Tang Jianbo, Tian Wenming, Sun Fengke, Sun Qi, Leng Jing, Zhao Shengli, Jin Shengye
State Key Laboratory of Molecular Reaction Dynamics and the Dynamic Research Center for Energy and Environmental Materials, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, China.
University of Chinese Academy of Sciences, Beijing 100049, China.
J Phys Chem Lett. 2023 Mar 23;14(11):2800-2806. doi: 10.1021/acs.jpclett.3c00332. Epub 2023 Mar 12.
The phase segregation in mixed halide perovskites is recently found to improve the photoluminescence quantum yield (PLQY) of the perovskites by concentrating the carriers. However, how phase segregation affects the photoinduced carrier dynamics is unclear. Herein, we find that the phase segregation in CHNHPbBrI mixed halide perovskite thin film is morphology-dependent by showing I-rich domains mainly along the grain boundaries. Ultrafast transient absorption (TA) and photoluminescence upconversion (PL-UC) spectroscopy measurements uncover that the carrier accumulation in the low energy I-rich domains includes two carrier transfer pathways. Carrier transfer from the Br-rich domain and the mixed phase to the I-rich domain is realized by consecutive hole (∼0.5 ps) and electron (<12.4 ps) transfer and energy transfer (<12.4 ps), respectively. The finding reveals the carrier funneling dynamic mechanism in phase-segregated halide perovskite films and provides a guideline for the applications of mixed halide perovskites in color-conversion devices or high-efficiency LEDs.
最近发现，混合卤化物钙钛矿中的相分离通过载流子聚集提高了钙钛矿的光致发光量子产率（PLQY）。然而，相分离如何影响光致载流子动力学尚不清楚。在此，我们发现CHNHPbBrI混合卤化物钙钛矿薄膜中的相分离与形态有关，表现为富碘区域主要沿晶界分布。超快瞬态吸收（TA）和光致发光上转换（PL-UC）光谱测量表明，低能量富碘区域中的载流子积累包括两条载流子转移途径。从富溴区域和混合相到富碘区域的载流子转移分别通过连续的空穴转移（约0.5皮秒）和电子转移（<12.4皮秒）以及能量转移（<12.4皮秒）实现。这一发现揭示了相分离卤化物钙钛矿薄膜中的载流子漏斗动力学机制，并为混合卤化物钙钛矿在颜色转换器件或高效发光二极管中的应用提供了指导。
