而导致的，随后可以进行去陷阱，或与相反电荷的自由载体进行非辐射重组。此类初始衰减分量显示出对在脉冲激光激发下聚集在阱中的残余电荷载流子高度敏感，部分阱的占据掩盖了材料中实际存在的阱密度。最后，这种建模揭示了在相变时陷阱密度的变化，并解开了FA中存在的辐射和非辐射电荷复合通道_0.95 Cs _0.05 PbI _3，准确地预测了实验记录的50至295 K之间的PL效率，并证明了双分子重组是完全辐射的过程。

更新日期：2020-10-17

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