Acoustic-optical phonon up-conversion and hot-phonon bottleneck in lead-halide perovskites.
Acoustic-optical phonon up-conversion and hot-phonon bottleneck in lead-halide perovskites.
复制标题
声学声子上转化和铅孔孔孔孔的热孔瓶瓶颈。
DOI：
10.1038/ncomms14120
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发表时间：
2017-01-20
影响因子：
16.6
通讯作者：
Conibeer G
中科院分区：
文献类型：
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作者：
Yang J;Wen X;Xia H;Sheng R;Ma Q;Kim J;Tapping P;Harada T;Kee TW;Huang F;Cheng YB;Green M;Ho-Baillie A;Huang S;Shrestha S;Patterson R;Conibeer G
卤化铅钙钛矿（APbX3）中的热声子瓶颈效应延长了热电荷载流子的冷却周期，这一效应可用于下一代光伏器件。本研究利用超快光学表征和第一性原理计算，比较了四种卤化铅钙钛矿（A=FA+/MA+/Cs+， X=I−/Br−）内部的载流子-声子动力学。在这里，我们发现混合钙钛矿中的声子瓶颈效应比无机钙钛矿中的声子瓶颈效应更强。与铯基体系相比，FAPbI3的载流子-声子弛豫速率降低了10倍。低能声子的上转换被认为是造成瓶颈效应的原因。有机阳离子的存在引入了重叠声子分支，促进了低能模式的上跃迁。声子传播的阻断与材料的超低导热性相关，也增加了整体上转换效率。这一结果也为在材料中实现长寿命热载流子提供了一种新的通用方法。卤化铅钙钛矿热电荷载流子的缓慢冷却可用于光伏器件。在这里，Yang等人通过瞬态吸收光谱研究了热载流子动力学。他们将声子瓶颈与低能量声子的上转换联系起来，这是由有机阳离子的存在促进的。
The hot-phonon bottleneck effect in lead-halide perovskites (APbX3) prolongs the cooling period of hot charge carriers, an effect that could be used in the next-generation photovoltaics devices. Using ultrafast optical characterization and first-principle calculations, four kinds of lead-halide perovskites (A=FA+/MA+/Cs+, X=I−/Br−) are compared in this study to reveal the carrier-phonon dynamics within. Here we show a stronger phonon bottleneck effect in hybrid perovskites than in their inorganic counterparts. Compared with the caesium-based system, a 10 times slower carrier-phonon relaxation rate is observed in FAPbI3. The up-conversion of low-energy phonons is proposed to be responsible for the bottleneck effect. The presence of organic cations introduces overlapping phonon branches and facilitates the up-transition of low-energy modes. The blocking of phonon propagation associated with an ultralow thermal conductivity of the material also increases the overall up-conversion efficiency. This result also suggests a new and general method for achieving long-lived hot carriers in materials. Slow cooling of hot charge carriers in lead halide perovskite could be used in photovoltaics devices. Here, Yang et al. study hot carrier dynamics by transient absorption spectroscopy. They relate the phonon bottleneck to the up-conversion of low-energy phonons, facilitated by the presence of organic cations.